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Mybatis实现基本的增删改查(CRUD)

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导读：本篇文章讲解 Mybatis实现基本的增删改查(CRUD)，希望对大家有帮助，欢迎收藏，转发！站点地址：www.bmabk.com

Mybatis实现基本的增删改查

一、Mybatis是什么？

MyBatis 是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

二、步骤

1.创建项目

  • 新建一个Maven项目，并删除src文件夹，作为父工程
  • 在父工程下新建Maven项目作为子工程
    在这里插入图片描述

2.导入Maven依赖

在父工程的pom.xml文件中导入所需的Maven依赖：

<?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>org.example</groupId>
    <artifactId>MyBatis-Study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>mybatis-01</module>
    </modules>
    <!--导入依赖-->
    <!--mysql驱动-->
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.20</version>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <!--    junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <!--在build中配置resources，来防止我们资源导出失败的问题-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

注：在父工程下创建的所有子工程不需要再次导入这些依赖

3.编写Mybatis核心配置文件

在resources文件夹下新建一个mybatis-config.xml文件

<?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">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mydb1?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="dao/UserMapper.xml"/>
    </mappers>
</configuration>

4.编写Mybatis工具类

在Java文件下新建一个utils文件夹存放MyBatisUtils.java工具类

package utils;
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;
import static org.apache.ibatis.io.Resources.*;
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            //使用Mybatis第一步获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    //从SqlSessionFactory中获取SqlSession
    public static SqlSession getSqlSession() {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }
}

5.编写代码实现CRUD

1. 实体类
在Java文件下新建一个pojo文件夹存放User.java实体类

package pojo;

public class User {
    private int id;
    private String name;
    private String gender;
    private String birthday;

    public User() {
    }

    public User(int id, String name, String gender, String birthday) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.birthday = birthday;
    }

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

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getGender() {
        return gender;
    }

    public String getBirthday() {
        return birthday;
    }

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

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

    public void setGender(String gender) {
        this.gender = gender;
    }

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

2. dao接口
在Java文件夹下新建一个dao文件夹，dao文件夹下新建一个UserMapper接口文件

package dao;

import pojo.User;

import java.util.List;

public interface UserMapper {
    //查询全部用户
    List<User> getUserList();
    //根据ID查询用户
    User getUserById(int id);
    //插入一个用户
    int addUser(User user);
    //根据姓名删除用户
    int delUser(String name);
    //根据id修改用户
    int updUser(User user);
}

3. 接口实现类
在dao文件夹下新建一个UserMapper.xml文件

<?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绑定一个对应的Mapper接口-->
<mapper namespace="dao.UserMapper">
<!--id为对应的namespace中的方法名   resultType为返回值类型 parameterType为参数类型 -->
<!-- 查询全部用户-->
    <select id="getUserList" resultType="pojo.User">
        select * from student;
    </select>
<!--根据ID查询用户-->
    <select id="getUserById" parameterType="int" resultType="pojo.User">
        select * from student where id=#{id}
    </select>
<!--插入用户-->
    <insert id="addUser" parameterType="pojo.User">
        insert into student(id,name,gender,birthday) values(#{id},#{name},#{gender},#{birthday})
    </insert>
<!--删除用户-->
    <delete id="delUser" parameterType="String">
        delete from student where name=#{name}
    </delete>
<!--更新用户-->
    <update id="updUser" parameterType="pojo.User">
        update student set name=#{name},gender=#{gender},birthday=#{birthday} where id=#{id};
    </update>
</mapper>

4. 测试类
Test文件夹下新建UserMapperTest测试类
在这里插入图片描述

package dao;

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

import java.util.List;

public class UserMapperTest {
    @Test
    public void test(){

        //获得SqlSession对象
        SqlSession sqlSession= MybatisUtils.getSqlSession();
        //执行sql
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        List<User> userList=userMapper.getUserList();
        for (User user:userList){
            System.out.println(user);
        }
        sqlSession.close();
    }
    @Test
    public void getUserById(){
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        User user=userMapper.getUserById(1);
        System.out.println(user);
        sqlSession.close();
    }
    @Test
    //增删改需要提交事务
    public void addUser(){
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        int res=userMapper.addUser(new User(10,"杨总","男","1999-10-03"));
        if (res>0){
            System.out.println("插入成功");
        }
        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void delUser(){
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        int res=userMapper.delUser("杨总");
        if (res>0){
            System.out.println("删除成功");
        }
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void updUser(){
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        int res=userMapper.updUser(new User(9,"杨总","男","1999-10-03"));
        if (res>0){
            System.out.println("修改成功");
        }
        sqlSession.commit();
        sqlSession.close();
    }

}

附录

远程仓库地址：
gitee仓库
github仓库

用到的数据库：
在这里插入图片描述
项目结构：
在这里插入图片描述

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