MyBatis学习笔记一

本文最后更新于：3 个月前

本文主要记录了Java中的MyBatis框架的学习，初次了解其在项目中的具体位置和功能。

MyBatis

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什么是 MyBatis？

MyBatis 是一款持久层框架，

它支持自定义 SQL、存储过程以及高级映射。

安装

要使用 MyBatis， 只需将 mybatis-x.x.x.jar 文件置于类路径（classpath）中即可。

如果使用 Maven 来构建项目，则需将下面的依赖代码置于 pom.xml 文件中：

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<dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis</artifactId>
  <version>3.5.7</version>
</dependency>

我学习时的配置:

  • MySQL5.7
  • Maven3.6.0
  • Mybatis3.5.2
  • IDEA2019.1

我学习时的父工程pom.xml文档

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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    
    <!--  父工程 -->
    <groupId>com.zmq</groupId>
    <artifactId>Mybatis-Study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>mybatis-01</module>
    </modules>

    <!-- 依赖  -->
    <dependencies>
<!--        MySQL驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
<!--        mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
<!--        junit测试单元框架-->
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
<!--    资源过滤，防止运行时找不到文件-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>

</project>

子工程pom.xml文档

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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>Mybatis-Study</artifactId>
        <groupId>com.zmq</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>mybatis-01</artifactId>

	<!--    资源过滤，防止运行时找不到文件-->
    <build>
        <resources>
            <resource>
    			<directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>

</project>

创建MyBatis配置文件

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<!-- mybatis-config.xml -->

<?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">

<!--核心配置文件-->
<configuration>
    <environments default="development">
        <environment id="development">
<!--            事务管理-->
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3307/mydb?useUnicode=true&amp;characterEncoding=utf8&amp;autoReconnect=true&amp;useSSL=false&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

<!--    创建接口后注册接口实现文件-->
    <mappers>
        <mapper resource="com/zmq/dao/UserMapper.xml"/>
    </mappers>


</configuration>


创建工具类

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//MybatisUtils.java
package com.zmq.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SqlSession对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //SqlSession 完全包含了面向数据库执行SQL命令的所有方法
    public static SqlSession getSqlSession(){
        //openSession(true)可以自动提交事务
        return sqlSessionFactory.openSession();
    }


}

创建Pojo层实体类

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//User.java
package com.zmq.pojo;

public class User {
    private int id;
    private String name;
    private String pwd;

    //无参构造
    public User() {
    }
    //有参构造
    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }
    //getset方法
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    //toString方法
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

创建接口文件(Dao层)

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//UserDao.java
package com.zmq.dao;

import com.zmq.pojo.User;

import java.util.List;

public interface UserDao {

    //获取所有用户
    List<User> getUserList();

    //根据id查询用户
    User getUserById(int id);

    //新增用户
    int addUser(User user);

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

    //删除用户
    int delUserById(int id);


}

创建接口实现配置文件(相当于JavaWeb的impl层)

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<!-- UserMapper.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">
<!--namespace用来绑定DAO接口-->
<mapper namespace="com.zmq.dao.UserDao">
<!--    这里相当于实现接口的方法    resultType绑定全限定名-->
    <select id="getUserList" resultType="com.zmq.pojo.User">
        select * from mydb.user
    </select>

    <select id="getUserById" parameterType="int" resultType="com.zmq.pojo.User">
        select * from mydb.user where id = #{id}
    </select>

    <insert id="addUser" parameterType="com.zmq.pojo.User" >
        insert into mydb.user(id, name, pwd) values (#{id},#{name},#{pwd});
    </insert>

    <update id="updateUser" parameterType="com.zmq.pojo.User">
        update mydb.user set name=#{name},pwd=#{pwd} where id = #{id}
    </update>

    <delete id="delUserById" parameterType="int">
        delete from mydb.user where id = #{id}
    </delete>
</mapper>

测试

在Dao的文件中，右击要测试的方法，点击goto，创建测试

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//UserDaoTest.java
package com.zmq.dao;

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

import java.util.List;


public class UserDaoTest {

    //测试查询全部User
    @Test
    public void test(){
        //获取sqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //sqlSession.getMapper(UserDao.class);后ALT+回车生成赋给的对象UserDao
        //这里要拿SQL，从Dao包里拿，面向接口编程，可以直接从UserDao接口里拿
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        //执行方法
        List<User> userList = userDao.getUserList();

        //增强For循环输出
        for(User user:userList){
            System.out.println(user);
        }


        //关闭sqlSession
        sqlSession.close();
    }

    //测试通过id查询
    @Test
    public void getUserById(){
        //获取sqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao userDao = sqlSession.getMapper(UserDao.class);

        User user = userDao.getUserById(1);
        System.out.println(user);

        //关闭sqlSession
        sqlSession.close();
    }


    //测试新增用户
    @Test
    public void addUser(){
        //获取sqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao userDao = sqlSession.getMapper(UserDao.class);

        userDao.addUser(new User(3,"alan","852456"));

        //提交事务----->>增删改都要提交事务，否则保存不到数据库
        sqlSession.commit();
        System.out.println("添加成功！");
        //关闭sqlSession
        sqlSession.close();
    }

    //测试修改用户
    @Test
    public void updateUser(){
        //获取sqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao userDao = sqlSession.getMapper(UserDao.class);

        userDao.updateUser(new User(2,"alex","159852"));


        //提交事务----->>增删改都要提交事务，否则保存不到数据库
        sqlSession.commit();
        System.out.println("修改成功！");
        //关闭sqlSession
        sqlSession.close();
    }


    //测试删除用户
    @Test
    public void delUserById(){
        //获取sqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao userDao = sqlSession.getMapper(UserDao.class);

        userDao.delUserById(2);


        //提交事务----->>增删改都要提交事务，否则保存不到数据库
        sqlSession.commit();
        System.out.println("删除成功！");
        //关闭sqlSession
        sqlSession.close();
    }


}
笔记
#Java #Mybatis
MyBatis学习笔记一
https://superlovelace.top/2023/10/24/MyBatis_1/
作者
棱境
发布于
2023年10月24日
更新于
2023年10月31日
许可协议