Mapper动态代理

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测试环境一定要配置好（mybatis.xml，MyBatisUtil.java）

见https://blog.csdn.net/Yuan52007298/article/details/81413042

Mapper动态代理省略了接口方法的实现，减少代码书写量。使用更方便快捷。

动态代理的方法就是使映射文件的namspace指向接口方法。要求：方法名必须和映射sql语句id相同

 （1）方法接口（不必写实现类）

package com.Demo.Dao;

import java.util.List;
import java.util.Map;

import com.Demo.Entity.Student;

public interface StudentDao {
	void insertStudent(Student student);
	void insertStudentReturnId(Student student);
	void deleteStudent(Integer id);
	void updateStudent(Student student);
	List<Student> selectAllStudent();
	Student selectStudentById(Integer id);
	List<Student> selectStudentLimit(Map map);
}

（2）mapper.xml （记得在mybatis.xml文件中把映射文件注册了）

<?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">

<!-- 注意namespace的指向 -->
<mapper namespace="com.Demo.Dao.StudentDao">

<!-- 解决数据库字段名与实体属性字段名不一致映射 -->
	<resultMap type="Student" id="studentMapper">
		<id column="id" property="id"/>
		<result column="name" property="name"/>
		<result column="age" property="age"/>
		<result column="score" property="score"/>
	</resultMap>
	
	<insert id="insertStudent" parameterType="com.Demo.Entity.Student">
		insert into student(name,age,score) values(#{name},#{age},#{score})
	</insert>
	
	<!-- 使用别名 -->
	<insert id="insertStudentReturnId" parameterType="Student">
		insert into student(name,age,score) values(#{name},#{age},#{score})
		<!-- mysql的自增主键在insert语句之后，所以AFTER。ORACLE数据库的逐渐自增在inert语句之前，所以BEFORE -->
		<selectKey resultType="int" keyProperty="id" order="AFTER">
			select @@identity
		</selectKey>
	</insert>
	
	<delete id="deleteStudent">
		<!-- #{xxx}是占位符，名称随意，参数自动填充 -->
		delete from Student where id = #{xxx}  
	</delete>
	
	<update id="updateStudent">
		update student set name=#{name},age=#{age},score=#{score} where id=#{id}
	</update>
	
	<!-- select结果数据集需要封装到实体类中，需要设置属性resultType -->
	<select id="selectAllStudent" resultType="Student">
		select id,name,age,score from student
	</select>
	
	<select id="selectStudentById" resultType="Student">
		select id,name,age,score from student where id=#{xxx}
	</select>
	
	<select id="selectStudentLimit" resultType="Student">
		select id,name,age,score from student LIMIT #{start},#{size}
	</select>
	
	<!-- 模糊查询 -->
		<select id="selectStudentByName" resultType="Student">
		<!-- select id,name,age,score from student where name like concat('%',#{xxx},'%') -->
		<!-- select id,name,age,score from student where name like '%' #{xxx} '%' -->
		select id,name,age,score from student where name like '%${value}%'
	</select>
</mapper>

（3）完成接口到SQL语句的映射后，就可以直接写测试了

package com.Demo.Test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

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

import com.Demo.Dao.StudentDao;
import com.Demo.Entity.Student;
import com.Demo.Utils.MyBatisUtil;

public class MyTest2 {
	@Before
	public void setUp() throws Exception {
	}

	@After
	public void tearDown() throws Exception {
	}

	@Test
	public void testInsert() {
		SqlSession sqlSesion = MyBatisUtil.getSqlSession();
		StudentDao dao = sqlSesion.getMapper(StudentDao.class);
		Student student = new Student("黄荣",23,89.9);
		
		dao.insertStudent(student);
		sqlSesion.commit();
		sqlSesion.close();
	}
	@Test
	public void testInsertReturnId() {
		SqlSession sqlSesion = MyBatisUtil.getSqlSession();
		StudentDao dao = sqlSesion.getMapper(StudentDao.class);
		Student student = new Student("乐呵呵",23,89.9); 
		System.out.println(student.toString());
		dao.insertStudentReturnId(student);
		sqlSesion.commit();
		sqlSesion.close();
		System.out.println(student.toString());
	}
	@Test
	public void deleteStudent() {
		SqlSession sqlSesion = MyBatisUtil.getSqlSession();
		StudentDao dao = sqlSesion.getMapper(StudentDao.class);
		dao.deleteStudent(11);
		sqlSesion.commit();
		sqlSesion.close();
	}
	@Test
	public void updateStduent() {
		SqlSession sqlSesion = MyBatisUtil.getSqlSession();
		StudentDao dao = sqlSesion.getMapper(StudentDao.class);
		Student student = new Student("范冰冰",24,89.9); 
		student.setId(1);
		dao.updateStudent(student);
		sqlSesion.commit();
		sqlSesion.close();
	}
	@Test
	public void selectAllStudent() {
		SqlSession sqlSesion = MyBatisUtil.getSqlSession();
		StudentDao dao = sqlSesion.getMapper(StudentDao.class);
		List<Student> stuList = dao.selectAllStudent();
		sqlSesion.commit();
		sqlSesion.close();
		for (Student student : stuList) {
			System.out.println(student.toString());
		}
	}
	@Test
	public void selectStudentById() {
		SqlSession sqlSesion = MyBatisUtil.getSqlSession();
		StudentDao dao = sqlSesion.getMapper(StudentDao.class);
		Student student =  dao.selectStudentById(1);
		sqlSesion.commit();
		sqlSesion.close();
		System.out.println(student.toString());
	}
	@Test
	public void selectStudentLimit() {
		Map<String,Integer> map = new HashMap<>();
		map.put("start", 1);
		map.put("size", 4);
		SqlSession sqlSesion = MyBatisUtil.getSqlSession();
		StudentDao dao = sqlSesion.getMapper(StudentDao.class);
		
		List<Student> studentList =  dao.selectStudentLimit(map);
		sqlSesion.commit();
		sqlSesion.close();
		for (Student student : studentList) {
			System.out.println(student.toString());
		}
		
	}
}