Mybatis的简单使用-优快云博客

本文介绍了如何搭建Mybatis环境，包括Java、Mysql、Maven和IDEA的安装，然后创建Maven项目并引入Mybatis和Mysql驱动依赖。接着配置mybatis-config.xml文件，建立数据库连接，编写User实体类、UserMapper接口及对应的XML配置文件，最后通过JUnit测试执行查询操作，成功打印出用户列表。

我的第一个Mybatis程序

1.环境需求

jdk8+ https://www.oracle.com/cn/java/technologies/javase/javase-jdk8-downloads.html
Mysql5.7.32 https://dev.mysql.com/downloads/mysql/
maven3.6.1 http://maven.apache.org/download.cgi
IDEA https://www.jetbrains.com/idea/

2.搭建数据库

作为测试用的的数据

create database `mybatis`;
use `mybatis`;

CREATE TABLE `user`(
  `id` INT(10) NOT NULL PRIMARY KEY,
  `name` VARCHAR(20) DEFAULT NULL,
  `pwd` VARCHAR(20) DEFAULT NULL
)

INSERT  INTO `user`(`id`,`name`,`pwd`) VALUES 
(1,'刘备','123456'),(2,'关羽','666666'),(3,'张飞','987654');

3.使用IDEA创建Maven项目

在这里插入图片描述

4.导入mybatis依赖

<!--mysql-->
        <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>

5.mybatis核心配置文件

在src/main/resources目录下创建mybatis-config.xml
可以在官网查看帮助文档

<?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>
   <environments default="test">
       <environment id="test">
           <transactionManager type="JDBC"/>
           <dataSource type="POOLED">
               <property name="driver" value="com.mysql.jdbc.Driver"/>
               <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&amp;useUnicode=true&amp;characterEncoding=utf8"/>
               <property name="username" value="root"/> <!--你的账号-->
               <property name="password" value="root"/> <!--你的密码-->
           </dataSource>
       </environment>
   </environments>
   <mappers>
       <mapper resource="dao/userMapper.xml"/> <!--路径为下面的userMapper.xml文件路径-->
   </mappers>
</configuration>

6.mybatis工具类

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 {
           String resource = "mybatis-config.xml";
           InputStream inputStream = Resources.getResourceAsStream(resource);
           sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
   } 
   public static SqlSession getSession(){
       return sqlSessionFactory.openSession();
   }
}

7.实体类

public class User {
  private int id;  
  private String name;   
  private String password;
  //以下省略部分代码
  //构造方法,有参,无参
  //set(),get()
  //toString()方法   
}

8.Mapper接口类

import java.util.List;

public interface UserMapper {
   List<User> selectUsers();
}

9.Mapper.xml配置文件

namespace为以上UserMapper接口类路径
id为上面的方法名
resultType为实体类路径
select * from user 查询语句

<?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="dao.UserMapper">       
 <select id="selectUsers" resultType="bean.User">
		  select * from user
 </select>
</mapper>

10.junit测试

 @Test
   public void selectAllUsers() {
       SqlSession session = MybatisUtils.getSession();
      
       UserMapper mapper = session.getMapper(UserMapper.class);
       
       List<User> users = mapper.selectUsers();

       for (User user: users){
           System.out.println(user);
      	}
       session.close();
  	}
}