Mybatis 入门之resultMap与resultType讲解实例

悠悠 2022-08-19 11:28 203阅读 0赞

resultMap：适合使用返回值是自定义实体类的情况

resultType：适合使用返回值得数据类型是非自定义的，即jdk的提供的类型

resultMap ：

映射实体类的数据类型

resultMap的唯一标识

column: 库表的字段名

property： 实体类里的属性名

配置映射文件：

<?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.hao947.sql.mapper.PersonMapper">
      
      <resultMap type="person" id="BaseResultMap">
        
        <id column="person_id" property="personId" />
        <result column="name" property="name" />
        <result column="gender" property="gender" />
        <result column="person_addr" property="personAddr" />
        <result column="birthday" property="birthday" />
      </resultMap>
      
    
      
      <select id="selectPersonById" parameterType="java.lang.Integer"
        resultMap="BaseResultMap">
        select * from person p where p.person_id = #{id}
      </select>
      
      <select id="selectPersonCount" resultType="java.lang.Integer">
        select count(*) from
        person
      </select>
    
      <select id="selectPersonByIdWithMap" parameterType="java.lang.Integer"
        resultType="java.util.Map">
        select * from person p where p.person_id= #{id}
        </select>
    
    </mapper>

实体类Person.java

<pre name="code" class="java">package com.hao947.model;
    import java.util.Date;
    public class Person {
        
      private Integer personId;
      private String name;
      private Integer gender;
      private String personAddr;
      private Date birthday;
      @Override
      public String toString() {
        return "Person [personId=" + personId + ", name=" + name + ", gender="
            + gender + ", personAddr=" + personAddr + ", birthday="
            + birthday + "]";
      }
    }

测试类

public class PersonTest {
        
      SqlSessionFactory sqlSessionFactory;
      @Before
      public void setUp() throws Exception {
        // 读取资源流
        InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
        // 初始化session工厂
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
      }
    
      
    
      @Test
      public void selectPersonById() {
        // 创建一个sqlsession
        SqlSession session = sqlSessionFactory.openSession();
        try {
          Person p = session.selectOne(
              "com.hao947.sql.mapper.PersonMapper.selectPersonById", 1);
          System.out.println(p);
        } finally {
          session.close();
        }
      }
      @Test
      public void selectPersonCount() {
        // 创建一个sqlsession
        SqlSession session = sqlSessionFactory.openSession();
        try {
          Integer p = session.selectOne(
              "com.hao947.sql.mapper.PersonMapper.selectPersonCount");
          System.out.println(p);
        } finally {
          session.close();
        }
      }
      @Test
      public void selectPersonByIdWithMap() {
        // 创建一个sqlsession
        SqlSession session = sqlSessionFactory.openSession();
        try {
          Map<String ,Object> map = session.selectOne(
              "com.hao947.sql.mapper.PersonMapper.selectPersonByIdWithMap",1);
          System.out.println(map);
        } finally {
          session.close();
        }
      }
    }