MyBatis-使用注释方法执行操作案例-2023-04-18

第一步：编写工具类，注意openSession 参数如增加true ,则为事务自动提交

package com.feijian.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;

//sqlSessionFactory
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;

    static{
        try {
            //第一步，获取sqlSessionFactory 对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            //sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 有了sqlSessionFactory ,可以获得sqlSession实例,如果在opensession中增加true，意味着事务自动提交
  public static SqlSession getSqlSession(){
      return sqlSessionFactory.openSession(true);
  }

}

第二步：编写核心配置文件 ，采用注释则注册的mapper 就是接口类了 class ,而不是resource

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<!--configuration 核心配置文件 -->
<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?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
<mappers>
    <mapper class="com.feijian.mapper.UserMapper"/>
</mappers>
</configuration>

第三步：编写接口类，并增加注解内容，实际上就是将之前UserMapper.xml的内容，写入到@Select @Update @Insert @Delete 等注释语句中

package com.feijian.mapper;

import com.feijian.pojo.User;
import org.apache.ibatis.annotations.*;

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

public interface UserMapper {
    //获取全部用户
    @Select("select * from mybatis.user;")
    List<User> getUserList() ;

    //根据ID查询用户
    @Select("select * from mybatis.user where id = #{uid};")
    User getUserById(@Param("uid") int id);

    //insert一个新用户,影响的行数，所以返回boolean类型，true说明插入成功，一般不会反馈1表示插入成功！
    @Insert("insert into mybatis.user(id,name,pwd) values (#{id},#{name},#{pwd})")
    boolean addUser(User user);

    //修改用户 修改的行数
    @Update("update mybatis.user set name=#{name},pwd=#{pwd} where id=#{id};")
    boolean updateUser(User user);

    //删除用户
    @Delete("delete from mybatis.user where id = #{id};")
    boolean deleteUser(int id);
}

第四步：在核心配置文件中注册接口类 mapper  ---已注册，注意是class

<mappers>
    <mapper class="com.feijian.mapper.UserMapper"/>
</mappers>

第五步：调试, 一定要记住最后要关闭资源，close(), close(),close() 重要的事情强调三遍！！！

package com.feijian.mapper;

import com.feijian.pojo.User;
import com.feijian.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {
    //查询所有客户
    @Test
    public void test1(){
        //获得sqlsession
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //找到UserMapper类并生成mapper对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //调用接口类中的方法，查询所有用户
        List<User> userList = mapper.getUserList();
        //遍历打印输出
        for (User user : userList) {
            System.out.println(user);
        }
        //关闭资源
        sqlSession.close();
    }

    //根据ID查询
    @Test
    public void test2(){
        //获得sqlsession
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //找到UserMapper类并生成mapper对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //调用接口类中的方法，查询所有用户
        User user = mapper.getUserById(3);
        //遍历打印输出
        System.out.println(user);
        //关闭资源
        sqlSession.close();
    }

    //增加一个新用户
    @Test
    public void test3(){
        //获得sqlsession
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //找到UserMapper类并生成mapper对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //调用接口类中的方法，查询所有用户
        boolean flag =mapper.addUser(new User(6,"jun","230418"));
        //遍历打印输出
        System.out.println(flag);
        System.out.println("增加新用户成功！");
        //关闭资源
        sqlSession.close();
    }

    //修改一个用户
    @Test
    public void test4(){
        //获得sqlsession
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //找到UserMapper类并生成mapper对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //调用接口类中的方法，查询所有用户
        boolean flag =mapper.updateUser(new User(5,"liu","1234567"));
        //遍历打印输出
        System.out.println(flag);
        System.out.println("用户修改成功！");
        //关闭资源
        sqlSession.close();
    }

    //删除一个用户
    @Test
    public void test5(){
        //获得sqlsession
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //找到UserMapper类并生成mapper对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //调用接口类中的方法，查询所有用户
        boolean flag =mapper.deleteUser(9);
        //遍历打印输出
        System.out.println(flag);
        System.out.println("用户删除成功！");
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        //关闭资源
        sqlSession.close();
    }
}