02.CRUD 初体验

1.MyBatisUtil 工具类

java

package org.hong.util;

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 MyBatisUtil {

    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
    public static SqlSession getSqlSession(){
        // openSession(): 此方式打开SQL会话, 事务是开启状态
        // openSession(true): 此方式打开SQL会话, 事务是关闭状态
        return sqlSessionFactory.openSession();
    }

    public static SqlSessionFactory getSqlSessionFactory() {
        return sqlSessionFactory;
    }
}

2.save

接口方法

java

// 保存
int save(User user);

方法映射

xml

<!--
    inserte: 配置insert语句
        id: 对应的方法名
        parameterType: 指定参数类型为pojo, 可以直接写属性名获得属性值, 优先调用getting方法, 如果没有getting方法则直接从属性中取值
 -->
<insert id="save" parameterType="org.hong.pojo.User">
    insert into user(name, pwd) values(#{name}, #{pwd})
</insert>

测试用例

java

@Test
public void save(){
    // 1.获取sqlSession对象
    SqlSession sqlSession = MyBatisUtil.getSqlSession();
    // 2.获取需要的mapper接口的代理对象
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    // 3.调用对应的方法执行操作
    User user = new User();
    user.setName("SAVE");
    user.setPwd("123");
    int save = mapper.save(user);
    System.out.println(save);
    System.out.println(user);
    // 4.提交事务
    sqlSession.commit();
    // 5.关闭sqlSession
    sqlSession.close();
}

控制台打印

shell

## 发送的sql语句
[main] [org.hong.mapper.UserMapper.save]-[DEBUG] ==>  Preparing: insert into user(name, pwd) values(?, ?)
## 预编译放入的参数值, 从传入的pojo对象中取出对应的属性值
[main] [org.hong.mapper.UserMapper.save]-[DEBUG] ==> Parameters: SAVE(String), 123(String)
## 影响行数
[main] [org.hong.mapper.UserMapper.save]-[DEBUG] <==    Updates: 1
## 编写的save方法返回的值int类型, 意义是数据库影响行数
1
## 插入后的对象打印, id值并没有回填到对象中, 因为我们没有开启这个功能, 后面会说到
User(id=null, name=SAVE, pwd=123)

3.get

接口方法

java

// 根据id查询
User get(int id);

方法映射

xml

<!-- 方法参数是int类型的, 所以没有写parameterType属性 -->
<select id="get" resultType="org.hong.pojo.User">
    <!-- 插入id值 -->
    select * from user where id = #{id}
</select>

测试用例

java

@Test
public void get(){
    // 1.获取sqlSession对象
    SqlSession sqlSession = MyBatisUtil.getSqlSession();
    // 2.获取需要的mapper接口的代理对象
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    // 3.调用对应的方法执行操作
    User user = mapper.get(1);
    System.out.println(user);
    // 4.提交事务
    sqlSession.commit();
    // 5.关闭sqlSession
    sqlSession.close();
}

控制台打印

shell

[main] [org.hong.mapper.UserMapper.get]-[DEBUG] ==>  Preparing: select * from user where id = ?
[main] [org.hong.mapper.UserMapper.get]-[DEBUG] ==> Parameters: 1(Integer)
[main] [org.hong.mapper.UserMapper.get]-[DEBUG] <==      Total: 1
User(id=1, name=hong, pwd=123456)

4.update

接口方法

java

// 修改
int update(User user);

方法映射

xml

<update id="update" parameterType="org.hong.pojo.User">
    update user set name = #{name}, pwd = #{pwd} where id = #{id}
</update>

测试用例

java

@Test
public void update(){
    // 1.获取sqlSession对象
    SqlSession sqlSession = MyBatisUtil.getSqlSession();
    // 2.获取需要的mapper接口的代理对象
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    // 3.调用对应的方法执行操作
    User user = mapper.get(1);
    user.setName("谢禹宏");
    int update = mapper.update(user);
    System.out.println(user);
    // 4.提交事务
    sqlSession.commit();
    // 5.关闭sqlSession
    sqlSession.close();
}

控制台打印

shell

## 查询sql
[main] [org.hong.mapper.UserMapper.get]-[DEBUG] ==>  Preparing: select * from user where id = ?
[main] [org.hong.mapper.UserMapper.get]-[DEBUG] ==> Parameters: 1(Integer)
[main] [org.hong.mapper.UserMapper.get]-[DEBUG] <==      Total: 1
## 修改sql
[main] [org.hong.mapper.UserMapper.update]-[DEBUG] ==>  Preparing: update user set name = ?, pwd = ? where id = ?
[main] [org.hong.mapper.UserMapper.update]-[DEBUG] ==> Parameters: 谢禹宏(String), 123456(String), 1(Integer)
[main] [org.hong.mapper.UserMapper.update]-[DEBUG] <==    Updates: 1
User(id=1, name=谢禹宏, pwd=123456)

