Copy/blog/800204
All the following contents are collected online:
FreeMarker's template file is not much more complicated than HTML pages. FreeMarker template file is mainly composed of the following 4 parts:
1. Text: the direct output part
2. Comment: <#-- ... --> format part, will not output
3. Interpolation: i.e. the part of the format ${...} or #{...} will be used instead of the output in the data model.
4. FTL instruction: FreeMarker is specified, similar to HTML tags, and the name is added to distinguish it, and it will not be output.
Below is an example of the FreeMarker template, including the 4 parts mentioned above
<html><br>
<head><br>
<title>Welcome!</title><br>
</head><br>
<body><br>
<#-- Comments section --><br>
<#-- Use interpolation below -->
<h1>Welcome ${user} !</h1><br>
<p>We have these animals:<br>
<u1><br>
<#-- Use FTL instruction -->
<#list animals as being><br>
<li>${} for ${} Euros<br>
<#list><br>
<u1><br>
</body><br>
</html>
1. FTL instruction rules
In FreeMarker, using FTL tags to use instructions. FreeMarker has 3 types of FTL tags, which are exactly similar to HTML tags.
1. Start tag: <#directivename parameter>
2. End tag:</#directivename>
3. Empty tag:<#directivename parameter/>
In fact, the previous symbol # when using the tag may also become @. If the instruction is a user instruction rather than a built-in instruction in the system, the # symbol should be changed to the @ symbol.
When using FTL tags, there should be correct nesting instead of cross-using, which is exactly the same as XML tag usage. If you use non-existent directives, FreeMarker will not use the template output, but will generate an error message. FreeMarker will ignore whitespace characters in the FTL tag. It is worth noting that whitespace characters are not allowed between < , /> and directives.
2. Interpolation rules
FreeMarker interpolation has the following two types: 1, general interpolation ${expr}; 2, digital format interpolation: #{expr} or #{expr;format}
2.1 General Interpolation
For general interpolation, it can be divided into the following 4 situations:
1. The interpolation result is a string value: Direct output expression result
2. The interpolation result is a numeric value: convert the expression result into text output according to the default format (setting by the #setting directive). Single interpolation can be formatted using the built-in string function, as shown in the following example:
<#settion number_format="currency"/>
<#assign answer=42/>
${answer}
${answer?string} <#-- the same as ${answer} -->
${answer?}
${answer?}
${answer?}
${answer}
The output result is:
$42.00
$42.00
42
$42.00
4,200%
3. The interpolation result is a date value: convert the expression result into text output according to the default format (setting by the #setting directive). Single interpolation can be formatted using the built-in string function, as shown in the following example:
${lastUpdated?string("yyyy-MM-dd HH:mm:ss zzzz")}
${lastUpdated?string("EEE, MMM d, ''yy")}
${lastUpdated?string("EEEE, MMMM dd, yyyy, hh:mm:ss a '('zzz')'")}
The output result is:
2008-04-08 08:08:08 Pacific Daylight Time
Tue, Apr 8, '03
Tuesday, April 08, 2003, 08:08:08 PM (PDT)
4. The interpolation result is a boolean value: convert the expression result into text output according to the default format (setting by the #setting directive). Single interpolation can be formatted using the built-in string function, as shown in the following example:
<#assign foo=true/>
${foo?string("yes", "no")}
The output result is:
yes
2.2 Digital formatting interpolation
Number format interpolation can be used in the form of #{expr;format} to format numbers, where format can be:
mX: The smallest X digit of the fractional part
MX: The maximum X digit of the decimal part
As in the following example:
<#assign x=2.582/>
<#assign y=4/>
#{x; M2} <#- Output 2.58 -->
#{y; M2} <#- Output 4 -->
#{x; m2} <#- Output 2.6 -->
#{y; m2} <#- Output 4.0 -->
#{x; m1M2} <#- Output 2.58 -->
#{x; m1M2} <#- Output 4.0 -->
3. Expressions
Expressions are the core function of the FreeMarker template. When an expression is placed in the interpolation syntax ${}, it indicates that the value of the expression needs to be output; the expression syntax can also be combined with the FreeMarker tag to control the output. In fact, FreeMarker's expression function is very powerful. It not only supports direct specifying values and outputting variable values, but also supports string formatted output and collection access.
3.1 Specify the value directly
Use the direct value specifying syntax to let FreeMarker output the values in the interpolated value directly, rather than outputting variable values. The direct value specified can be strings, numeric values, boolean values, collections, and MAP objects.
1, string
Directly specifying the string value is limited by single or double quotes. If the string value contains special characters and needs to be escaped, see the following example:
${"My file is saved in C:\\Disk"}
${'My name is \"annlee\"'}
The output result is:
My file is saved in C:\disk
My name is "annlee"
FreeMarker supports the following escape characters:
\";Double quotes (u0022)
\';Single quotes (u0027)
\\;Backslash(u005C)
\n;Line Break(u000A)
\r;Enter(u000D)
\t;Tab(u0009)
\b;Backspace key (u0008)
\f;Form feed(u000C)
\l;<
\g;>
\a;&
\{;{
\xCode; directly specify the Unicode code through a 4-digit hexadecimal number, and output the characters corresponding to the unicode code.
If a paragraph of text contains a large number of special symbols, FreeMarker provides another special format: you can add r marks before the quotation marks of the specified string content, and the file after the r mark will be directly output. See the following code:
${r"${foo}"}
${r"C:\foo\bar"}
The output result is:
${foo}
C:\foo\bar
2, value
The values in the expression are output directly without quotation marks. The decimal points are separated by ".", and groupings cannot be used. FreeMarker does not currently support scientific notation, so "1E3" is wrong. You need to pay attention to the following points when using numeric values in FreeMarker expressions:
1. The 0 before the decimal point cannot be omitted, so ".5" is the wrong way to write it
2, the values 8, +8, 8.00 are all the same
3, boolean value
Use true and false directly, without quotes.
4, collection
The set is included in square brackets, and the elements of each set are separated by English commas "," as shown in the following example:
<#list ["Monday", "Tuesday", "Thursday", "Friday", "Saturday", "Sunday"] as x>
${x}
</#list>
The output result is:
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
In addition, collection elements can also be expressions, examples are as follows:
[2 + 2, [1, 2, 3, 4], "whatnot"]
You can also use numeric ranges to define numeric sets, such as 2..5 is equivalent to [2, 3, 4, 5], but it is more efficient. Note that when using numeric ranges to define sets, there is no need to use square brackets, and numeric ranges also support inverse incremental numeric ranges, such as 5..2
5. Map object
Map objects use curly braces to include, the key-value pairs in the Map are separated by the English colon:" and the multiple sets of key-value pairs are separated by the English comma" and ". The following is an example:
{"Chinese":78, "Mathematics":80}
The key and value of the Map object are both expressions, but the key must be a string
3.2 Output variable value
When FreeMarker's expression outputs variables, these variables can be top-level variables, variables in Map objects, variables in sets, and can use point (.) syntax to access the properties of Java objects. These situations are discussed below.
1. Top variable
The so-called top-level variable is the value placed directly in the data model, for example, there is the following data model:
Map root = new HashMap(); //Create a data model
("name","annlee"); //name is a top-level variable
For top-level variables, use ${variableName} directly to output the variable value. The variable name can only be a combination of letters, numbers, underscores, $, @ and #, and cannot start with numbers. In order to output the value of the above name, the following syntax can be used:
${name}
2. Output collection elements
If you need to output a collection element, you can output the collection element according to the index of the collection element, and the index of the collection element is specified in square brackets. Suppose there is an index:
["Monday", "Tuesday", "Thursday", "Friday", "Saturday", "Sunday"]. The index is called week. If you need to output Wednesday, you can use the following syntax:
${week[2]} //Output the third collection element
In addition, FreeMarker also supports returning subsets of collections. If you need to return subsets of collections, you can use the following syntax:
week[3..5] //Returns a subset of the week set, the elements in the subset are the 4th to 6th elements in the week set
3. Output Map elements
The Map object here can be a direct HashMap instance, or even a JavaBean instance. For JavaBean instances, we can also regard it as a Map instance with a property key and an attribute value. In order to output the value of the Map element, you can use dot syntax or square bracket syntax. If there is the following data model:
Map root = new HashMap();
Book book = new Book();
Author author = new Author();
("annlee");
("gz");
("struts2");
(author);
("info","struts");
("book", book);
To access the name of the author of the book named struts2 in the data model, the following syntax can be used:
//Use all dot syntax
book["author"].name
["name"] //Mixed point syntax and square bracket syntax
book["author"]["name"] //Everything uses square bracket syntax
When using dot syntax, variable names have the same limitation as top-level variables, but square bracket syntax does not have this limitation because the name can be the result of any expression.
3.3, String operation
FreeMarker's expressions are very flexible in string operations, and can concatenate string constants and variables, or return substrings of strings, etc.
There are two syntaxes for string concatenation:
1. Use ${..} or #{..} to insert the value of the expression in the constant part of the string to complete the string concatenation.
2. Directly use the connection operator + to connect the string
For example, there is the following data model:
Map root = new HashMap(); ("user","annlee");
The following links the user variable and the constant:
${"hello, ${user}!"} //Use the first syntax to connect
${"hello, " + user + "!"} //Use the + sign to connect
The output strings above are all hello, annlee!, and it can be seen that the effects of these two syntaxes are exactly the same.
