MyBatis学习总结（13）——Mybatis查询之resultMap和resultType区别

<?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>

<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 + "]";
}
}

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();
}
}
}