Mybatis 入门之resultMap与resultType讲解实例

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 ： 

type：映射实体类的数据类型

id：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">
<!-- namespace:当前库表映射文件的命名空间，唯一的不能重复 -->
<mapper namespace="com.hao947.sql.mapper.PersonMapper">
    <!-- type:映射实体类的数据类型 id：resultMap的唯一标识 -->
    <resultMap type="person" id="BaseResultMap">
        <!-- column:库表的字段名 property:实体类里的属性名 -->
        <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>
    <!--id:当前sql的唯一标识
         parameterType：输入参数的数据类型
         resultType：返回值的数据类型
         #{}:用来接受参数的，如果是传递一个参数#{id}内容任意，如果是多个参数就有一定的规则,采用的是预编译的形式select
        * from person p where p.id = ? ，安全性很高 -->

    <!-- sql语句返回值类型使用resultMap -->
    <select id="selectPersonById" parameterType="java.lang.Integer"
        resultMap="BaseResultMap">
        select * from person p where p.person_id = #{id}
    </select>
    <!-- resultMap:适合使用返回值是自定义实体类的情况
    resultType：适合使用返回值的数据类型是非自定义的，即jdk的提供的类型 -->
    <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();
        }
    }
}