It is worth noting that ${..} can only be used for text parts and cannot be used for expressions. The following code is wrong:
<#if ${isBig}>Wow!</#if>
<#if "${isBig}">Wow!</#if>
It should be written as: <#if isBig>Wow!</#if>
Intercepting substrings can be performed based on the index of the string. When intercepting substrings, if only one index value is specified, it is used to obtain the characters corresponding to the specified index in the string; if two index values are specified, the string substring between the two indexes is returned. If there is the following data model:
Map root = new HashMap(); ("book","struts2,freemarker");
Substrings can be intercepted by the following syntax:
${book[0]}${book[4]} //The result is su
${book[1..4]} //The result is true
3.4 Collection connection operator
The set operator mentioned here is to connect two sets into a new set. The operator connecting the set is +, see the following example:
<#list ["Monday","Tuesday","Wednesday"] + ["Thursday","Friday","Saturday"] as x>
${x}
</#list>
The output is: Monday Tuesday Wednesday Thursday Friday Saturday Sunday
3.5 Map connection operator
The connection operator of the Map object also connects two Map objects into a new Map object. The connection operator of the Map object is +. If the two Map objects have the same key, the value on the right replaces the value on the left. See the following example:
<#assign scores = {"Chinese":86,"Mathematics":78} + {"Mathematics":87,"Java":93}>
Chinese score is ${scores.Chinese}
Mathematics score is ${scores.Mathematics}
Java score is ${}
The output result is:
Chinese score is 86
Mathematics score is 87
Java score is 93
3.6 Arithmetic operators
FreeMarker expression fully supports arithmetic operations. FreeMarker supports arithmetic operators: +, -, *, /, % See the following code:
<#assign x=5>
${ x * x - 100 }
${ x /2 }
${ 12 %10 }
The output result is:
-75 2.5 2
The following points should be paid attention to when using arithmetic operators in expressions:
1. The number of the operator on both sides must be a number
2. When using the + operator, if one side is a number and the other side is a string, the number will be automatically converted into a string and then connected, such as: ${3 + "5"}, the result is: 35
Use the built-in int function to round the numerical value, such as:
<#assign x=5>
${ (x/2)?int }
${ 1.1?int }
${ 1.999?int }
${ -1.1?int }
${ -1.999?int }
The result is: 2 1 1 -1 -1
3.7 Comparison operators
There are several comparison operators supported in expressions:
1,=or==: determine whether the two values are equal.
2,!=: Determine whether the two values are not equal.
3,>or gt: determine whether the left value is greater than the right value
4,>= or gte: determine whether the left value is greater than or equal to the right value
5,<or lt: determine whether the left value is smaller than the right value
6, <= or lte: determine whether the left value is less than or equal to the right value
Note: = and != can be used to compare whether the values and dates are equal, but the sides of = and != must be of the same type of value, otherwise an error will occur. Moreover, FreeMarker is an exact comparison, "x", "x", "X" are not equal. Other runners can act on numbers and dates, but cannot act on strings. Most of the time, using letter operators such as gt instead of > will have a better effect, because FreeMarker will interpret > as the end character of the FTL tag. Of course, brackets can also be used to avoid this situation, such as: <#if (x>y)>
3.8 Logical operators
There are several logical operators:
Logic and :&&
Logical or:||
Logical non:!
Logical operators can only act on boolean values, otherwise an error will be generated
3.9 Built-in functions
FreeMarker also provides some built-in functions to convert output, which can be followed by any variable immediately after it is followed by a built-in function, and the output variable can be rotated through the built-in function. The following are commonly used built-in string functions:
html: HTML encoding of strings
cap_first: capitalize the first letter of the string
lower_case: convert string to lowercase
upper_case: convert string to uppercase
trim: Remove the whitespace characters before and after the string
Below are the commonly used built-in functions for collections
size: Get the number of elements in the sequence
Below are the commonly used built-in functions for numeric values
int: Get the integer part of the number, the result is signed
For example:
<#assign test="Tom & Jerry">
${test?html}
${test?upper_case?html}
The result is: Tom & Jerry TOM & JERRY
3.10 Null value processing operator
FreeMarker handles null values very strictly. FreeMarker variables must have values. Variables that are not assigned will throw exceptions, because forced errors in FreeMarker's unassigned variables can eliminate many potential errors, such as missing potential variable naming, or other variable errors. The null values mentioned here actually include those variables that do not exist. For a Java null value, we think this variable exists, but its value is null, but for the FreeMarker template, it cannot understand that null value, null value and non-existent variables are exactly the same.
To handle missing variables, FreeMarker provides two operators:
!: Specify the default value of missing variables
??: Determine whether a variable exists
Among them, there are two usages of the ! operator:
variable! or variable!defaultValue, the first usage does not specify a default value for missing variables, indicating that the default value is an empty string, a collection of length 0, or a Map object of length 0.
When specifying the default value, the default value type and variable type are not required to be the same. Using the ?? operator is very simple, it always returns a boolean value, and the usage is: variable??, if the variable exists, it returns true, otherwise it returns false
3.11 Operator priority
The operator priority in FreeMarker is as follows (arranged from high to low):
1, unary operator:!
2. Built-in functions:?
3. Multiplication and division: *, /, %
4. Addition and subtraction:- , +
5. Comparison:> , < , >= , <= (lt , lte , gt , gte)
6, Equal:== , = , !=
7. Logic and:&&
8, Logical or:||
9, Number range:..
In fact, we should use brackets to strictly distinguish them during the development process, so that they have good readability and fewer errors.
4 Common commands for FreeMarker
FreeMarker's FTL instructions are also an important part of the template. These instructions can realize the iteration and branch control of the data contained in the data model. In addition, there are some important functions that are also implemented through FTL instructions.
4.1 if command
This is a typical branch control instruction. The function of this instruction is exactly similar to the syntax format of if and if instruction in Java language is as follows:
<#if condition>...
<#elseif condition>...
<#elseif condition>...
<#else> ...
</#if>
Examples are as follows:
<#assign age=23>
<#if (age>60)>The elderly
<#elseif (age>40)>Mid-aged man
<#elseif (age>20)>Youth People
<#else> teenager
</#if>
The output result is: young people
The logical expressions in the above code are enclosed in parentheses mainly because there are > symbols inside. Since FreeMarker will treat the > symbols as the end character of the label, it may cause errors in the program. In order to avoid this, we should use brackets where these symbols appear.
4.2 switch , case , default , break command
These instructions are obviously branch instructions, and they act like Java switch statements. The syntax structure of switch instructions is as follows:
<#switch value>
<#case refValue>...<#break>
<#case refValue>...<#break>
<#default>...
</#switch>
4.3 list, break command
The list instruction is an iterative output instruction, used to iterate the collection in the output data model. The syntax format of the list instruction is as follows:
<#list sequence as item>
...
</#list>
In the above syntax format, sequence is a collection object or an expression, but the expression will return a collection object, and item is an arbitrary name, which is the collection element output by iterating. In addition, when iterating the collection object, it also contains two special loop variables:
item_index: The index value of the current variable
item_has_next: Whether the next object exists
You can also use the <#break> command to jump out of iteration
Examples are as follows:
<#list ["Monday", "Tuesday", "Thursday", "Friday", "Saturday", "Sunday"] as x>
${x_index + 1}.${x}<#if x_has_next>,</if>
<#if x="Thursday"><#break></#if>
</#list>
4.4 include command
The include directive function is similar to the JSP include directive, and the syntax format of the include directive is used to include the specified page.include directive is as follows:
<#include filename [options]>
In the above syntax format, the two parameters are explained as follows:
filename: This parameter specifies the included template file
options: This parameter can be omitted, specifying the option when inclusion, including two options: encoding and parse. encoding specifies the decoding set used when inclusion pages, and parse specifies whether the included file is parsed as an FTL file. If the parse option value is omitted, the option is true by default.
4.5 import command
This directive is used to import all variables in the FreeMarker template and place the variable in the specified Map object. The syntax format of the import directive is as follows:
<#import "/lib/" as com>
The above code will import all variables in the /lib/ template file, and place these variables in a Map object named com.
4.6 noparse command
The noparse directive specifies that FreeMarker does not process the content contained in the specified. The syntax format of the directive is as follows:
<#noparse>...</#noparse>
See the following example:
<#noparse>
<#list books as book>
<tr><td>${}<td>Author:${}
</#list>
</#noparse>
The output is as follows:
<#list books as book>
<tr><td>${}<td>Author:${}
</#list>
4.7 escape , noescape directive
The escape instruction causes the body area to be interpolated automatically, but it will not affect the interpolation in the string, and will only affect the interpolation in the body. The syntax format of using the escape instruction is as follows:
<#escape identifier as expression>...
<#noescape>...</#noescape>
</#escape>
Look at the following code:
<#escape x as x?html>
First name:${firstName}
Last name:${lastName}
Maiden name:${maidenName}
</#escape>
The above code is equivalent to:
First name:${firstName?html}
Last name:${lastName?html}
Maiden name:${maidenName?html}
The escape directive works when parsing templates instead of when running. In addition, the escape directive is also nested and the child escape inherits the rules of the parent escape, as shown in the following example:
<#escape x as x?html>
Customer Name:${customerName}
Items to ship;
<#escape x as itemCodeToNameMap[x]>
${itemCode1}
${itemCode2}
${itemCode3}
${itemCode4}
</#escape>
</#escape>
The above code is similar to:
Customer Name:${customerName?html}
Items to ship;
${itemCodeToNameMap[itemCode1]?html}
${itemCodeToNameMap[itemCode2]?html}
${itemCodeToNameMap[itemCode3]?html}
${itemCodeToNameMap[itemCode4]?html}
For all interpolations placed in the escape directive, this interpolation will be automatically added with the escape expression. If you need to specify some interpolations in the escape directive without adding escape expressions, you should use the noescape directive. The interpolation placed in the noescape directive will not add the escape expression.
4.8 assign command
The assign directive has been used many times before. It is used to create or replace a top-level variable for the template page. There are many uses of the assign directive, including creating or replacing a top-level variable, or creating or replacing multiple variables, etc. Its simplest syntax is as follows: <#assign name=value [in namespacehash]>, this usage is used to specify a variable named name, and the value of the variable is value. In addition, FreeMarker allows adding an in clause to use the assign directive, and the in clause is used to put the created name variable into the namespacehash namespace.
The assign directive also has the following usage: <#assign name1=value1 name2=value2 ... nameN=valueN [in namespacehash]>, this syntax can create or replace multiple top-level variables at the same time. In addition, there is a complex usage. If the variable value that needs to be created or replaced is a complex expression, the following syntax format can be used: <#assign name [in namespacehash]>capture this</#assign>, in this syntax, it refers to assigning the content of the assign directive to the name variable. The following example:
<#assign x>
<#list ["Monday", "Tuesday", "Thursday", "Friday", "Saturday", "Sunday"] as n>
${n}
</#list>
</#assign>
${x}
The above code will produce the following output: Monday Tuesday Wednesday Thursday Friday Saturday Sunday
Although assign specifies the usage of this complex variable value, we should not abuse this usage, as shown in the following example: <#assign x>Hello ${user}!</#assign>, it is more appropriate to change the above code to the following writing method: <#assign x="Hello ${user}!">
4.9 setting command
This instruction is used to set the FreeMarker running environment. The syntax format of this instruction is as follows: <#setting name=value>. In this format, the value range of name includes the following:
locale: This option specifies the country/language option used by the template
number_format: Specify the format for formatting the output number
boolean_format: Specify the syntax format of two boolean values, the default value is true, false
date_format,time_format,datetime_format: Specify the format for formatting the output date
time_zone: Set the time zone used when formatting the output date
4.10 macro , nested , return command
Macro can be used to implement custom instructions. By using custom instructions, a template fragment can be defined as a user instruction. The syntax format of using macro instructions is as follows:
<#macro name param1 param2 ... paramN>
...
