增删改查操作

mapper接口本质就是原来的Dao接口，知识为了方便我们的书写，一个mapper接口对应一个mapper映射文件

将UserMapper更名为UserDao，说明本质

修改对应的mapper映射文件的namespace属性，对应上接口。

编写接口

 1 package com.like.dao;
 2
 3 import com.like.pojo.User;
 4
 5 import java.util.List;
 6
 7 public interface UserDao{
 8     //获取全部的用户
 9     List<User>selectUser();
10
11     //根据id查找用户
12     User electUserById(int id);
13
14     //添加一个用户
15     int addUser(User user);
16
17     //删除用户
18     int deleteUserByID(int id);
19
20     //修改用户
21     int updateUser(User user);
22  }

对应的mapper语句编写

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3         PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <!--mapper标签的namespace对应的Mapper接口的类，报名+类名-->
 6 <mapper namespace="com.like.dao.UserDao">
 7 <!--select标签的id对应映射接口的方法名字    resultType:返回结果的类型   中间就编写sql语句-->
 8 <select id="selectUser" resultType="com.like.pojo.User">
 9 select*from user
10 </select>
11 <select id="selectUserById" resultType="com.like.pojo.User">
12 select*from user where id =#{id}
13 </select>
14
15 <!--我们需要接受一个自定义的对象(引用队形) 需要设置parameterTpye,为参数类型
16       接收这个对象的值，直接使用#{对象字段名}
17 -->
18 <insert id="addUser" parameterType="com.like.pojo.User">
19 inset into user(id,name,pwd)values(#{id},#{name},#{pwd})
20 </insert>
21
22 <delete id="deleteUserByID" parameterType="int">
23 delete from user where id =#{id}
24 </delete>
25
26 <update id="updateUser" parameterType="com.like.pojo.User">
27 updata user set name=#{name},pwd=#{pwd}where id=#{id}
28 </update>
29 </mapper>

测试类

 1 package com.like.dao;
 2
 3 import com.like.dao.UserDao;
 4 import com.like.pojo.User;
 5 import dom.like.utils.MyBatisUtils;
 6 import org.apache.ibatis.session.SqlSession;
 7 import org.apache.ibatis.session.SqlSessionFactory;
 8 import org.junit.Test;
 9 import java.util.List;
10
11 public class UserMapperTest{
12
13   @Test
14   public void selectUser(){
15    //1.拿到sqlSessionFactory对象
16   SqlSessionFactory sqlSessionFactory=MyBatisUtils.getSqlSessionFactory();
17   //2.通过sqlSessionFactory对象openSession()创建一个sqlSession.
18   SqlSession sqlSession =sqlSessionFactory.openSession();
19   //3.通过sqlSession获得mapper对象，参数为映射文件对应的接口类的class队形
20   UserDao mapper =sqlSession.getMapper(UserDao.class);
21   //4.通过mapper对象来执行操作；
22   List<User>users =mapper.selectUser();
23   //获得结果集
24   for (User user : users){
25   System.out.println(user);
26 }
27 sqlSession.close();//关闭sqlSession
28
29 }
30 @Test
31     public void addUser(){
32         User user = new User(4,"qinjiang","123456");
33
34         SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();
35         SqlSession sqlSession = sqlSessionFactory.openSession();
36         UserDao mapper = sqlSession.getMapper(UserDao.class);
37
38         int i = mapper.addUser(user);
39
40         //没有插入成功的原因：没有提交事务；
41         sqlSession.commit(); //提交事务
42         sqlSession.close(); //关闭sqlSession
43
44         if (i>0){
45             System.out.println("插入成功！");
46         }
47
48     }
49
50     @Test
51     public void deleteUserByID(){
52         SqlSession sqlSession = MyBatisUtils.getSqlSessionFactory().openSession();
53         UserDao mapper = sqlSession.getMapper(UserDao.class);
54         int i = mapper.deleteUserByID(4);
55
56         //记得提交事务，否则删除不成功！
57         sqlSession.commit();//提交事务
58         sqlSession.close();//关闭
59
60         if (i>0){
61             System.out.println(i);
62         }
63     }
64
65     @Test
66     public void updateUser(){
67         SqlSession sqlSession = MyBatisUtils.getSqlSessionFactory().openSession();
68         UserDao mapper = sqlSession.getMapper(UserDao.class);
69         User user = new User(1,"李柯","like");
70         mapper.updateUser(user);
71
72         sqlSession.commit();
73         sqlSession.close();
74
75     }
76 }

注意点总结

增改删需要提交事务！

如果出现乱码，现在sql中进行测试，sql没问题，就检查配置文件

jdbc:mysql://localhost:3306/mybatis?
useSSL=true&useUnicode=true&characterEncoding="utf-8"

参数问题

如果时基本数据类型，可以省略，但建议写上    引用类型必须写指定的  包名+类名。

原文地址：https://www.cnblogs.com/like-lry/p/11320291.html