MyBatis 框架之快速入门程序

Posted 2020-11-02 compassblog

一、使用 IDEA 快速创建 Maven 项目

关于如何快速创建 Maven 项目，这个可以参考下面这篇文章：

Maven 项目管理工具基础入门系列（一）

二、快速配置 MyBatis 依赖 jar 包

打开 pom.xml 文件，快速配置 jar 包，配置代码如下：

<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.mybatis</groupId>
  <artifactId>MyBatisDemo</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>MyBatisDemo Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>

    <!-- MyBatis 依赖包 -->
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.4.5</version>
    </dependency>

    <!-- 数据库驱动依赖包 -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.25</version>
    </dependency>

    <!-- junit 测试依赖包 -->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    
  </dependencies>

  <build>
    <finalName>MyBatisDemo</finalName>
    <resources>
      <resource>
        <directory>src/main/java</directory>
        <includes>
          <include>**/*.xml</include>
        </includes>
        <filtering>true</filtering>
      </resource>
    </resources>
  </build>

</project>

三、快速创建实体类

创建 pojo 类 User.java，代码如下：

package com.mybatis.pojo;

public class User{

    private int id;
    private String username;
    private String password;
    private int age;

    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 getPassword() {
        return password;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
    
    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", password="
                + password + ", age=" + age + "]";
    }
    
}

四、快速创建实体类对应的数据表

新建数据库 mybatis_db，创建表 t_user，建表代码如下：

CREATE TABLE `t_user`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `password` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT ‘‘,
  `age` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 2 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

五、快速创建 Mapper 接口

创建接口 UserDao.java，代码如下：

package com.mybatis.dao;

import com.mybatis.pojo.User;

public interface UserDAO {
    
    //新增用户
    public int addUser(User user);
    
    //根据id删除用户
    public int deleteUser(int id);
    
    //修改用户
    public int updateUser(User user);
    
    //根据id查询用户
    public User selectUserById(int id);
    
}

六、快速创建 Mapper 接口代理文件

创建 xml 文件 UserDaoMapper.java，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"> 

<mapper namespace="com.mybatis.dao.UserDao">
     
    <insert id="addUser" parameterType="com.mybatis.pojo.User">
       insert into t_user (username,password,age) values (#{username},#{password},#{age})
    </insert>
    
    <delete id="deleteUser" parameterType="int">
       delete from t_user where id=#{id}  
    </delete> 
    
    <update id="updateUser" >
       update t_user set username=#{username},password=#{password},age=#{age} where id=#{id}
    </update>
    
    <select id="selectUserById" parameterType="int" resultType="com.mybatis.pojo.User">
       select * from t_user where id=#{id}
    </select>
    
</mapper>

七、快速添加 MyBatis 配置文件

创建 xml 文件 mybatis-comfig.xml，具体配置如下：

<?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 MyBatis 运行环境 -->
    <environments default="development">
        <environment id="development">
            <!-- 配置 JDBC 事务管理 -->
            <transactionManager type="JDBC" />
            <!-- POOLED 配置 JDBC 数据源连接池 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis_db?useUnicode=true&amp;characterEncoding=UTF-8" />
                <property name="username" value="root" />
                <property name="password" value="" />
            </dataSource>
        </environment>
    </environments>
    
    <!-- 注册 UserDAO.xml -->
    <mappers>
        <mapper resource="com/mybatis/dao/UserDaoMapper.xml"/>
    </mappers>
    
</configuration>

八、快速创建测试类

创建测试类 Test.java，代码如下：

package com.mybatis.test;

import java.io.InputStream;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.mybatis.dao.UserDao;
import com.mybatis.pojo.User;

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

        //加载MyBatis配置文件
        InputStream is = Test.class.getClassLoader().getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);

        //获取SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //获取实现接口的代理对象
        UserDao userDAO = sqlSession.getMapper(UserDao.class);
        
        //新增用户
        User user = new User();
        user.setUsername("孔乙己");
        user.setPassword("123456");
        user.setAge(21);
        System.out.println(userDAO.addUser(user));
        sqlSession.commit();
        
//      //删除用户
//      System.out.println(userDAO.deleteUser(1));
//      sqlSession.commit();
//
//      //查询用户
//      User user1 = userDAO.selectUserById(1);
//      System.out.println(user1);
//
//      //修改用户
//      User user2 = userDAO.selectUserById(1);
//      user2.setUsername("指南者");
//      System.out.println(userDAO.updateUser(user2));
//      sqlSession.commit();

    }
}

九、测试运行，结果如下图：

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