<#nested loopvar1, loopvar2, ..., loopvarN>
...
<#return>
...
</#macro>
In the above format fragment, the following parts are included:
The name:name attribute specifies the name of the custom directive. Multiple parameters can be passed in when using the custom directive.
paramX: This property specifies the use of custom instruction time parameters. When using this custom instruction, values must be passed to these parameters.
nested directive: the middle part of the nested tag output when using custom directives
Loop variable in nested directive: This loop variable will be specified by the macro definition part and passed to the template using the label
return directive: This directive can be used to end the custom directive at any time.
See the following example:
<#macro book> //Define a custom directive
j2ee
</#macro>
<@book /> //Use the commands defined just now
The output result of the above code is: j2ee
In the above code, it may be difficult to see the usefulness of custom tags, because the content contained in the book directive we define is very simple. In fact, custom tags can contain a lot of content, so that better code reuse can be achieved. In addition, when defining custom instructions, you can also specify parameters for custom instructions, see the following code:
<#macro book booklist> //Define a custom directive booklist as a parameter
<#list booklist as book>
${book}
</#list>
</#macro>
<@book booklist=["spring","j2ee"] /> //Use the command you just defined
The above code passes a parameter value for the book instruction, and the output result of the above code is: spring j2ee
Not only that, you can also use nested directives to output the middle part of the custom instruction when customizing the instruction, see the following example:
<#macro page title>
<html>
<head>
<title>FreeMarker sample page - ${title?html}</title>
</head>
<body>
<h1>${title?html}</h1>
<#nested> //Tag body used to introduce user-defined instructions
</body>
</html>
</#macro>
The above code defines an HTML page template as a page directive, so the page directive can be used in other pages:
<#import "/" as com> //Suppose the above template page is named, import the page
<@ title="book list">
<u1>
<li>spring</li>
<li>j2ee</li>
</ul>
</@>
As can be seen from the above example, using macro and nested instructions can easily achieve page decoration effect. In addition, you can also specify one or more loop variables when using nested instructions, see the following code:
<#macro book>
<#nested 1> //A loop variable value is specified when using the book instruction
<#nested 2>
</#macro>
<@book ;x> ${x} .Book</@book>
When passing in variable values using nested directives, when using the custom directive, you need to use a placeholder (such as after the book directive; x). The above code output text is as follows:
1. Books 2. Books
When using loop variables in nested directives, multiple loop variables can be used, see the following code:
<#macro repeat count>
<#list 1..count as x> //Three loop variables are specified when using nested directive
<#nested x, x/2, x==count>
</#list>
</#macro>
<@repeat count=4 ; c halfc last>
${c}. ${halfc}<#if last> Last! </#if>
</@repeat>
The above output is:
1. 0.5 2. 1 3. 1.5 4. 2 Last;
The return instruction is used to end the macro instruction. Once the return instruction is executed in the macro instruction, FreeMarker will not continue to process the contents in the macro instruction. See the following code:
<#macro book>
spring
<#return>
j2ee
</#macro>
<@book />
The above code outputs: spring, and j2ee is located after the return instruction and will not output.
if, else, elseif
switch, case, default, break
list, break
include
Import
compress
escape, noescape
assign
global
setting
macro, nested, return
t, lt, rt
3 Some common methods or precautions
Expression conversion class
Digital loop
Take integers for floating point
Give the default value of the variable
Determine whether the object is null
Common formatting dates
Add global shared variable data model
Directly calling java object methods
String processing (built-in method)
Initialize sequences and hashes in the template
Comment flag
Built-in sequences method
Hashes built-in method
4 Things to note in freemarker in web development
Several commonly used objects in the web
Search order of values in view
Use tags in ftl in template
How to initialize shared variables
Integrate configuration with webwork
5 Advanced Methods
Custom Method
Custom Transforms
1 concept
The 3 most commonly used concepts
sequence sequence, corresponding to a collection of non-key-value pairs such as list, array, etc. in java
hash Collection of key-value pairs
namespace is a reference to an ftl file. This name allows you to access the resources of the ftl file.
2 commands
if, else, elseif
grammar
<#if condition>
...
<#elseif condition2>
...
<#elseif condition3>
...
...
<#else>
...
</#if>
Use Cases
<#if x = 1>
x is 1
</#if>
<#if x = 1>
x is 1
<#else>
x is not 1
</#if>
switch, case, default, break
grammar
<#switch value>
<#case refValue1>
...
<#break>
<#case refValue2>
...
<#break>
...
<#case refValueN>
...
<#break>
<#default>
...
</#switch>
Use Cases
String
<#switch >
<#case "small">
This will be processed if it is small
<#break>
<#case "medium">
This will be processed if it is medium
<#break>
<#case "large">
This will be processed if it is large
<#break>
<#default>
This will be processed if it is neither
</#switch>
number
<#switch x>
<#case x = 1>
1
<#case x = 2>
2
<#default>
d
</#switch>
If x=1 output 1 2, x=2 output 2, x=3 output d
list, break
grammar
<#list sequence as item>
...
<#if item = "spring"><#break></#if>
...
</#list>
Keywords
item_index: is the subscript of the current value of the list
item_has_next: determine whether the list still has a value
Use Cases
<#assign seq = ["winter", "spring", "summer", "autumn"]>
<#list seq as x>
${x_index + 1}. ${x}<#if x_has_next>,</#if>
</#list>
Output
1. winter,
2. spring,
3. summer,
4. autumn
include
grammar
<#include filename>
or
<#include filename options>
options contain two properties
encoding=”GBK” encoding format
Whether parse=true is parsed as ftl syntax, default is true, false is introduced in text. Note that in the ftl file, Boolean values are directly assigned, such as parse=true, rather than parse=”true”
Use Cases
/common/Includes content
Copyright 2001-2002 ${me}<br>
All rights reserved.
Template file
<#assign me = "Juila Smith">
<h1>Some test</h1>
<p>Yeah.
<hr>
<#include "/common/" encoding=”GBK”>
Output result
<h1>Some test</h1>
<p>Yeah.
<hr>
Copyright 2001-2002 Juila Smith
All rights reserved.
Import
grammar
<#import path as hash>
Similar to the import in java, it imports the file, and then you can use the macro components that are imported into the file in the current file.
Use Cases
Assuming that the macro copyright is defined, we can use it in other template pages.
<#import "/libs/" as my>
<@ date="1999-2002"/>
"my" is called namespace in freemarker
compress
grammar
<#compress>
...
</#compress>
Used to compress empty space and blank lines
Use Cases
<#assign x = " moo \n\n ">
(<#compress>
1 2 3 4 5
${moo}
test only
I said, test only
</#compress>)
Output
(1 2 3 4 5
moo
test only
I said, test only)
escape, noescape
grammar
<#escape identifier as expression>
...
<#noescape>...</#noescape>
...
</#escape>
Use Cases
It mainly uses similar string variable outputs. For example, all string outputs of a certain module must be html-safe. This expression can be used at this time.
<#escape x as x?html>
First name: ${firstName}
<#noescape>Last name: ${lastName}</#noescape>
Maiden name: ${maidenName}
</#escape>
Same expression
First name: ${firstName?html}
Last name: ${lastName }
Maiden name: ${maidenName?html}
assign
grammar
<#assign name=value>
or
<#assign name1=value1 name2=value2 ... nameN=valueN>
or
<#assign same as above... in namespacehash>
or
<#assign name>
capture this
</#assign>
or
<#assign name in namespacehash>
capture this
</#assign>
Use Cases
Generate variables and assign values to the variables
Assign sequence values to seasons
<#assign seasons = ["winter", "spring", "summer", "autumn"]>
Add 1 to the variable test
<#assign test = test + 1>
Assign a variable bgColor to my namepage, you can access this variable below
<#import "/" as my>
<#assign bgColor="red" in my>
Save a piece of output text as a variable in x
The text output in the shadowed part below will be assigned to x
<#assign x>
<#list 1..3 as n>
${n} <@myMacro />
</#list>
</#assign>
Number of words: ${x?word_list?size}
${x}
<#assign x>Hello ${user}!</#assign> error
<#assign x=” Hello ${user}!”> true
It also supports Chinese assignment, such as:
<#assign syntax>
java
</#assign>
${Syntax}
Printout:
java
global
grammar
<#global name=value>
or
<#global name1=value1 name2=value2 ... nameN=valueN>
or
<#global name>
capture this
</#global>
Global assignment syntax, using this syntax to assign values to a variable, then this variable is visible in all namespaces. If this variable is overwritten by the current assign syntax, such as <#global x=2> <#assign x=1> In the current page, x=2 will be hidden, or accessed through ${.}
setting
grammar
<#setting name=value>
Used to set up an environment for the entire system
locale
number_format
boolean_format
date_format, time_format, datetime_format
time_zone
classic_compatible
Use Cases
If the current setting is Hungarian, then modify it to the United States
${1.2}
<#setting locale="en_US">
${1.2}
Output
1,2
1.2
Because Hungary uses "," as the decimal separator, the United States uses "."
macro, nested, return
grammar
<#macro name param1 param2 ... paramN>
...
<#nested loopvar1, loopvar2, ..., loopvarN>
...
<#return>
...
