MyBatis注解配置(CRUD)详解

CRUD注解：@Select,@Insert,@Update,@Delete。
配置项注解：@Options。
参数绑定注解：@Param, 将传入方法的参数绑定到 SQL 语句的参数上。
结果映射注解: @Results—— 结果映射列表；@Result—— 在列和属性或字段之间的单独结果映射。

CRUD注解

package com.vending.test;
import java.util.List;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Options;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
public interface UserMapper {
     /**
      * 增
      * @param user
      * @return
      */
     @Insert("insert into user(name,sex,age) values(#{name},#{sex},#{age})")
     @Options(useGeneratedKeys=true,keyProperty="id") //返回自增主键
     int saveUser(User user);

     /**
      * 删
      * @param user
      * @return
      */
     @Delete("Delete from user where user_id = #{userId}")
     int deleteById(@Param("userId") Integer id);

     /**
      * 改
      * @param user
      */
     @Update("update user set name=#{name},sex=#{sex},age=#{age} where id = #{id}")
     void updateById(User user);


    /**
      * 查
      * @param id
      * @return User
      */
    @Select(value = "select * from user where user_id = #{userId}")
    @Results({
            @Result(id = true, property = "id", column = "user_id"),
            @Result(property = "username", column = "username"),
            @Result(property = "password", column = "password"),
            @Result(property = "home_address", column = "homeAddress")})
    User queryById(@Param("userId") Integer id);

     /**
      * 查-返回集合
      * @return List<User>
      */
     @Select("select * from user")
     List<User> queryAll();
}

关系映射注解

1. 一对一注解

    public interface UserMapper{
   
        /**
          * 一对一关联注解：需要关联执行的SQL语句
          * fetchType表示查询时是立即加载(eager)还是懒加载(lazy)
          * @param id
          * @return
          */
         @Select("select * from user where id = #{id}")
         @Results({
               @Result(id=true,column="id",property="id"),
               @Result(column="name",property="name"),
               @Result(column="sex",property="sex"),
               @Result(column="age",property="age"),
               @Result(column="card_id",property="card",
              one=@One(select="com.vending.mapper.CardMapper.selectCardById",
               fetchType=FetchType.EAGER))})
         User selectUserById(Integer id);
    }
   

2. 一对多注解

     /**
       * 一对多关联注解
       * @param id
       * @return
       */
     public interface ClazzMapper { 
   
         @Select("SELECT * FROM TB_CLAZZ  WHERE ID = #{id}") 
         @Results({ 
             @Result(id=true,column="id",property="id"), 
             @Result(column="code",property="code"), 
             @Result(column="name",property="name"), 
             @Result(column="id",property="students", 
             many=@Many( 
                     select="com.mapper.StudentMapper.selectByClazzId", 
                     fetchType=FetchType.LAZY)) 
         }) 
         Clazz selectById(Integer id); 
    }