5.delete

接口方法

java

// 删除
boolean delete(int id);

方法映射

xml

<delete id="delete">
    delete from user where id = #{id}
</delete>

测试用例

java

@Test
public void delete(){
    // 1.获取sqlSession对象
    SqlSession sqlSession = MyBatisUtil.getSqlSession();
    // 2.获取需要的mapper接口的代理对象
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    // 3.调用对应的方法执行操作
    boolean delete = mapper.delete(10);
    System.out.println(delete);
    // 4.提交事务
    sqlSession.commit();
    // 5.关闭sqlSession
    sqlSession.close();
}

控制台打印

shell

[main] [org.hong.mapper.UserMapper.delete]-[DEBUG] ==>  Preparing: delete from user where id = ?
[main] [org.hong.mapper.UserMapper.delete]-[DEBUG] ==> Parameters: 10(Integer)
[main] [org.hong.mapper.UserMapper.delete]-[DEBUG] <==    Updates: 0
## 因为我们删除一个不存在的数据, 影响行数为0, 所以MyBatis返回false
false

6.最终版

6.1 Mapper 接口

java

package org.hong.mapper;

import org.hong.pojo.User;


public interface UserMapper {
    // 保存
    int save(User user);

    // 根据id查询
    User get(int id);

    // 修改
    int update(User user);

    // 删除
    boolean delete(int id);
}

6.2 Mapper.xml

xml

<?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="org.hong.mapper.UserMapper">

    <!--
        inserte: 配置insert语句
            id: 对应的方法名
            parameterType: 指定参数类型为pojo, 可以直接写属性名获得属性值, 优先调用getting方法, 如果没有getting方法则直接从属性中取值
     -->
    <insert id="save" parameterType="org.hong.pojo.User">
        insert into user(name, pwd) values(#{name}, #{pwd})
    </insert>
    <!-- 方法参数是int类型的, 所以没有写parameterType属性 -->
    <select id="get" resultType="org.hong.pojo.User">
        <!-- 插入id值 -->
        select * from user where id = #{id}
    </select>
    <update id="update" parameterType="org.hong.pojo.User">
        update user set name = #{name}, pwd = #{pwd} where id = #{id}
    </update>
    <delete id="delete">
        delete from user where id = #{id}
    </delete>
</mapper>

6.3 测试用例

java

package org.hong.test;

import org.apache.ibatis.session.SqlSession;
import org.hong.mapper.UserMapper;
import org.hong.pojo.User;
import org.hong.util.MyBatisUtil;
import org.junit.Test;

public class CRUDTest {
    @Test
    public void save(){
        // 1.获取sqlSession对象
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        // 2.获取需要的mapper接口的代理对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        // 3.调用对应的方法执行操作
        User user = new User();
        user.setName("SAVE ID");
        user.setPwd("123");
        int save = mapper.save(user);
        System.out.println(save);
        System.out.println(user);
        // 4.提交事务
        sqlSession.commit();
        // 5.关闭sqlSession
        sqlSession.close();
    }

    @Test
    public void get(){
        // 1.获取sqlSession对象
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        // 2.获取需要的mapper接口的代理对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        // 3.调用对应的方法执行操作
        User user = mapper.get(1);
        System.out.println(user);
        // 4.提交事务
        sqlSession.commit();
        // 5.关闭sqlSession
        sqlSession.close();
    }

    @Test
    public void update(){
        // 1.获取sqlSession对象
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        // 2.获取需要的mapper接口的代理对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        // 3.调用对应的方法执行操作
        User user = mapper.get(1);
        user.setName("谢禹宏");
        int update = mapper.update(user);
        System.out.println(user);
        // 4.提交事务
        sqlSession.commit();
        // 5.关闭sqlSession
        sqlSession.close();
    }

    @Test
    public void delete(){
        // 1.获取sqlSession对象
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        // 2.获取需要的mapper接口的代理对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        // 3.调用对应的方法执行操作
        boolean delete = mapper.delete(10);
        System.out.println(delete);
        // 4.提交事务
        sqlSession.commit();
        // 5.关闭sqlSession
        sqlSession.close();
    }
}

02.CRUD 初体验 ​

1.MyBatisUtil 工具类 ​

2.save ​

3.get ​

4.update ​

5.delete ​

6.最终版 ​

6.1 Mapper 接口 ​

6.2 Mapper.xml ​

6.3 测试用例 ​

02.CRUD 初体验

1.MyBatisUtil 工具类

2.save

3.get

4.update

5.delete

6.最终版

6.1 Mapper 接口

6.2 Mapper.xml

6.3 测试用例