</#macro>
Use Cases
<#macro test foo bar="Bar" baaz=-1>
Test text, and the params: ${foo}, ${bar}, ${baaz}
</#macro>
<@test foo="a" bar="b" baaz=5*5-2/>
<@test foo="a" bar="b"/>
<@test foo="a" baaz=5*5-2/>
<@test foo="a"/>
Output
Test text, and the params: a, b, 23
Test text, and the params: a, b, -1
Test text, and the params: a, Bar, 23
Test text, and the params: a, Bar, -1
Define the macro that loops out
<#macro list title items>
<p>${title?cap_first}:
<ul>
<#list items as x>
<li>${x?cap_first}
</#list>
</ul>
</#macro>
<@list items=["mouse", "elephant", "python"] title="Animals"/>
Output result
<p>Animals:
<ul>
<li>Mouse
<li>Elephant
<li>Python
</ul>
Macros containing body
<#macro repeat count>
<#list 1..count as x>
<#nested x, x/2, x==count>
</#list>
</#macro>
<@repeat count=4 ; c halfc last>
${c}. ${halfc}<#if last> Last!</#if>
</@repeat>
Output
1. 0.5
2. 1
3. 1.5
4. 2 Last!
t, lt, rt
grammar
<#t> Remove left and right blanks and enter to wrap
<#lt>Remove the blank on the left and enter the car and line
<#rt>Remove the blank on the right and enter the car and line
<#nt>Cancel the above effect
3 Some common methods or precautions
Expression conversion class
${expression} calculates expression and outputs
#{ expression }numeric calculation#{ expression ;format}In the format output numeric format is M and m
M represents the number of digits after the decimal point, m represents the number of digits after the decimal point, such as #{121.2322;m2M2} output 121.23
Digital loop
1..5 means from 1 to 5, prototype number..number
Take integers for floating point
${123.23?int} Output 123
Give the default value of the variable
${var?default("hello world<br>")?html}If var is null, it will be replaced by hello world<br>
Determine whether the object is null
<#if mouse?exists>
Mouse found
<#else>
You can also directly output a boolean shape by ${mouse?if_exists})
Common formatting dates
OpeningTime must be Date type, please view the freemarker document in detail Reference->build-in reference->build-in for date
${openingTime?date}
${openingTime?date_time}
${openingTime?time}
Add global shared variable data model
Implementation in code
cfg = ();
("global", "you good");
The page implementation can be done through the global command to view the global part in the command in detail.
Directly calling java object methods
${(args)}
String processing (built-in method)
html safe output
“abc<table>sdfsf”?html
Return safe html output, replace html code
xml safe output
var?xml
Usage of substring
<#assign user=”hello jeen”>
${user[0]}${user[4]}
${user[1..4]}
Output:
ho
ello
Similar usage
"abc;def;ghi"?split(";") returns sequence
Convert the string into sequence by space, and then take the length of the sequence
var?word_list The effect is the same as var?split(" )
var?word_list?size
Get string length
var?length
Caps output characters
var?upper_case
Lowercase output characters
var?lower_case
First character capitalization
var?cap_first
Lowercase first character
var?uncap_first
Remove the spaces before and after the string
var?trim
Capitalize the first character of each word
var?capitalize
similar:
"babcdabcd"?index_of("abc") Return 1
"babcdabcd"?index_of("abc",2) Return 5
similar
last_index_of and similar, same as above
The following two may be used when generating code (add "\" before quotation marks)
j_string: add "\" before string quotation marks
<#assign beanName = 'The "foo" bean.'>
String BEAN_NAME = "${beanName?j_string}";
Printout:
String BEAN_NAME = "The \"foo\" bean.";
js_string:
<#assign user = "Big Joe's \"right hand\".">
<script>
alert("Welcome ${user}!");
</script>
Print Out
alert("Welcome Big Joe\'s \"right hand\"!");
Replace string replace
${s?replace(‘ba’, ‘XY’ )}
${s?replace('ba', 'XY', 'rule parameters')} Replace all ba in s with xy Rule parameters include: i r m s c f The specific meaning is as follows:
· i: Indistinguishable from upper and lower case.
· f: Replace only the first string with the replaced string
· r: XY is a regular expression
· m: Multi-line mode for regular expressions. In multi-line mode the expressions ^ and $ match just after or just before, respectively, a line terminator or the end of the string. By default these expressions only match at the beginning and the end of the entire string.
· s: Enables dotall mode for regular expressions (same as Perl singe-line mode). In dotall mode, the expression . matches any character, including a line terminator. By default this expression does not match line terminators.
· c: Permits whitespace and comments in regular expressions.
Initialize sequences and hashes in the template
sequences
1. [“you”,”me”,”he”]
2. 1..100
3. [ {“Akey”:”Avalue”},{“Akey1”:”Avalue1”},
{“Bkey”:”Bvalue”},{“Bkey1”:”Bvalue1”},
]
hashes {“you”:”a”,”me”:”b”,”he”:”c”}
Comment flag
<#--
Here is the comment
-->
The old version of freemarker uses the <#comment> comment </#comment> method
Built-in sequences method
sequence?first
Returns the first value of sequence; prerequisite sequence cannot be null
sequence?last
Return the last value of sequence
sequence?reverse
Reverse the value of sequence
sequence?size
Returns the size of sequence
sequence?sort
Sort sequence by the result of the object toString() inside
sequence?sort_by(value)
Sort sequence by the attribute value of the object inside
For example: The sequence contains 10 user objects, and the user object contains attributes such as name, age, etc.
sequence?sort_by(name) means that all users are sorted by
Hashes built-in method
hash?keys
Return all keys in hash, return result type sequence
hash?values
Return all values in hash, return result type sequence
4 Things to note in freemarker in web development
Freemarker and webwork integration
Several commonly used objects in the web
Use internal objects directly in the ftl file of Freemarker:
${Request ["a"]}
${RequestParameters["a"]}
${Session ["a"]}
${Application ["a"]}
${JspTaglibs ["a"]}
After integration with webwork, the configured servlet has been placed in the data model.
The following object exists in the view
We can print the req object in ftl ${req}
· req - the current HttpServletRequest
· res - the current HttpServletResponse
· stack - the current OgnlValueStack
· ognl - the OgnlTool instance
· webwork - an instance of FreemarkerWebWorkUtil
· action - the current WebWork action
· exception - optional the Exception instance, if the view is a JSP exception or Servlet exception view
Search order of values in view
${name} will look for name values in the following order
· freemarker variables
· value stack
· request attributes
· session attributes
· servlet context attributes
Use tags in ftl in template
Note that if the attribute value of the label is a number, then the attribute must be assigned to the value using the nubmer=123 method.
JSP page
<%@page contentType="text/html;charset=ISO-8859-2" language="java"%>
<%@taglib uri="/WEB-INF/" prefix="html"%>
<%@taglib uri="/WEB-INF/" prefix="bean"%>
<html>
<body>
<h1><bean:message key=""/></h1>
<html:errors/>
<html:form action="/query">
Keyword: <html:text property="keyword"/><br>
Exclude: <html:text property="exclude"/><br>
<html:submit value="Send"/>
</html:form>
</body>
</html>
Template ftl page
<#assign html=JspTaglibs["/WEB-INF/"]>
<#assign bean=JspTaglibs["/WEB-INF/"]>
<html>
<body>
<h1><@ key=""/></h1>
<@/>
<@ action="/query">
Keyword: <@ property="keyword"/><br>
Exclude: <@ property="exclude"/><br>
<@ value="Send"/>
</@>
</body>
</html>
How to initialize shared variables
1. Initialize the global shared data model
When freemark is used on the web, it does not support the initialization of shared data. It cannot be implemented during configuration initialization, but must be initialized through the ftl file. This cannot meet the main needs. We need to leave an interface when servlet init to initialize the shared data of the system
Specifically, it is integrated with webwork, because webwork itself provides integrated servlets. If you want to add global shared variables, you can implement them by modifying them. We can initialize global shared variables when this servlet is initialized.
Integrate configuration with webwork
Configuration
<servlet>
<servlet-name>freemarker</servlet-name>
<servlet-class></servlet-class>
<init-param>
<param-name>TemplatePath</param-name>
<param-value>/</param-value>
<!—Template loads the folder, here, relative to context root, recursively obtains all templates under the folder -->
</init-param>
<init-param>
<param-name>NoCache</param-name> <!—Whether to cache templates-->
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>ContentType</param-name>
<param-value>text/html</param-value>
</init-param>
<init-param>
<param-name>template_update_delay</param-name>
<!—Template update time, 0 means update every time, this is suitable for development time-->
<param-value>0</param-value>
</init-param>
<init-param>
<param-name>default_encoding</param-name>
<param-value>GBK</param-value>
</init-param>
<init-param>
<param-name>number_format</param-name>
<param-value>0.###########</param-value><!—Digital display format-->
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>freemarker</servlet-name>
<url-pattern>*.ftl</url-pattern>
</servlet-mapping>
5 Advanced Methods
Custom Method
${timer("yyyy-MM-dd H:mm:ss", x)}
${timer("yyyy-MM-dd ", x)}
In the template, in addition to calling methods through objects (${(args)}), you can also directly call methods implemented by java. The java class must implement the method of the interface TemplateMethodModel exec(List args). The following is an example of converting the millisecond time into the time output in the format as a sample.
public class LongToDate implements TemplateMethodModel {
public TemplateModel exec(List args) throws TemplateModelException {
SimpleDateFormat mydate = new SimpleDateFormat((String) (0)));
return (new Date(((String)(1)));
}
}
Put the LongToDate object into the data model
("timer", new IndexOfMethod());
Used in ftl template
<#assign x = "123112455445">
${timer("yyyy-MM-dd H:mm:ss", x)}
${timer("yyyy-MM-dd ", x)}
Output
2001-10-12 5:21:12
2001-10-12
Custom Transforms
Implement the function of custom <@transform> text or expression</@transform>, allowing parsing and conversion of the middle final text
Example: Implement the function of converting str into STR
The code is as follows:
import .*;
import .*;
import ;
class UpperCaseTransform implements TemplateTransformModel {
public Writer getWriter(Writer out, Map args) {
return new UpperCaseWriter(out);
}
private class UpperCaseWriter extends Writer {
private Writer out;
UpperCaseWriter (Writer out) {
= out;
}
public void write(char[] cbuf, int off, int len)
throws IOException {
(new String(cbuf, off, len).toUpperCase());
}
public void flush() throws IOException {
();
}
public void close() {
}
}
}
Then put this object into the data model
("upcase", new UpperCaseTransform());
In the view(ftl) page, you can use it as follows
<@upcase>
hello world
</@upcase>
Printout:
HELLO WORLD
All the following contents are collected online:
FreeMarker's template file is not much more complicated than HTML pages. FreeMarker template file is mainly composed of the following 4 parts:
1. Text: the direct output part
2. Comment: <#-- ... --> format part, will not output
3. Interpolation: i.e. the part of the format ${...} or #{...} will be used instead of the output in the data model.
4. FTL instruction: FreeMarker is specified, similar to HTML tags, and the name is added to distinguish it, and it will not be output.
