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 ： 

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 mapperPUBLIC "-//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();    }  }}