MyBatis第一个程序

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已于 2023-02-24 14:41:51 修改

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文章标签： mybatis java mysql

于 2023-02-23 16:47:38 首次发布

本文链接：https://blog.youkuaiyun.com/Science888666/article/details/129184973

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文章详细介绍了如何搭建Mybatis环境，包括创建数据库、导入Mybatis和MySQL相关jar包，编写MyBatis配置文件、Mapper接口和XML配置，以及测试类进行数据查询。还提到了可能遇到的Maven静态资源过滤问题。

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思路流程：搭建环境—>导入Mybatis—->编写代码—->测试

2.1、代码演示

搭建实验数据库

CREATE DATABASE `mybatis`;
USE `mybatis`;
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int(20) NOT NULL,
  `name` varchar(30) DEFAULT NULL,
  `pwd` varchar(30) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
insert  into `user`(`id`,`name`,`pwd`) values (1,'小王','123456'),(2,'张三','abcdef'),(3,'李四','987654');

导入MyBatis相关 jar 包

GitHub上找

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.2</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.47</version>
</dependency>

编写MyBatis核心配置文件

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="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=utf8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/wzw/dao/userMapper.xml"/>
    </mappers>
</configuration>

编写MyBatis工具类

查看帮助文档

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 resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    //获取SqlSession连接
    public static SqlSession getSession(){
        return sqlSessionFactory.openSession();
    }
}

创建实体类

public class User {
    private int id;  //id
    private String name;   //姓名
    private String pwd;   //密码
    //构造,有参,无参
    //set/get
    //toString()
}

编写Mapper接口类

import com.wzw.pojo.User;
import java.util.List;
public interface UserMapper {
    List<User> selectUser();
}

编写Mapper.xml配置文件

namespace 十分重要，不能写错！

<?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.kuang.dao.UserMapper">
  <select id="selectUser" resultType="com.kuang.pojo.User">
    select * from user
  </select>
</mapper>

编写测试类

Junit 包测试

public class MyTest {
    @Test
    public void selectUser() {
        SqlSession session = MybatisUtils.getSession();
        //方法一:
        //List<User> users = session.selectList("com.kuang.mapper.UserMapper.selectUser");
        //方法二:
        UserMapper mapper = session.getMapper(UserMapper.class);
        List<User> users = mapper.selectUser();
        for (User user: users){
            System.out.println(user);
        }
        session.close();
    }
}

运行测试

2.2、问题说明

可能出现问题说明：Maven静态资源过滤问题

<resources>
    <resource>
        <directory>src/main/java</directory>
        <includes>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
        </includes>
        <filtering>false</filtering>
    </resource>
    <resource>
        <directory>src/main/resources</directory>
        <includes>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
        </includes>
        <filtering>false</filtering>
    </resource>
</resources>