Below is an example of the FreeMarker template, including the 4 parts mentioned above
<html><br>
<head><br>
<title>Welcome!</title><br>
</head><br>
<body><br>
<#-- Comments section --><br>
<#-- Use interpolation below -->
<h1>Welcome ${user} !</h1><br>
<p>We have these animals:<br>
<u1><br>
<#-- Use FTL instruction -->
<#list animals as being><br>
<li>${} for ${} Euros<br>
<#list><br>
<u1><br>
</body><br>
</html>
1. FTL instruction rules
In FreeMarker, using FTL tags to use instructions. FreeMarker has 3 types of FTL tags, which are exactly similar to HTML tags.
1. Start tag: <#directivename parameter>
2. End tag:</#directivename>
3. Empty tag:<#directivename parameter/>
In fact, the previous symbol # when using the tag may also become @. If the instruction is a user instruction rather than a built-in instruction in the system, the # symbol should be changed to the @ symbol.
When using FTL tags, there should be correct nesting instead of cross-using, which is exactly the same as XML tag usage. If you use non-existent directives, FreeMarker will not use the template output, but will generate an error message. FreeMarker will ignore whitespace characters in the FTL tag. It is worth noting that whitespace characters are not allowed between < , /> and directives.
2. Interpolation rules
FreeMarker interpolation has the following two types: 1, general interpolation ${expr}; 2, digital format interpolation: #{expr} or #{expr;format}
2.1 General Interpolation
For general interpolation, it can be divided into the following 4 situations:
1. The interpolation result is a string value: Direct output expression result
2. The interpolation result is a numeric value: convert the expression result into text output according to the default format (setting by the #setting directive). Single interpolation can be formatted using the built-in string function, as shown in the following example:
<#settion number_format="currency"/>
<#assign answer=42/>
${answer}
${answer?string} <#-- the same as ${answer} -->
${answer?}
${answer?}
${answer?}
${answer}
The output result is:
$42.00
$42.00
42
$42.00
4,200%
3. The interpolation result is a date value: convert the expression result into text output according to the default format (setting by the #setting directive). Single interpolation can be formatted using the built-in string function, as shown in the following example:
${lastUpdated?string("yyyy-MM-dd HH:mm:ss zzzz")}
${lastUpdated?string("EEE, MMM d, ''yy")}
${lastUpdated?string("EEEE, MMMM dd, yyyy, hh:mm:ss a '('zzz')'")}
The output result is:
2008-04-08 08:08:08 Pacific Daylight Time
Tue, Apr 8, '03
Tuesday, April 08, 2003, 08:08:08 PM (PDT)
4. The interpolation result is a boolean value: convert the expression result into text output according to the default format (setting by the #setting directive). Single interpolation can be formatted using the built-in string function, as shown in the following example:
<#assign foo=true/>
${foo?string("yes", "no")}
The output result is:
yes
2.2 Digital formatting interpolation
Number format interpolation can be used in the form of #{expr;format} to format numbers, where format can be:
mX: The smallest X digit of the fractional part
MX: The maximum X digit of the decimal part
As in the following example:
<#assign x=2.582/>
<#assign y=4/>
#{x; M2} <#- Output 2.58 -->
#{y; M2} <#- Output 4 -->
#{x; m2} <#- Output 2.6 -->
#{y; m2} <#- Output 4.0 -->
#{x; m1M2} <#- Output 2.58 -->
#{x; m1M2} <#- Output 4.0 -->
3. Expressions
Expressions are the core function of the FreeMarker template. When an expression is placed in the interpolation syntax ${}, it indicates that the value of the expression needs to be output; the expression syntax can also be combined with the FreeMarker tag to control the output. In fact, FreeMarker's expression function is very powerful. It not only supports direct specifying values and outputting variable values, but also supports string formatted output and collection access.
3.1 Specify the value directly
Use the direct value specifying syntax to let FreeMarker output the values in the interpolated value directly, rather than outputting variable values. The direct value specified can be strings, numeric values, boolean values, collections, and MAP objects.
1, string
Directly specifying the string value is limited by single or double quotes. If the string value contains special characters and needs to be escaped, see the following example:
${"My file is saved in C:\\Disk"}
${'My name is \"annlee\"'}
The output result is:
My file is saved in C:\disk
My name is "annlee"
FreeMarker supports the following escape characters:
\";Double quotes (u0022)
\';Single quotes (u0027)
\\;Backslash(u005C)
\n;Line Break(u000A)
\r;Enter(u000D)
\t;Tab(u0009)
\b;Backspace key (u0008)
\f;Form feed(u000C)
\l;<
\g;>
\a;&
\{;{
\xCode; directly specify the Unicode code through a 4-digit hexadecimal number, and output the characters corresponding to the unicode code.
If a paragraph of text contains a large number of special symbols, FreeMarker provides another special format: you can add r marks before the quotation marks of the specified string content, and the file after the r mark will be directly output. See the following code:
${r"${foo}"}
${r"C:\foo\bar"}
The output result is:
${foo}
C:\foo\bar
2, value
The values in the expression are output directly without quotation marks. The decimal points are separated by ".", and groupings cannot be used. FreeMarker does not currently support scientific notation, so "1E3" is wrong. You need to pay attention to the following points when using numeric values in FreeMarker expressions:
1. The 0 before the decimal point cannot be omitted, so ".5" is the wrong way to write it
2, the values 8, +8, 8.00 are all the same
3, boolean value
Use true and false directly, without quotes.
4, collection
The set is included in square brackets, and the elements of each set are separated by English commas "," as shown in the following example:
<#list ["Monday", "Tuesday", "Thursday", "Friday", "Saturday", "Sunday"] as x>
${x}
</#list>
The output result is:
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
In addition, collection elements can also be expressions, examples are as follows:
[2 + 2, [1, 2, 3, 4], "whatnot"]
You can also use numeric ranges to define numeric sets, such as 2..5 is equivalent to [2, 3, 4, 5], but it is more efficient. Note that when using numeric ranges to define sets, there is no need to use square brackets, and numeric ranges also support inverse incremental numeric ranges, such as 5..2
5. Map object
Map objects use curly braces to include, the key-value pairs in the Map are separated by the English colon:" and the multiple sets of key-value pairs are separated by the English comma" and ". The following is an example:
{"Chinese":78, "Mathematics":80}
The key and value of the Map object are both expressions, but the key must be a string
3.2 Output variable value
When FreeMarker's expression outputs variables, these variables can be top-level variables, variables in Map objects, variables in sets, and can use point (.) syntax to access the properties of Java objects. These situations are discussed below.
1. Top variable
The so-called top-level variable is the value placed directly in the data model, for example, there is the following data model:
Map root = new HashMap(); //Create a data model
("name","annlee"); //name is a top-level variable
For top-level variables, use ${variableName} directly to output the variable value. The variable name can only be a combination of letters, numbers, underscores, $, @ and #, and cannot start with numbers. In order to output the value of the above name, the following syntax can be used:
${name}
2. Output collection elements
If you need to output a collection element, you can output the collection element according to the index of the collection element, and the index of the collection element is specified in square brackets. Suppose there is an index:
["Monday", "Tuesday", "Thursday", "Friday", "Saturday", "Sunday"]. The index is called week. If you need to output Wednesday, you can use the following syntax:
${week[2]} //Output the third collection element
In addition, FreeMarker also supports returning subsets of collections. If you need to return subsets of collections, you can use the following syntax:
week[3..5] //Returns a subset of the week set, the elements in the subset are the 4th to 6th elements in the week set
3. Output Map elements
The Map object here can be a direct HashMap instance, or even a JavaBean instance. For JavaBean instances, we can also regard it as a Map instance with a property key and an attribute value. In order to output the value of the Map element, you can use dot syntax or square bracket syntax. If there is the following data model:
Map root = new HashMap();
Book book = new Book();
Author author = new Author();
("annlee");
("gz");
("struts2");
(author);
("info","struts");
("book", book);
To access the name of the author of the book named struts2 in the data model, the following syntax can be used:
//Use all dot syntax
book["author"].name
["name"] //Mixed point syntax and square bracket syntax
book["author"]["name"] //Everything uses square bracket syntax
When using dot syntax, variable names have the same limitation as top-level variables, but square bracket syntax does not have this limitation because the name can be the result of any expression.
3.3, String operation
FreeMarker's expressions are very flexible in string operations, and can concatenate string constants and variables, or return substrings of strings, etc.
There are two syntaxes for string concatenation:
1. Use ${..} or #{..} to insert the value of the expression in the constant part of the string to complete the string concatenation.
2. Directly use the connection operator + to connect the string
For example, there is the following data model:
Map root = new HashMap(); ("user","annlee");
The following links the user variable and the constant:
${"hello, ${user}!"} //Use the first syntax to connect
${"hello, " + user + "!"} //Use the + sign to connect
The output strings above are all hello, annlee!, and it can be seen that the effects of these two syntaxes are exactly the same.
