IDEA+Maven使用MyBatis实现CRUD操作

Hello，大家好，今天我为大家带来在IDEA中使用Maven构建MyBatis项目，实现简单的增删改查操作，

总结了博主在学习过程中的一些经验，下面进入构建项目

MyBatis介绍

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。

​ —> 摘自MyBatis官网

为什么使用MyBatis

首先，之前用的是JDBC实现数据库的CRUD操作，拼接SQL语句过于麻烦，代码容易出错，大大降低开发效率

使用MyBatis实现CRUD操作大大提升了开发效率，MyBatis作为一款优秀的持久层框架，大大减少了SQL语句的拼接，提升了代码的易读性，便于维护，利用MyBatis采用接口对应XML文件的方式来实现对数据库的CRUD操作。

新建Maven项目

File --> New —> Project

如下：

单击Next

单击Finish完成Maven项目创建

==注意：Maven构建项目时需要看Maven指向的路径是不是本地路径==

File --> setting --> Build,Exception,Eeployment --> Build Tools --> Maven

配置完后，单击Apply同意，OK确认

配置pom.xml文件

<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>3.5.4</version>
        </dependency>
<!--        junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
            </resource>
            <resource>
                <directory>libs/</directory>
                <targetPath>libs</targetPath>
                <includes>
                    <include>**/*.jar</include>
                </includes>
            </resource>
        </resources>
    </build>

项目结构

数据库准备

新建数据库mybatis ，数据表user

CREATE DATABASE mybatis;
USE mybatis;
CREATE TABLE `user` (
  `id` int(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(30) DEFAULT NULL,
  `password` varchar(30) DEFAULT NULL,
  PRIMARY KEY (`id`)
)

resources —> New —> File 命名为db.properties配置数据库信息

db.properties文件

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1/mybatis?useSSL=true
username=root
password=111111

MyBatis核心配置文件

resources —> New —> File 命名为mybatis-config.xml

==注意：单击刷新键，将配置的文件从远程仓库下载到本地仓库中==

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">
<configuration>

<!--    引入数据库配置信息-->
    <properties resource="db.properties"/>
    <settings>
        <!--        标准的日志工厂实现-->
        <setting name="logImpl" value="StDOUT_LOGGING"/>
        <!--        <setting name="logImpl" value="LOG4J"/>-->
    </settings>
    <typeAliases>
        <package name="com.wanshi.bean"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driverClassName}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--    注册接口-->
    <mappers>
        <mapper resource="com/wanshi/mapper/UserMapper.xml"></mapper>
    </mappers>
</configuration>

编写源代码

新建如下项目结构

MyBatis工具类

编写MyBatisUtils类

package com.wanshi.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 {
            String resources = "mybatis-config.xml";
            //将mybatis核心配置文件封装成输入流
            InputStream in = Resources.getResourceAsStream(resources);
            //SqlSessionFactoryBuilder对输入流进行build编译为sqlSessionFactory
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * sqlSessionFactory构造返回一个SqlSession进行数据库CRUD操作
     * @return
     */
    public SqlSession getSession() {
        return sqlSessionFactory.openSession();
    }
}

实体类

编写User类

package com.wanshi.bean;

public class User {

    private Integer id;
    private String name;
    private Integer password;

    public User() {
    }

    public User(Integer id, String name, Integer password) {
        this.id = id;
        this.name = name;
        this.password = password;
    }

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public Integer getPassword() {
        return password;
    }

    public void setPassword(Integer password) {
        this.password = password;
    }

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

mapper接口与xml文件编写

编写UserMapper接口

package com.wanshi.mapper;

import com.wanshi.bean.User;
import org.apache.ibatis.annotations.Param;

import java.util.List;

public interface UserMapper {

    /**
     * 查询所有的用户
     * @return
     */
    List<User> getUserList();

    /**
     * 根据用户id查询一个用户信息
     * @param id
     * @return
     */
    User getByUserId(@Param("uid") Integer id);

    /**
     * 增加一个用户
     * @param user
     * @return
     */
    Integer add(User user);

    /**
     * 修改一个用户信息
     * @param user
     * @return
     */
    Integer update(User user);

    /**
     * 根据用户id删除一个用户
     * @param id
     * @return
     */
    Integer delete(@Param("uid") Integer id);
}

UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wanshi.mapper.UserMapper">

    <select id="getUserList" resultType="user">
        select * from user
    </select>

    <select id="getByUserId" resultType="user">
        select * from user where id = #{uid}
    </select>

    <insert id="insert" parameterType="user">
        insert into user (name, password) values(#{name}, #{password})
    </insert>

    <update id="update" parameterType="user">
        update user set name = #{name}, password = #{password} where id = #{id}
    </update>

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

IDEA中连接数据库

单击右侧DataSource选项连接数据库

单击+

选择DataSource — > MySQL

单击apply同意，单击ok，连接成功，如下页面

测试

新建测试类,TestUser，这里利用Junit单元测试来实现

package com.wanshi.test;

import com.wanshi.bean.User;
import com.wanshi.mapper.UserMapper;
import com.wanshi.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class TestUser {

    @Test
    public void getUserList() {
        SqlSession sqlSession = MyBatisUtils.getSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = userMapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }

    @Test
    public void getByUserId() {
        SqlSession sqlSession = MyBatisUtils.getSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.getByUserId(1);
        System.out.println(user);
        sqlSession.close();
    }

    @Test
    public void insert() {
        SqlSession sqlSession = MyBatisUtils.getSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = new User();
        user.setName("admin");
        user.setPassword(1234);
        Integer i = userMapper.insert(user);
        System.out.println(i);
        //    注意：增删改操作需要手动开启事务，否则无法执行
        if (i > 0) {
            sqlSession.commit();
        }
        sqlSession.close();
        
    }

    @Test
    public void update() {
        SqlSession sqlSession = MyBatisUtils.getSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        Integer i = userMapper.update(new User(3, "李三", 123445));
        System.out.println(i);
        //    注意：增删改操作需要手动开启事务，否则无法执行
        if (i > 0) {
            sqlSession.commit();
        }
        sqlSession.close();
    }

    @Test
    public void delete() {
        SqlSession sqlSession = MyBatisUtils.getSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        Integer i = userMapper.delete(2);
        System.out.println(i);
        //    注意：增删改操作需要手动开启事务，否则无法执行
        if (i > 0) {
            sqlSession.commit();
        }
        sqlSession.close();
    }

}

测试结果

查询所有用户

根据用户id查询指定用户

增加用户

修改用户

删除用户

结语

MyBatis入门级的增删改查操作就结束了，程序执行肯定没问题，遇到问题的小伙伴可在评论区留言，我们下篇见，Mybatis系列文章！