Mybatis的使用及增删改查

1 导入依赖

<!--建立meavn项目在pom.xml文件中导入依赖并配置资源加载-->
<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.2</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.6</version>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.22</version>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.18.18</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>

 <build>
    <resources>
      <resource>
        <directory>src/main/resources</directory>
        <includes>
          <include>**/*.properties</include>
          <include>**/*.xml</include>
        </includes>
        <filtering>true</filtering>
      </resource>
      <resource>
        <directory>src/main/java</directory>
        <includes>
          <include>**/*.properties</include>
          <include>**/*.xml</include>
        </includes>
        <filtering>true</filtering>
      </resource>
    </resources>

2 编写Mybatis核心文件

<!-- resources目录下创建mybatis-config核心配置文件-->
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=PRC"/>
                <property name="username" value="dbone"/>
                <property name="password" value="dbone"/>
            </dataSource>
        </environment>
    </environments>

    <!--  每一个Mapper.xml都需要在Mybatis核心配置文件中注册！  -->
    <mappers>
        <mapper resource="com/lyc/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

3 编写工厂类

//com.lyc.utis目录下编写MybatisUtis类
package com.lyc.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static{
        try {
            //获取SqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    //既然有了 SqlSessionFactory，
    // 顾名思义，我们可以从中获得 SqlSession 的实例。
    // SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。
    // 你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句

    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

4 编写实体类

//在com.lyc.pojo中编写实体类(与数据库的表相对应)
package com.lyc.pojp;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private int id;
    private String name;
    private String pwd;
}

5 编写接口

//在com.lyc.mapper中编写接口UserMapper文件(一个接口对应一个.xml文件)
package com.lyc.mapper;

import com.lyc.pojp.User;

import java.util.List;

public interface UserMapper {
    //查询全部用户
    List<User> getUserList();

    //根据ID查询用户
    User getUserByID(int id);

    //增加一个用户
    int addUser(User user);

    //修改用户
    int updateUser(User user);

    //删除用户
    int deleteUser(int id);
}

6 编写与接口对应的.xml文件

<!-- 在com.lyc.mapper目录中编写UserMapper.xml文件 -->
<?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绑定一个对应的/Dao/Mapper接口-->
<mapper namespace="com.lyc.mapper.UserMapper">
<!--select 查询语句-->
    <select id="getUserList" resultType="com.lyc.pojp.User">
        select * from mybatis.user
    </select>
    <select id="getUserByID" resultType="com.lyc.pojp.User" parameterType="int">
        select * from  mybatis.user where id = #{id}
    </select>
    <insert id="addUser" parameterType="com.lyc.pojp.User">
        insert into mybatis.user(id,name,pwd) values (#{id},#{name},#{pwd})
    </insert>
    <update id="updateUser" parameterType="com.lyc.pojp.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>

7 编写测试类

//编写测试类进行测试（src/test/java/com.lyc.mapper/UserMapperTest）
package com.lyc.mapper;

import com.lyc.pojp.User;
import com.lyc.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {
    @Test
    public void test(){
        //第一步：获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();


        //执行SQL
        //方法1
        UserMapper usermapper = sqlSession.getMapper(UserMapper.class);
        List<User> userlist = usermapper.getUserList();

        //方法2(不推荐)
//        List<User> userlist = sqlSession.selectList("com.lyc.mapper.UserMapper.getUserList");
        for(User user : userlist){
            System.out.println(user);
        }


        //关闭SqlSession
        sqlSession.close();
    }
    @Test
    public void getUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.getUserByID(1);
        System.out.println(user);
        sqlSession.close();
    }
    @Test
    public void adduser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.addUser(new User(4, "jack", "123456"));
        if (res>0){
            System.out.println("插入成功！");
        }
        sqlSession.commit();
        sqlSession.close();

    }
    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        int res = userMapper.updateUser(new User(4, "james", "456123"));
        if (res>0){
        System.out.println("修改成功！");
        }
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.deleteUser(4);
        if (res>0){
            System.out.println("删除成功！");
        }
        sqlSession.commit();
        sqlSession.close();
    }
}