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  • Mybatis XML映射文件

    mybatis为聚焦于SQL而构建,SQL映射文件常用的顶级元素如

    • resultMap,是最复杂也是最强大的元素,用来描述如何从数据库结果集中来加载对象。 
    • insert,映射插入语句
    • update, 映射更新语句
    • delete , 映射删除语句
    • select , 映射查询语句

    1)简单的单表映射文件

    <?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper  PUBLIC "-//mybatis.org//DTD mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.mybatis.bean.userMapper">
        <select id="getUser" parameterType="int"  resultType="com.mybatis.bean.User">
            select * from users where id=#{id}
        </select>
    
        <insert id="insertUser" parameterType="com.mybatis.bean.User">
            insert into users(name,age) values(#{name},#{age});
        </insert>
    
        <update id="updateUser" parameterType="com.mybatis.bean.User">
           update  users set name=#{name} ,age=#{age} where id=#{id}
        </update>
    
        <delete id="deleteUser" parameterType="int">
            delete from users where id=#{id}
        </delete>
    
        <select id="allUser" resultType="com.mybatis.bean.User">
            select * from users
        </select>
    </mapper>
    

    Java对象

    public class User {
    
        private int id;
        private String name;
        private int age;
    
        public int getId() {
            return id;
        }
    
        public String getName() {
            return name;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
     
    }
    

     2)结果映射resultMap 元素是 MyBatis 中最重要最强大的元素。当列名和属性名没有精确匹配,可以在SELECT语句中对列使用别名,或配置显式的结果映射。

    Java对象

    public class Classes {
      
        private int id;
        private String name;
        private Teacher teacher; 
        // 省略
    }
    

    resultMap映射文件、关联对象

    <?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.mybatis.bean.ClassMapper">
        <select id="getClass" parameterType="int" resultMap="ClassResultMap">
           select * from class c,teacher t where c.teacher_id = t.t_id and c.c_id=#{id}
        </select>
    
        <resultMap id="ClassResultMap" type="classes">
         <id property="id" column="c_id"/>
         <result property="name" column="c_name"/>
         <association property="teacher" column="teacher_id" javaType="teacher">
               <id property="id" column="t_id"/>
               <result property="name" column="t_name"/>
         </association>
        </resultMap>
        
    </mapper>
    

    集合配置

    <collection property="posts" ofType="domain.blog.Post">
      <id property="id" column="post_id"/>
      <result property="subject" column="post_subject"/>
      <result property="body" column="post_body"/>
    </collection>
    

     

    参考文献:mybatis官网http://www.mybatis.org/mybatis-3/zh/sqlmap-xml.html

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  • 原文地址:https://www.cnblogs.com/walkwithmonth/p/11371685.html
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