Mybatis中的CRUD操作

Mybatis的CRUD操作

我们在创建第一个项目自后，来进行数据库的操作；

Mybatis在JDBC的基础上，对sql语句的执行进行了简化。

1.准备工作

1.1.创建我们的第二个项目，项目结构如下：

image-20210411210657493

1.2.在pom.xml文件中引入资源文件导出的配置文件

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

2.编写我们需要测试的代码

2.1 select标签

  • 在dao包下编写UserMapper接口的接口方法
package com.xiaoli.dao;

import com.xiaoli.pojo.User;

import java.util.List;

public interface UserMapper {

    //查询所有的用户
    public List<User> getUser();

    //条件查询
    public User getUserById(int id);

}

  • 在UserMapper.xml文件中编写sql语句

    <?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 namespace="com.xiaoli.dao.UserMapper">
    <!--查询全部用户-->
    <select id="getUser" resultType="User">
        select * from mybatis.user
    </select>
    <!--条件查询-->
    <!--
        select id=""：方法名
        parameterType=""：传入的参数类型
        resultType=""：返回值类型
    -->
    <select id="getUserById" parameterType="int" resultType="com.xiaoli.pojo.User">
        select * from mybatis.user where id = #{id}
    </select>
</mapper>

  • 测试代码与结果：

    //获取所有的用户
    @Test
    public void testGetUser(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();

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

        List<User> user = mapper.getUser();

        System.out.println("查询全部用户");
        for (User user1 : user) {
            System.out.println(user1);
        }

        sqlSession.close();
    }

    //条件查询
    @Test
    public void testGetUserById(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();

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

        System.out.println("条件查询");
        User userById = mapper.getUserById(3);
        System.out.println(userById);
        
        sqlSession.close();
    }

    测试结果：

    全部查询

    image-20210411221933610

    条件查询：

    image-20210411222043484

2.2 insert标签

  • 在dao包下编写UserMapper接口的接口方法
package com.xiaoli.dao;

import com.xiaoli.pojo.User;

import java.util.List;

public interface UserMapper {

    //向数据库中插入数据
    public int insertUser(User user);

}

  • 在UserMapper.xml文件中编写sql语句

    <?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 namespace="com.xiaoli.dao.UserMapper">
    <!--插入数据-->
    <insert id="insertUser" parameterType="com.xiaoli.pojo.User">
        insert into mybatis.user(id,username,password) values(#{id},#{username},#{password})
    </insert>
</mapper>

  • 测试代码与结果：

    注意：在做增删改操作时，需要进行事务提交

    package com.xiaoli.dao;

import com.xiaoli.pojo.User;
import com.xiaoli.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {

    //插入操作
    //在做增删改操作时，需要进行事务提交
    @Test
    public void testInsertUser(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();

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

        System.out.println("插入数据");
        int i = mapper.insertUser(new User(8, "小虎", "27813"));

        System.out.println(i);

        //事务提交
        sqlSession.commit();
        sqlSession.close();
    }
}

    测试结果：

    image-20210411223342140

    image-20210411223519360

2.3 update标签

  • 在dao包下编写UserMapper接口的接口方法
package com.xiaoli.dao;

import com.xiaoli.pojo.User;

import java.util.List;

public interface UserMapper {

    //更新数据库中的数据
    public int updateUserById(User user);

}

  • 在UserMapper.xml文件中编写sql语句

    <?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 namespace="com.xiaoli.dao.UserMapper">
    <!--更新数据-->
    <!--
        我们更新我们刚才插入的数据：8, "小虎", "27813" 更新为 8, “小花”，“34233”
    -->
    <update id="updateUserById" parameterType="com.xiaoli.pojo.User">
        update mybatis.user set username = #{username},password = #{password} where id = #{id}
    </update>
</mapper>

  • 测试代码与结果：

    注意：在做增删改操作时，需要进行事务提交

    package com.xiaoli.dao;

import com.xiaoli.pojo.User;
import com.xiaoli.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {

	//更新操作
    //在做增删改操作时，需要进行事务提交
    @Test
    public void testUpdateUserById(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();

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

        System.out.println("更新数据");
        //"小虎", "27813" 更新为 8, “小花”，“34233”
        int i = mapper.updateUserById(new User(8, "小花", "34233"));

        System.out.println(i);

        //事务提交
        sqlSession.commit();
        sqlSession.close();
    }
}

    测试结果：

    image-20210411224502538

    image-20210411224548097

2.4 delete标签

  • 在dao包下编写UserMapper接口的接口方法
package com.xiaoli.dao;

import com.xiaoli.pojo.User;

import java.util.List;

public interface UserMapper {

    //通过指定的Id删除用户
    public int deleteUserById(int id);

}

  • 在UserMapper.xml文件中编写sql语句

    <?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 namespace="com.xiaoli.dao.UserMapper">
    <!--删除数据-->
    <!--
        例子：我们删除刚才插入的数据：id = 8
    -->
    <delete id="deleteUserById" parameterType="int">
        delete from mybatis.user where id = #{id}
    </delete>
</mapper>

  • 测试代码与结果：

    注意：在做增删改操作时，需要进行事务提交

    package com.xiaoli.dao;

import com.xiaoli.pojo.User;
import com.xiaoli.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {

    //删除操作
    //在做增删改操作时，需要进行事务提交
    @Test
    public void testDeleteUserById(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();

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

        System.out.println("删除数据");
        //删除id = 8的用户
        int i = mapper.deleteUserById(8);

        System.out.println(i);

        //事务提交
        sqlSession.commit();
        sqlSession.close();
    }
}

    测试结果：

    image-20210411225233628

    image-20210411225318067

posted on 2021-04-11 22:55  Code_xiaoli  阅读(104)  评论(0)    收藏  举报



Live2D