It is worth noting that ${..} can only be used for text parts and cannot be used for expressions. The following code is wrong:
<#if ${isBig}>Wow!</#if>
<#if "${isBig}">Wow!</#if>
It should be written as: <#if isBig>Wow!</#if>
Intercepting substrings can be performed based on the index of the string. When intercepting substrings, if only one index value is specified, it is used to obtain the characters corresponding to the specified index in the string; if two index values are specified, the string substring between the two indexes is returned. If there is the following data model:
Map root = new HashMap(); ("book","struts2,freemarker");
Substrings can be intercepted by the following syntax:
${book[0]}${book[4]} //The result is su
${book[1..4]} //The result is true
3.4 Collection connection operator
The set operator mentioned here is to connect two sets into a new set. The operator connecting the set is +, see the following example:
<#list ["Monday","Tuesday","Wednesday"] + ["Thursday","Friday","Saturday"] as x>
${x}
</#list>
The output is: Monday Tuesday Wednesday Thursday Friday Saturday Sunday
3.5 Map connection operator
The connection operator of the Map object also connects two Map objects into a new Map object. The connection operator of the Map object is +. If the two Map objects have the same key, the value on the right replaces the value on the left. See the following example:
<#assign scores = {"Chinese":86,"Mathematics":78} + {"Mathematics":87,"Java":93}>
Chinese score is ${scores.Chinese}
Mathematics score is ${scores.Mathematics}
Java score is ${}
The output result is:
Chinese score is 86
Mathematics score is 87
Java score is 93
3.6 Arithmetic operators
FreeMarker expression fully supports arithmetic operations. FreeMarker supports arithmetic operators: +, -, *, /, % See the following code:
<#assign x=5>
${ x * x - 100 }
${ x /2 }
${ 12 %10 }
The output result is:
-75 2.5 2
The following points should be paid attention to when using arithmetic operators in expressions:
1. The number of the operator on both sides must be a number
2. When using the + operator, if one side is a number and the other side is a string, the number will be automatically converted into a string and then connected, such as: ${3 + "5"}, the result is: 35
Use the built-in int function to round the numerical value, such as:
<#assign x=5>
${ (x/2)?int }
${ 1.1?int }
${ 1.999?int }
${ -1.1?int }
${ -1.999?int }
The result is: 2 1 1 -1 -1
3.7 Comparison operators
There are several comparison operators supported in expressions:
1,=or==: determine whether the two values are equal.
2,!=: Determine whether the two values are not equal.
3,>or gt: determine whether the left value is greater than the right value
4,>= or gte: determine whether the left value is greater than or equal to the right value
5,<or lt: determine whether the left value is smaller than the right value
6, <= or lte: determine whether the left value is less than or equal to the right value
Note: = and != can be used to compare whether the values and dates are equal, but the sides of = and != must be of the same type of value, otherwise an error will occur. Moreover, FreeMarker is an exact comparison, "x", "x", "X" are not equal. Other runners can act on numbers and dates, but cannot act on strings. Most of the time, using letter operators such as gt instead of > will have a better effect, because FreeMarker will interpret > as the end character of the FTL tag. Of course, brackets can also be used to avoid this situation, such as: <#if (x>y)>
3.8 Logical operators
There are several logical operators:
Logic and :&&
Logical or:||
Logical non:!
Logical operators can only act on boolean values, otherwise an error will be generated
3.9 Built-in functions
FreeMarker also provides some built-in functions to convert output, which can be followed by any variable immediately after it is followed by a built-in function, and the output variable can be rotated through the built-in function. The following are commonly used built-in string functions:
html: HTML encoding of strings
cap_first: capitalize the first letter of the string
lower_case: convert string to lowercase
upper_case: convert string to uppercase
trim: Remove the whitespace characters before and after the string
Below are the commonly used built-in functions for collections
size: Get the number of elements in the sequence
Below are the commonly used built-in functions for numeric values
int: Get the integer part of the number, the result is signed
For example:
<#assign test="Tom & Jerry">
${test?html}
${test?upper_case?html}
The result is: Tom & Jerry TOM & JERRY
3.10 Null value processing operator
FreeMarker handles null values very strictly. FreeMarker variables must have values. Variables that are not assigned will throw exceptions, because forced errors in FreeMarker's unassigned variables can eliminate many potential errors, such as missing potential variable naming, or other variable errors. The null values mentioned here actually include those variables that do not exist. For a Java null value, we think this variable exists, but its value is null, but for the FreeMarker template, it cannot understand that null value, null value and non-existent variables are exactly the same.
To handle missing variables, FreeMarker provides two operators:
!: Specify the default value of missing variables
??: Determine whether a variable exists
Among them, there are two usages of the ! operator:
variable! or variable!defaultValue, the first usage does not specify a default value for missing variables, indicating that the default value is an empty string, a collection of length 0, or a Map object of length 0.
When specifying the default value, the default value type and variable type are not required to be the same. Using the ?? operator is very simple, it always returns a boolean value, and the usage is: variable??, if the variable exists, it returns true, otherwise it returns false
3.11 Operator priority
The operator priority in FreeMarker is as follows (arranged from high to low):
1, unary operator:!
2. Built-in functions:?
3. Multiplication and division: *, /, %
4. Addition and subtraction:- , +
5. Comparison:> , < , >= , <= (lt , lte , gt , gte)
6, Equal:== , = , !=
7. Logic and:&&
8, Logical or:||
9, Number range:..
In fact, we should use brackets to strictly distinguish them during the development process, so that they have good readability and fewer errors.
4 Common commands for FreeMarker
FreeMarker's FTL instructions are also an important part of the template. These instructions can realize the iteration and branch control of the data contained in the data model. In addition, there are some important functions that are also implemented through FTL instructions.
4.1 if command
This is a typical branch control instruction. The function of this instruction is exactly similar to the syntax format of if and if instruction in Java language is as follows:
<#if condition>...
<#elseif condition>...
<#elseif condition>...
<#else> ...
</#if>
Examples are as follows:
<#assign age=23>
<#if (age>60)>The elderly
<#elseif (age>40)>Mid-aged man
<#elseif (age>20)>Youth People
<#else> teenager
</#if>
The output result is: young people
The logical expressions in the above code are enclosed in parentheses mainly because there are > symbols inside. Since FreeMarker will treat the > symbols as the end character of the label, it may cause errors in the program. In order to avoid this, we should use brackets where these symbols appear.
4.2 switch , case , default , break command
These instructions are obviously branch instructions, and they act like Java switch statements. The syntax structure of switch instructions is as follows:
<#switch value>
<#case refValue>...<#break>
<#case refValue>...<#break>
<#default>...
</#switch>
4.3 list, break command
The list instruction is an iterative output instruction, used to iterate the collection in the output data model. The syntax format of the list instruction is as follows:
<#list sequence as item>
...
</#list>
In the above syntax format, sequence is a collection object or an expression, but the expression will return a collection object, and item is an arbitrary name, which is the collection element output by iterating. In addition, when iterating the collection object, it also contains two special loop variables:
item_index: The index value of the current variable
item_has_next: Whether the next object exists
You can also use the <#break> command to jump out of iteration
Examples are as follows:
<#list ["Monday", "Tuesday", "Thursday", "Friday", "Saturday", "Sunday"] as x>
${x_index + 1}.${x}<#if x_has_next>,</if>
<#if x="Thursday"><#break></#if>
</#list>
4.4 include command
The include directive function is similar to the JSP include directive, and the syntax format of the include directive is used to include the specified page.include directive is as follows:
<#include filename [options]>
In the above syntax format, the two parameters are explained as follows:
filename: This parameter specifies the included template file
options: This parameter can be omitted, specifying the option when inclusion, including two options: encoding and parse. encoding specifies the decoding set used when inclusion pages, and parse specifies whether the included file is parsed as an FTL file. If the parse option value is omitted, the option is true by default.
4.5 import command
This directive is used to import all variables in the FreeMarker template and place the variable in the specified Map object. The syntax format of the import directive is as follows:
<#import "/lib/" as com>
The above code will import all variables in the /lib/ template file, and place these variables in a Map object named com.
4.6 noparse command
The noparse directive specifies that FreeMarker does not process the content contained in the specified. The syntax format of the directive is as follows:
<#noparse>...</#noparse>
See the following example:
<#noparse>
<#list books as book>
<tr><td>${}<td>Author:${}
</#list>
</#noparse>
The output is as follows:
<#list books as book>
<tr><td>${}<td>Author:${}
</#list>
4.7 escape , noescape directive
The escape instruction causes the body area to be interpolated automatically, but it will not affect the interpolation in the string, and will only affect the interpolation in the body. The syntax format of using the escape instruction is as follows:
<#escape identifier as expression>...
<#noescape>...</#noescape>
</#escape>
Look at the following code:
<#escape x as x?html>
First name:${firstName}
Last name:${lastName}
Maiden name:${maidenName}
</#escape>
The above code is equivalent to:
First name:${firstName?html}
Last name:${lastName?html}
Maiden name:${maidenName?html}
The escape directive works when parsing templates instead of when running. In addition, the escape directive is also nested and the child escape inherits the rules of the parent escape, as shown in the following example:
<#escape x as x?html>
Customer Name:${customerName}
Items to ship;
<#escape x as itemCodeToNameMap[x]>
${itemCode1}
${itemCode2}
${itemCode3}
${itemCode4}
</#escape>
</#escape>
The above code is similar to:
Customer Name:${customerName?html}
Items to ship;
${itemCodeToNameMap[itemCode1]?html}
${itemCodeToNameMap[itemCode2]?html}
${itemCodeToNameMap[itemCode3]?html}
${itemCodeToNameMap[itemCode4]?html}
For all interpolations placed in the escape directive, this interpolation will be automatically added with the escape expression. If you need to specify some interpolations in the escape directive without adding escape expressions, you should use the noescape directive. The interpolation placed in the noescape directive will not add the escape expression.
4.8 assign command
The assign directive has been used many times before. It is used to create or replace a top-level variable for the template page. There are many uses of the assign directive, including creating or replacing a top-level variable, or creating or replacing multiple variables, etc. Its simplest syntax is as follows: <#assign name=value [in namespacehash]>, this usage is used to specify a variable named name, and the value of the variable is value. In addition, FreeMarker allows adding an in clause to use the assign directive, and the in clause is used to put the created name variable into the namespacehash namespace.
The assign directive also has the following usage: <#assign name1=value1 name2=value2 ... nameN=valueN [in namespacehash]>, this syntax can create or replace multiple top-level variables at the same time. In addition, there is a complex usage. If the variable value that needs to be created or replaced is a complex expression, the following syntax format can be used: <#assign name [in namespacehash]>capture this</#assign>, in this syntax, it refers to assigning the content of the assign directive to the name variable. The following example:
<#assign x>
<#list ["Monday", "Tuesday", "Thursday", "Friday", "Saturday", "Sunday"] as n>
${n}
</#list>
</#assign>
${x}
The above code will produce the following output: Monday Tuesday Wednesday Thursday Friday Saturday Sunday
Although assign specifies the usage of this complex variable value, we should not abuse this usage, as shown in the following example: <#assign x>Hello ${user}!</#assign>, it is more appropriate to change the above code to the following writing method: <#assign x="Hello ${user}!">
4.9 setting command
This instruction is used to set the FreeMarker running environment. The syntax format of this instruction is as follows: <#setting name=value>. In this format, the value range of name includes the following:
locale: This option specifies the country/language option used by the template
number_format: Specify the format for formatting the output number
boolean_format: Specify the syntax format of two boolean values, the default value is true, false
date_format,time_format,datetime_format: Specify the format for formatting the output date
time_zone: Set the time zone used when formatting the output date
4.10 macro , nested , return command
Macro can be used to implement custom instructions. By using custom instructions, a template fragment can be defined as a user instruction. The syntax format of using macro instructions is as follows:
<#macro name param1 param2 ... paramN>
...
