Java Mybatis 增删改查 简单使用 入门 图文版

原文：https://www.cnblogs.com/guxingy/p/13444886.html

1、创建项目

2、引用相关的包

我的idea是打开了自动导入包的，如果没有打开，就需要点一下导入包，一般在右下角会有提示的

打开自动导入包

3、创建包

在java目录上点击右键，添加包

之前有个名字没有改对，现在改一下。把pom.xml里面的org.example改为com.example

接着继续建立包com.example.test1

4、在包com.example.test1下，添加一个类User

package com.example.test1;

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable {
    private int id;
    private String username;// 用户姓名
    private String sex;// 性别
    private Date birthday;// 生日
    private String address;// 地址

    public int getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", sex=" + sex
                + ", birthday=" + birthday + ", address=" + address + "]";
    }

}

5、在resources中，添加日志的配置文件，log4j.properties

添加方法：https://www.cnblogs.com/guxingy/p/13444342.html

代码如下

# Set root category priority to INFO and its only appender to CONSOLE.
#log4j.rootCategory=INFO, CONSOLE            debug   info   warn error fatal
log4j.rootCategory=debug, CONSOLE, LOGFILE

# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE

# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m


# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=d:axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m

6、在resources中，添加数据库的配置文件，SqlMapConfig.xml

添加方法：https://www.cnblogs.com/guxingy/p/13444274.html

代码如下

<?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>

    <!--   配置环境-->
    <environments default="mysql">
        <!--配置mysql的环境-->
        <environment id="mysql">
            <!--配置事务的类型-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置连接池-->
            <dataSource type="POOLED">
                <!--配置连接数据库的4个基本信息-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    
    <!--指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件-->
    <mappers>
        <mapper resource="User.xml"/>
    </mappers>

</configuration>

7、在resources中，添加映射文件，User.xml

这个映射文件，里面大部分是些sql语句，只是把实体的属性插入到了sql语句中。相当于sql语句是个模板引擎，只是对里面的字符串做了一个替换而已。

添加方法：https://www.cnblogs.com/guxingy/p/13444381.html

代码如下

<?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：用来区别不同的类的名字 -->
<mapper namespace="User">

    <!-- 通过Id查询一个用户   -->
    <select id="findUserById" parameterType="Integer" resultType="com.example.test1.User">
        select * from user where id = #{v}
    </select>

    <!-- 根据用户名模糊查询用户列表 -->
    <select id="findUserByUsername" parameterType="String" resultType="com.example.test1.User">
        select * from user where username like CONCAT('%',#{username},'%')
    </select>

    <!--  添加用户  -->
    <insert id="insertUser" parameterType="com.example.test1.User">
        <selectKey keyProperty="id" resultType="Integer" order="AFTER">
            select LAST_INSERT_ID()
        </selectKey>
        insert into user (username,birthday,address,sex) values(#{username},#{birthday},#{address},#{sex})
    </insert>

    <!-- 更新用户 -->
    <update id="updateUserById" parameterType="com.example.test1.User">
		update user
		set username = #{username},sex = #{sex},birthday = #{birthday},address = #{address}
		where id = #{id}
	</update>

    <!-- 删除用户   -->
    <delete id="deleteUserById" parameterType="Integer">
		delete from user
		where id = #{vvvvv}
	</delete>

</mapper>

8、添加测试文件，MybatisTest.java

import com.example.test1.User;

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 org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;

/**
 * @ClassName: MybatisTest
 * @author: benjamin
 * @version: 1.0
 * @description: TODO
 * @createTime: 2019/07/13/11:50
 */

public class MybatisTest {
    public static void main(String[] args) {

    }

    //通过Id查询一个用户
    @Test
    public void testSearchById() throws IOException {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //3.使用工厂生产SqlSession对象
        SqlSession session = sqlSessionFactory.openSession();
        //4.执行Sql语句
        User user = session.selectOne("User.findUserById", 1);
        //5. 打印结果
        System.out.println(user);
        //6.释放资源
        session.close();
        in.close();
    }

    //根据用户名模糊查询用户列表
    @Test
    public void testFindUserByUsername() throws IOException {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //3.使用工厂生产SqlSession对象
        SqlSession session = sqlSessionFactory.openSession();
        //4.执行Sql语句
        List<User> list = session.selectList("User.findUserByUsername", "测试");
        //5. 打印结果
        for (User user:list) {
            System.out.println(user);
        }
        //6.释放资源
        session.close();
        in.close();
    }

    //添加用户
    @Test
    public void testInsertUser() throws IOException {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //3.使用工厂生产SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //4.执行Sql语句
        User user = new User();
        user.setUsername("小强");
        user.setBirthday(new Date());
        user.setAddress("广州");
        user.setSex("男");
        int i = sqlSession.insert("User.insertUser", user);
        sqlSession.commit();
        //5. 打印结果
        // 刚保存用户，此时用户ID需要返回。执行完上面insert程序后，此时就能知道用户的ID是多少
        // 需要在User.xml文件中配置
        System.out.println("插入id:"+user.getId());//插入id:30

        //6.释放资源
        sqlSession.close();
        in.close();
    }

    //更新用户
    @Test
    public void testUpdateUserById() throws IOException {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //3.使用工厂生产SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //4.执行Sql语句
        User user = new User();
        user.setId(3);
        user.setUsername("小李");
        user.setBirthday(new Date());
        user.setAddress("深圳");
        user.setSex("女");
        int i = sqlSession.insert("User.updateUserById", user);
        sqlSession.commit();
        //5. 打印结果
        System.out.println(user.getId());
        //6.释放资源
        sqlSession.close();
        in.close();
    }

    //删除用户
    @Test
    public void testDeleteUserById() throws IOException {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //3.使用工厂生产SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //4.执行Sql语句
        int i = sqlSession.insert("User.deleteUserById", 3);
        sqlSession.commit();
        //5. 打印结果
        System.out.println(i);
        //6.释放资源
        sqlSession.close();
        in.close();
    }
}

9、添加数据库和测试数据

数据库对应的表

初始数据

10、测试

先编译一下项目，没有导入包，还是要导入一下哈，没有报错即可。

11、源码和数据库脚本

https://files-cdn.cnblogs.com/files/guxingy/Mybatis-增删改查.rar

12、GitHub地址

https://github.com/guxingy/MyBatis-Example

13、总结

第一次使用后的感觉，其核心还是在User.xml，里面配置了SQL语句，
这里SQL语句注入的参数和Model的属性对应，这里的SQL语句相当于是个模板，感觉就有点像dapper那种