初窺MyBatis-普通的CRUD操作

• 撰寫介面
• 撰寫對應的Mapper.xml中的sql陳述句
• 測驗（增刪改需要提交事務）

<mapper namespace="com.perwrj.dao.UserMapper">
<!-- 查詢 id=“重寫的方法名” resultType=“回傳值型別（全類名）” -->
  <select id="getUserList" resultType="com.perwrj.pojo.User">
    select * from mybatis.user
  </select>
</mapper>

• id：就是對應的namespace中的方法名
• resultType：sql陳述句的回傳值型別
• parameterType：傳入引數的型別

package com.perwrj.dao;

import java.util.List;

import com.perwrj.pojo.User;

public interface UserMapper {
//	查詢全部用戶
	List<User> getUserList();
//	根據id查詢用戶
	User getUserById(int id);
//	添加一個用戶
	int addUser(User user);
//	修改用戶
	int updateUser(User user);
//	洗掉用戶
	int deleteUser(int id);
}

<?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系結一個對應的Mapper/Dao介面 -->
<mapper namespace="com.perwrj.dao.UserMapper">
<!-- 查詢 id=“重寫的方法名” resultType=“回傳值型別（全類名）” -->
  <select id="getUserList" resultType="com.perwrj.pojo.User">
    select * from mybatis.user
  </select>
  
   <select id="getUserById" parameterType="int" resultType="com.perwrj.pojo.User">
    select * from mybatis.user where id = #{id}
  </select>
  <!-- 物件中的屬性可以直接取出來 -->
  <insert id="addUser" parameterType="com.perwrj.pojo.User">
  	insert into mybatis.user (id,name,pwd) values (#{id},#{name},#{pwd})
  </insert>
  
  <update id="updateUser" parameterType="com.perwrj.pojo.User">
  	update mybatis.user set name = #{name},pwd = #{pwd} where id = #{id}
  </update>
  
  <delete id="deleteUser"  parameterType="int">
  	delete from mybatis.user where id = #{id}
  </delete>
</mapper>

package com.perwrj.dao;



import java.util.List;

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

import com.perwrj.pojo.User;
import com.perwrj.utils.MyBatisUtil;

public class UserMapperTest {
	@Test
	public void test() {
		//獲得SqlSession物件，
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		
		try {
//			方式一：getMapper執行sql:更加簡潔，型別更加安全，推薦使用
			
			  UserMapper userMapper = sqlSession.getMapper(UserMapper.class); List<User>
			  userList = userMapper.getUserList();
			
			  for (User user : userList) { System.out.println(user); }
	
			//方式一結束
			
//			方式二：老方法，不建議使用，
			/*
			 * List<User> list =
			 * sqlSession.selectList("com.perwrj.dao.UserMapper.getUserList");
			 * 
			 * for (User object : list) { System.out.println(object); }
			 */
			//方式二結束
		}catch(Throwable e) {
			e.printStackTrace();
		}finally {
//			關閉sqlSession
			sqlSession.close();
		}	
	}
	/**
	 * 洗掉操作
	 */
	@Test
	public void deleteUserTest() {
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		
		try {
			UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 
			int num = userMapper.deleteUser(4);
			if(num > 0) {
//				提交事務
				System.out.println(num);//1
				sqlSession.commit();
				sqlSession.close();
			}
		}catch(Throwable e) {
			e.printStackTrace();
		}finally {
			sqlSession.close();
		}		
	}
					
					
	
	
	/**
	 * 改操作
	 */
	@Test
	public void updateUserTest() {
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		
		try {
			UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 
			int num = userMapper.updateUser(new User(2,"杰瑞","987654"));
			if(num > 0) {
//				提交事務
				System.out.println(num);//1
				sqlSession.commit();
				sqlSession.close();
			}
		}catch(Throwable e) {
			e.printStackTrace();
		}finally {
			sqlSession.close();
		}			
	}
	
	/**
	 * 增刪改需要提交事務
	 */
	@Test
	public void addUserTest() {
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
				
		try {
			UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 
			int num = userMapper.addUser(new User(4,"王瑞杰","123568"));
			if(num > 0) {
//				提交事務
				System.out.println(num);//1
				sqlSession.commit();
				sqlSession.close();
			}
		}catch(Throwable e) {
			e.printStackTrace();
		}finally {
			sqlSession.close();
		}	
	}
	
	@Test
	public void testGetUserById() {
		//獲得SqlSession物件，
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		
		try {
			  UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 
			  User user = userMapper.getUserById(1);
			  System.out.println(user);
		}catch(Throwable e) {
			e.printStackTrace();
		}finally {
			sqlSession.close();
		}	
	}
	

}

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