<#nested loopvar1, loopvar2, ..., loopvarN>
...
<#return>
...
</#macro>
In the above format fragment, the following parts are included:
The name:name attribute specifies the name of the custom directive. Multiple parameters can be passed in when using the custom directive.
paramX: This property specifies the use of custom instruction time parameters. When using this custom instruction, values must be passed to these parameters.
nested directive: the middle part of the nested tag output when using custom directives
Loop variable in nested directive: This loop variable will be specified by the macro definition part and passed to the template using the label
return directive: This directive can be used to end the custom directive at any time.
See the following example:
<#macro book> //Define a custom directive
j2ee
</#macro>
<@book /> //Use the commands defined just now
The output result of the above code is: j2ee
In the above code, it may be difficult to see the usefulness of custom tags, because the content contained in the book directive we define is very simple. In fact, custom tags can contain a lot of content, so that better code reuse can be achieved. In addition, when defining custom instructions, you can also specify parameters for custom instructions, see the following code:
<#macro book booklist> //Define a custom directive booklist as a parameter
<#list booklist as book>
${book}
</#list>
</#macro>
<@book booklist=["spring","j2ee"] /> //Use the command you just defined
The above code passes a parameter value for the book instruction, and the output result of the above code is: spring j2ee
Not only that, you can also use nested directives to output the middle part of the custom instruction when customizing the instruction, see the following example:
<#macro page title>
<html>
<head>
<title>FreeMarker sample page - ${title?html}</title>
</head>
<body>
<h1>${title?html}</h1>
<#nested> //Tag body used to introduce user-defined instructions
</body>
</html>
</#macro>
The above code defines an HTML page template as a page directive, so the page directive can be used in other pages:
<#import "/" as com> //Suppose the above template page is named, import the page
<@ title="book list">
<u1>
<li>spring</li>
<li>j2ee</li>
</ul>
</@>
As can be seen from the above example, using macro and nested instructions can easily achieve page decoration effect. In addition, you can also specify one or more loop variables when using nested instructions, see the following code:
<#macro book>
<#nested 1> //A loop variable value is specified when using the book instruction
<#nested 2>
</#macro>
<@book ;x> ${x} .Book</@book>
When passing in variable values using nested directives, when using the custom directive, you need to use a placeholder (such as after the book directive; x). The above code output text is as follows:
1. Books 2. Books
When using loop variables in nested directives, multiple loop variables can be used, see the following code:
<#macro repeat count>
<#list 1..count as x> //Three loop variables are specified when using nested directive
<#nested x, x/2, x==count>
</#list>
</#macro>
<@repeat count=4 ; c halfc last>
${c}. ${halfc}<#if last> Last! </#if>
</@repeat>
The above output is:
1. 0.5 2. 1 3. 1.5 4. 2 Last;
The return instruction is used to end the macro instruction. Once the return instruction is executed in the macro instruction, FreeMarker will not continue to process the contents in the macro instruction. See the following code:
<#macro book>
spring
<#return>
j2ee
</#macro>
<@book />
The above code outputs: spring, and j2ee is located after the return instruction and will not output.
if, else, elseif
switch, case, default, break
list, break
include
Import
compress
escape, noescape
assign
global
setting
macro, nested, return
t, lt, rt
3 Some common methods or precautions
Expression conversion class
Digital loop
Take integers for floating point
Give the default value of the variable
Determine whether the object is null
Common formatting dates
Add global shared variable data model
Directly calling java object methods
String processing (built-in method)
Initialize sequences and hashes in the template
Comment flag
Built-in sequences method
Hashes built-in method
4 Things to note in freemarker in web development
Several commonly used objects in the web
Search order of values in view
Use tags in ftl in template
How to initialize shared variables
Integrate configuration with webwork
5 Advanced Methods
Custom Method
Custom Transforms
1 concept
The 3 most commonly used concepts
sequence sequence, corresponding to a collection of non-key-value pairs such as list, array, etc. in java
hash Collection of key-value pairs
namespace is a reference to an ftl file. This name allows you to access the resources of the ftl file.
2 commands
if, else, elseif
grammar
<#if condition>
...
<#elseif condition2>
...
<#elseif condition3>
...
...
<#else>
...
</#if>
Use Cases
<#if x = 1>
x is 1
</#if>
<#if x = 1>
x is 1
<#else>
x is not 1
</#if>
switch, case, default, break
grammar
<#switch value>
<#case refValue1>
...
<#break>
<#case refValue2>
...
<#break>
...
<#case refValueN>
...
<#break>
<#default>
...
</#switch>
Use Cases
String
<#switch >
<#case "small">
This will be processed if it is small
<#break>
<#case "medium">
This will be processed if it is medium
<#break>
<#case "large">
This will be processed if it is large
<#break>
<#default>
This will be processed if it is neither
</#switch>
number
<#switch x>
<#case x = 1>
1
<#case x = 2>
2
<#default>
d
</#switch>
If x=1 output 1 2, x=2 output 2, x=3 output d
list, break
grammar
<#list sequence as item>
...
<#if item = "spring"><#break></#if>
...
</#list>
Keywords
item_index: is the subscript of the current value of the list
item_has_next: determine whether the list still has a value
Use Cases
<#assign seq = ["winter", "spring", "summer", "autumn"]>
<#list seq as x>
${x_index + 1}. ${x}<#if x_has_next>,</#if>
</#list>
Output
1. winter,
2. spring,
3. summer,
4. autumn
include
grammar
<#include filename>
or
<#include filename options>
options contain two properties
encoding=”GBK” encoding format
Whether parse=true is parsed as ftl syntax, default is true, false is introduced in text. Note that in the ftl file, Boolean values are directly assigned, such as parse=true, rather than parse=”true”
Use Cases
/common/Includes content
Copyright 2001-2002 ${me}<br>
All rights reserved.
Template file
<#assign me = "Juila Smith">
<h1>Some test</h1>
<p>Yeah.
<hr>
<#include "/common/" encoding=”GBK”>
Output result
<h1>Some test</h1>
<p>Yeah.
<hr>
Copyright 2001-2002 Juila Smith
All rights reserved.
Import
grammar
<#import path as hash>
Similar to the import in java, it imports the file, and then you can use the macro components that are imported into the file in the current file.
Use Cases
Assuming that the macro copyright is defined, we can use it in other template pages.
<#import "/libs/" as my>
<@ date="1999-2002"/>
"my" is called namespace in freemarker
compress
grammar
<#compress>
...
</#compress>
Used to compress empty space and blank lines
Use Cases
<#assign x = " moo \n\n ">
(<#compress>
1 2 3 4 5
${moo}
test only
I said, test only
</#compress>)
Output
(1 2 3 4 5
moo
test only
I said, test only)
escape, noescape
grammar
<#escape identifier as expression>
...
<#noescape>...</#noescape>
...
</#escape>
Use Cases
It mainly uses similar string variable outputs. For example, all string outputs of a certain module must be html-safe. This expression can be used at this time.
<#escape x as x?html>
First name: ${firstName}
<#noescape>Last name: ${lastName}</#noescape>
Maiden name: ${maidenName}
</#escape>
Same expression
First name: ${firstName?html}
Last name: ${lastName }
Maiden name: ${maidenName?html}
assign
grammar
<#assign name=value>
or
<#assign name1=value1 name2=value2 ... nameN=valueN>
or
<#assign same as above... in namespacehash>
or
<#assign name>
capture this
</#assign>
or
<#assign name in namespacehash>
capture this
</#assign>
Use Cases
Generate variables and assign values to the variables
Assign sequence values to seasons
<#assign seasons = ["winter", "spring", "summer", "autumn"]>
Add 1 to the variable test
<#assign test = test + 1>
Assign a variable bgColor to my namepage, you can access this variable below
<#import "/" as my>
<#assign bgColor="red" in my>
Save a piece of output text as a variable in x
The text output in the shadowed part below will be assigned to x
<#assign x>
<#list 1..3 as n>
${n} <@myMacro />
</#list>
</#assign>
Number of words: ${x?word_list?size}
${x}
<#assign x>Hello ${user}!</#assign> error
<#assign x=” Hello ${user}!”> true
It also supports Chinese assignment, such as:
<#assign syntax>
java
</#assign>
${Syntax}
Printout:
java
global
grammar
<#global name=value>
or
<#global name1=value1 name2=value2 ... nameN=valueN>
or
<#global name>
capture this
</#global>
Global assignment syntax, using this syntax to assign values to a variable, then this variable is visible in all namespaces. If this variable is overwritten by the current assign syntax, such as <#global x=2> <#assign x=1> In the current page, x=2 will be hidden, or accessed through ${.}
setting
grammar
<#setting name=value>
Used to set up an environment for the entire system
locale
number_format
boolean_format
date_format, time_format, datetime_format
time_zone
classic_compatible
Use Cases
If the current setting is Hungarian, then modify it to the United States
${1.2}
<#setting locale="en_US">
${1.2}
Output
1,2
1.2
Because Hungary uses "," as the decimal separator, the United States uses "."
macro, nested, return
grammar
<#macro name param1 param2 ... paramN>
...
<#nested loopvar1, loopvar2, ..., loopvarN>
...
<#return>
...
