Java implementation of Base64 encryption & decryption methods

1. Base64encryptionalgorithm

1.1 Standard Base64 Algorithm

Base64 encoding is a coding algorithm commonly used in program development. It is a method commonly used to store or transmit some binary data. It is also an encoding method in MIME (Multi-purpose Internet Mail Extension).

Base64 can implement anyData conversionAs a string represented by printable characters to avoid distortion of data during transmission, Base64 was initially used to convert non-ASCLL characters into ASCLL characters during mailing.

Standard Base64 is one of the encoding methods used to transmit 8Bit bytecode. It represents binary data based on 64 printable characters. The printable characters used include: A-Z, a-z, 0-9, +, / in total.

1.2 Non-standard Base64 algorithm

UrlBase64

The + and / characters are used in the standard Base64 algorithm, which conflicts with URLs and file systems, so a UrlBase64 algorithm is extended to replace the + and / of the standard Base64 into the - and _ characters.

MIME Base64

The MIME Base64 algorithm is a more friendly oneEncoding format, which defines that only 76 characters can be output per line. If the length exceeds 76, a line break will be performed and a line break symbol will be added at the end of the line.\r\n, The length of the last line of characters is less than 76 immediately, and the carriage return line break symbol will also be added.

3. Java implements Base64 encryption and decryption

3.1 apache.commons-codex package

Many encoding format conversions such as Base64 provided in the -codex package can be implemented through it.

import .Base64;
public class Base64Util {

    //base64 encoding    public static String encode(byte[] bytes) {
        return new String(Base64.encodeBase64(bytes));
    }
    
    //base64 decoding    public static String decode(byte[] bytes) {
        return new String(Base64.decodeBase64(bytes));
    }
    
    public static void main(String[] args) {
        String string = "test1234";
        //coding        String encode = encode(());
        (string + "\tThe encoded string is:" + encode);
        //decoding        String decode = decode(());
        (encode + "\tAfter decoding the string, it is:" + decode);
    }
}
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3.2 Base64 in Java8

After Java8, the Base64 feature is provided in the JDK toolkit, which can be used directly to complete encoding and decoding operations.

import ;
import .Base64;
public class Base64Util {

final static  encoder = ();
final static  decoder = ();

    public static String encode(String text) {
        return ((StandardCharsets.UTF_8));
    }

    public static String decode(String encodedText) {
        return new String((encodedText), StandardCharsets.UTF_8);
    }
    
    public static void main(String[] args) {
        String str = "test1234";

        ("The encoded string is:");
        ((str));

        ("The decoded string is:");
        (((str)));
    }
}
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Use UTF-8 to specify the encoding and decoding format to ensure that there will be no Chinese garbled problems during operation. If the encoding format is not specified, Base64 will use the environment default encoding format.
windowsThe default is GBK encoding, while the default is utf-8 encoding on Linux. Therefore, it is a good programming habit to specify a unified encoding format when encoding and decoding.

3.3 Non-standard Base64 encoding implementation

The Base64 package of Java8 also provides non-standard Base64 encoding methods.

UrlBase64

()
()

MimBease64

()
()

4. Base64 encoding of the picture

4.1 Picture to string

Java encodes the image to get Base64 string

public static String GetImageStr(String imgFilePath) {
    // Convert the image file into a byte array string and perform Base64 encoding processing    byte[] data = null;

    // Read the image byte array    try {
        InputStream in = new FileInputStream(imgFilePath);
        data = new byte[()];
        (data);
        ();

    } catch (IOException e) {
        ();
    }

    // Encoding the byte array Base64    BASE64Encoder encoder = new BASE64Encoder();
    // Returns Base64 encoded string of byte array    return (data);
}
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If you need to display the resulting base64 string in the img tag of html, you need to add it to the stringdata:image/jpg;base64,Prefix

&lt;img src="data:image/jpg;base64,..." /&gt;
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4.2 Base64 string to picture

For standard Base64 strings, you can also directly use the Base64 decoding method to convert it to an image file. However, if it is a string in the img tag, you need to remove the specific prefix and convert it to an image, otherwise the image cannot be opened.

public static void base642Image(String imgData) {
    // Base64 string null    if (imgData == null) {
        return ;
    }

    String imgFilePath = "C:\\Desktop\\temp\\";
    BASE64Decoder decoder = new BASE64Decoder();
    OutputStream out = null;
    try {
        out = new FileOutputStream(imgFilePath);
        byte[] bytes = (imgData);
        for (int i = 0; i &lt; ; ++i) {
            if (bytes[i] &lt; 0) {
                bytes[i] += 256;
            }
        }
        (bytes);
        ();
        ();
    } catch (Exception e) {
        ();
    }
}
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