MyBatis(2)：CRUD操作

编写接口

import com.shandx.pojo.User;
import java.util.List;
public interface UserMapper {
//获取全部的用户

List<User> selectUser();
//通过id查找用户

User selectUserById(int id);
//增加用户

int addUser(User user);
//通过id删除用户

int deleteUserById(int id);
//更新用户

int updateUser(User user);
}

对应的mapper语句编写

<?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">
<!--mapper标签的namespace对应Mapper接口的类-->

<mapper namespace="com.shandx.dao.UserMapper">
<!--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-->

<!--获取全部的用户-->

<select id="selectUser" resultType="com.shandx.pojo.User">

select * from user

</select>
<!--通过id查找用户-->

<select id="selectUserById" resultType="com.shandx.pojo.User">

select *from user where id=#{id}

</select>
<!--增加用户-->

<insert id="addUser" parameterType="com.shandx.pojo.User">

insert into user (id,name,pwd) values (#{id},#{name},#{pwd})

</insert>
<!--通过id删除用户-->

<delete id="deleteUserById" parameterType="com.shandx.pojo.User">

delete from user where id=#{id}

</delete>
<!--更新用户-->

<update id="updateUser" parameterType="com.shandx.pojo.User">

update user set name=#{name},pwd=#{pwd} where id=#{id}

</update>
</mapper>

测试类

import com.shandx.dao.UserMapper;
import com.shandx.pojo.User;
import com.shandx.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.Test;
import java.util.List;
public class UserMapperTest {

@Test  //获取全部的用户

public void selectUser() {

//1.拿到sqlSessionFactory对象

SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();

//2.通过sqlSessionFactory对象openSession()创建一个sqlSession。

SqlSession sqlSession = sqlSessionFactory.openSession();

//3.通过sqlSession获得mapper对象 ， 参数为映射文件对应的接口类的class对象

UserMapper mapper = sqlSession.getMapper(UserMapper.class);

//4.通过mapper对象来执行操作；

List<User> users = mapper.selectUser();

//获得结果集

for (User user : users) {

System.out.println(user);

}

}
@Test //通过id查找用户

public void selectUserById(){

SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();

SqlSession sqlSession = sqlSessionFactory.openSession();

UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = mapper.selectUserById(2);

System.out.println(user);

}
@Test    //增加用户

public void addUser(){

SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();

SqlSession sqlSession = sqlSessionFactory.openSession();

UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = new User(5, "shandianxia", "521");

int i = mapper.addUser(user);

if(i>0){

System.out.println("插入成功！！！");

}

sqlSession.commit();//提交事务

sqlSession.close();//关闭

}
@Test //通过id删除用户

public void deleteUserById(){

SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();

SqlSession sqlSession = sqlSessionFactory.openSession();

UserMapper mapper = sqlSession.getMapper(UserMapper.class);
int i = mapper.deleteUserById(5);

if(i>0){

System.out.println("删除成功！！！");

}

sqlSession.commit();//提交事务

sqlSession.close();//关闭

}
@Test //更新用户

public void updateUser(){

SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();

SqlSession sqlSession = sqlSessionFactory.openSession();

UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = new User(3, "雷神", "456");

int i = mapper.updateUser(user);

if(i>0){

System.out.println("更新成功！！！");

}

sqlSession.commit();//提交事务

sqlSession.close();

}
}

总结CRUD注意点

1，增删改查需要提交事务
2，如果出现乱码，先在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"

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