MyBatis：CRUD 注解配置

　　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); 
   }