</#macro>
Use Cases
<#macro test foo bar="Bar" baaz=-1>
Test text, and the params: ${foo}, ${bar}, ${baaz}
</#macro>
<@test foo="a" bar="b" baaz=5*5-2/>
<@test foo="a" bar="b"/>
<@test foo="a" baaz=5*5-2/>
<@test foo="a"/>
Output
Test text, and the params: a, b, 23
Test text, and the params: a, b, -1
Test text, and the params: a, Bar, 23
Test text, and the params: a, Bar, -1
Define the macro that loops out
<#macro list title items>
<p>${title?cap_first}:
<ul>
<#list items as x>
<li>${x?cap_first}
</#list>
</ul>
</#macro>
<@list items=["mouse", "elephant", "python"] title="Animals"/>
Output result
<p>Animals:
<ul>
<li>Mouse
<li>Elephant
<li>Python
</ul>
Macros containing body
<#macro repeat count>
<#list 1..count as x>
<#nested x, x/2, x==count>
</#list>
</#macro>
<@repeat count=4 ; c halfc last>
${c}. ${halfc}<#if last> Last!</#if>
</@repeat>
Output
1. 0.5
2. 1
3. 1.5
4. 2 Last!
t, lt, rt
grammar
<#t> Remove left and right blanks and enter to wrap
<#lt>Remove the blank on the left and enter the car and line
<#rt>Remove the blank on the right and enter the car and line
<#nt>Cancel the above effect
3 Some common methods or precautions
Expression conversion class
${expression} calculates expression and outputs
#{ expression }numeric calculation#{ expression ;format}In the format output numeric format is M and m
M represents the number of digits after the decimal point, m represents the number of digits after the decimal point, such as #{121.2322;m2M2} output 121.23
Digital loop
1..5 means from 1 to 5, prototype number..number
Take integers for floating point
${123.23?int} Output 123
Give the default value of the variable
${var?default("hello world<br>")?html}If var is null, it will be replaced by hello world<br>
Determine whether the object is null
<#if mouse?exists>
Mouse found
<#else>
You can also directly output a boolean shape by ${mouse?if_exists})
Common formatting dates
OpeningTime must be Date type, please view the freemarker document in detail Reference->build-in reference->build-in for date
${openingTime?date}
${openingTime?date_time}
${openingTime?time}
Add global shared variable data model
Implementation in code
cfg = ();
("global", "you good");
The page implementation can be done through the global command to view the global part in the command in detail.
Directly calling java object methods
${(args)}
String processing (built-in method)
html safe output
“abc<table>sdfsf”?html
Return safe html output, replace html code
xml safe output
var?xml
Usage of substring
<#assign user=”hello jeen”>
${user[0]}${user[4]}
${user[1..4]}
Output:
ho
ello
Similar usage
"abc;def;ghi"?split(";") returns sequence
Convert the string into sequence by space, and then take the length of the sequence
var?word_list The effect is the same as var?split(" )
var?word_list?size
Get string length
var?length
Caps output characters
var?upper_case
Lowercase output characters
var?lower_case
First character capitalization
var?cap_first
Lowercase first character
var?uncap_first
Remove the spaces before and after the string
var?trim
Capitalize the first character of each word
var?capitalize
similar:
"babcdabcd"?index_of("abc") Return 1
"babcdabcd"?index_of("abc",2) Return 5
similar
last_index_of and similar, same as above
The following two may be used when generating code (add "\" before quotation marks)
j_string: add "\" before string quotation marks
<#assign beanName = 'The "foo" bean.'>
String BEAN_NAME = "${beanName?j_string}";
Printout:
String BEAN_NAME = "The \"foo\" bean.";
js_string:
<#assign user = "Big Joe's \"right hand\".">
<script>
alert("Welcome ${user}!");
</script>
Print Out
alert("Welcome Big Joe\'s \"right hand\"!");
Replace string replace
${s?replace(‘ba’, ‘XY’ )}
${s?replace('ba', 'XY', 'rule parameters')} Replace all ba in s with xy Rule parameters include: i r m s c f The specific meaning is as follows:
· i: Indistinguishable from upper and lower case.
· f: Replace only the first string with the replaced string
· r: XY is a regular expression
· m: Multi-line mode for regular expressions. In multi-line mode the expressions ^ and $ match just after or just before, respectively, a line terminator or the end of the string. By default these expressions only match at the beginning and the end of the entire string.
· s: Enables dotall mode for regular expressions (same as Perl singe-line mode). In dotall mode, the expression . matches any character, including a line terminator. By default this expression does not match line terminators.
· c: Permits whitespace and comments in regular expressions.
Initialize sequences and hashes in the template
sequences
1. [“you”,”me”,”he”]
2. 1..100
3. [ {“Akey”:”Avalue”},{“Akey1”:”Avalue1”},
{“Bkey”:”Bvalue”},{“Bkey1”:”Bvalue1”},
]
hashes {“you”:”a”,”me”:”b”,”he”:”c”}
Comment flag
<#--
Here is the comment
-->
The old version of freemarker uses the <#comment> comment </#comment> method
Built-in sequences method
sequence?first
Returns the first value of sequence; prerequisite sequence cannot be null
sequence?last
Return the last value of sequence
sequence?reverse
Reverse the value of sequence
sequence?size
Returns the size of sequence
sequence?sort
Sort sequence by the result of the object toString() inside
sequence?sort_by(value)
Sort sequence by the attribute value of the object inside
For example: The sequence contains 10 user objects, and the user object contains attributes such as name, age, etc.
sequence?sort_by(name) means that all users are sorted by
Hashes built-in method
hash?keys
Return all keys in hash, return result type sequence
hash?values
Return all values in hash, return result type sequence
4 Things to note in freemarker in web development
Freemarker and webwork integration
Several commonly used objects in the web
Use internal objects directly in the ftl file of Freemarker:
${Request ["a"]}
${RequestParameters["a"]}
${Session ["a"]}
${Application ["a"]}
${JspTaglibs ["a"]}
After integration with webwork, the configured servlet has been placed in the data model.
The following object exists in the view
We can print the req object in ftl ${req}
· req - the current HttpServletRequest
· res - the current HttpServletResponse
· stack - the current OgnlValueStack
· ognl - the OgnlTool instance
· webwork - an instance of FreemarkerWebWorkUtil
· action - the current WebWork action
· exception - optional the Exception instance, if the view is a JSP exception or Servlet exception view
Search order of values in view
${name} will look for name values in the following order
· freemarker variables
· value stack
· request attributes
· session attributes
· servlet context attributes
Use tags in ftl in template
Note that if the attribute value of the label is a number, then the attribute must be assigned to the value using the nubmer=123 method.
JSP page
<%@page contentType="text/html;charset=ISO-8859-2" language="java"%>
<%@taglib uri="/WEB-INF/" prefix="html"%>
<%@taglib uri="/WEB-INF/" prefix="bean"%>
<html>
<body>
<h1><bean:message key=""/></h1>
<html:errors/>
<html:form action="/query">
Keyword: <html:text property="keyword"/><br>
Exclude: <html:text property="exclude"/><br>
<html:submit value="Send"/>
</html:form>
</body>
</html>
Template ftl page
<#assign html=JspTaglibs["/WEB-INF/"]>
<#assign bean=JspTaglibs["/WEB-INF/"]>
<html>
<body>
<h1><@ key=""/></h1>
<@/>
<@ action="/query">
Keyword: <@ property="keyword"/><br>
Exclude: <@ property="exclude"/><br>
<@ value="Send"/>
</@>
</body>
</html>
How to initialize shared variables
1. Initialize the global shared data model
When freemark is used on the web, it does not support the initialization of shared data. It cannot be implemented during configuration initialization, but must be initialized through the ftl file. This cannot meet the main needs. We need to leave an interface when servlet init to initialize the shared data of the system
Specifically, it is integrated with webwork, because webwork itself provides integrated servlets. If you want to add global shared variables, you can implement them by modifying them. We can initialize global shared variables when this servlet is initialized.
Integrate configuration with webwork
Configuration
<servlet>
<servlet-name>freemarker</servlet-name>
<servlet-class></servlet-class>
<init-param>
<param-name>TemplatePath</param-name>
<param-value>/</param-value>
<!—Template loads the folder, here, relative to context root, recursively obtains all templates under the folder -->
</init-param>
<init-param>
<param-name>NoCache</param-name> <!—Whether to cache templates-->
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>ContentType</param-name>
<param-value>text/html</param-value>
</init-param>
<init-param>
<param-name>template_update_delay</param-name>
<!—Template update time, 0 means update every time, this is suitable for development time-->
<param-value>0</param-value>
</init-param>
<init-param>
<param-name>default_encoding</param-name>
<param-value>GBK</param-value>
</init-param>
<init-param>
<param-name>number_format</param-name>
<param-value>0.###########</param-value><!—Digital display format-->
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>freemarker</servlet-name>
<url-pattern>*.ftl</url-pattern>
</servlet-mapping>
5 Advanced Methods
Custom Method
${timer("yyyy-MM-dd H:mm:ss", x)}
${timer("yyyy-MM-dd ", x)}
In the template, in addition to calling methods through objects (${(args)}), you can also directly call methods implemented by java. The java class must implement the method of the interface TemplateMethodModel exec(List args). The following is an example of converting the millisecond time into the time output in the format as a sample.
public class LongToDate implements TemplateMethodModel {
public TemplateModel exec(List args) throws TemplateModelException {
SimpleDateFormat mydate = new SimpleDateFormat((String) (0)));
return (new Date(((String)(1)));
}
}
Put the LongToDate object into the data model
("timer", new IndexOfMethod());
Used in ftl template
<#assign x = "123112455445">
${timer("yyyy-MM-dd H:mm:ss", x)}
${timer("yyyy-MM-dd ", x)}
Output
2001-10-12 5:21:12
2001-10-12
Custom Transforms
Implement the function of custom <@transform> text or expression</@transform>, allowing parsing and conversion of the middle final text
Example: Implement the function of converting str into STR
The code is as follows:
import .*;
import .*;
import ;
class UpperCaseTransform implements TemplateTransformModel {
public Writer getWriter(Writer out, Map args) {
return new UpperCaseWriter(out);
}
private class UpperCaseWriter extends Writer {
private Writer out;
UpperCaseWriter (Writer out) {
= out;
}
public void write(char[] cbuf, int off, int len)
throws IOException {
(new String(cbuf, off, len).toUpperCase());
}
public void flush() throws IOException {
();
}
public void close() {
}
}
}
Then put this object into the data model
("upcase", new UpperCaseTransform());
In the view(ftl) page, you can use it as follows
<@upcase>
hello world
</@upcase>
Printout:
HELLO WORLD