1. Find the AbstractSqlInjector abstract implementation class through the ISqlInjector interface, and then find the DefaultSqlInjector class. It is the default SQL injector of mybatis-plus. If the project uses logical deletion, then another LogicSqlInjector may be configured. Our project uses LogicSqlInjector. I found that there is a ListgetMethodList() method inside, which returns a collection. Each AbstractMethod in the collection is the Sql method that extends Mybatis-plus to Mybatis.
2. What we want to extend this time is a method that can query the object according to id, regardless of whether the object has been deleted or not, findById(Integerid). Therefore, we imitate LogicSelectById to write a class inheritance AbstractMethod
3. The Mybatis-plus default interface BaseMapper we inherited does not have the findById method we want to use, so we write an interface MyBaseMapper to inherit the BaseMapper interface, and then inherit the MyBaseMapper of our business mapper. In this way, our business mapper has the findById method.
4. In order to inject the FindById we created into Mybatis-plus, we write a class inherits LogicSqlInjector, rewrites its getMethodList() method, and adds our FindById into it.
5. Configure the Sql injector we created in Spring IOC to make it take effect