MyBatis学习笔记（三）查询集合配置

第一节中查询的方法返回类型为Student，当返回类型为List<Student>时怎么办呢？

这时需要配置resultMap标签．

<?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:Mapper映射 -->
<!-- 这个文件感觉就像StudentMapper接口的实现一样，只是从java文件变成了xml文件
充当了Dao类的功能
 -->
<mapper namespace="com.skymr.mybatis.mappers.StudentMapper">
    <select id="getStudent" parameterType="int" resultType="Student">
        <!-- mybatis要自己写sql语句 -->
        select * from mybatis_Student where id=#{id}
    </select>

    <!-- 查询所有学生 -->
    <!-- resultMap属性要对应 resultMap的id属性 -->
    <select id="getAllStudents" resultMap="studentMap">
        select * from mybatis_Student
    </select>

    <resultMap type="Student" id="studentMap">
        <id property="id" column="id"/>
        <result property="name" column="name"/>
        <result property="age" column="age"/>
    </resultMap>
</mapper>

 

package com.skymr.mybatis.mappers;

import java.util.List;

import com.skymr.mybatis.model.Student;

public interface StudentMapper {

    public Student getStudent(int id);

    public List<Student> getAllStudents();
}

 

package com.skymr.mybatis.service;

import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.skymr.mybatis.mappers.StudentMapper;
import com.skymr.mybatis.model.Student;
import com.skymr.mybatis.util.MybatisUtil;

public class StudentTest2 {

    private Logger logger = LoggerFactory.getLogger(StudentTest2.class);

    private SqlSession session;

    @Before
    public void beforeTest(){
        session = MybatisUtil.openSession();
    }
    @After
    public void afterTest(){
        session.close();
    }

    @Test
    public void testGetAllStudents(){
        logger.info("测试取得所有学生");
        StudentMapper mapper = session.getMapper(StudentMapper.class);
        List<Student> list = mapper.getAllStudents();
        logger.info(list.toString());
    }
}