快速上手Mybatis项目

快速上手Mybatis项目

思路流程：搭建环境-->导入Mybatis--->编写代码--->测试

1、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,'白白','123456'),(2,'张三','abcdef'),(3,'李四','987654');

2、导入MyBatis相关 jar 包

<dependencies>
    <!--spring框架-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.1.10.RELEASE</version>
        </dependency>
    <!--mybatis框架-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
    <!-- mysql启动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.30</version>
        </dependency>
    </dependencies>

3、编写MyBatis核心配置文件

<?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">
<configuration>

    <typeAliases>
        <package name="com.bai.pojo"/>
    </typeAliases>

    <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/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <package name="com.bai.dao"/>
    </mappers>
</configuration>

4、编写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 {
       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();
  }

}

5、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()
   
}

6、编写Mapper接口类

import com.bai.pojo.User;
import java.util.List;

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

7、编写Mapper.xml配置文件

• namespace 十分重要，不能写错！是接口全类名

<?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>

8、编写测试类

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();
  }
}

9、运行测试，成功的查询出来的我们的数据，ok！

如果报错：

BindingException: Invalid bound statement (not found):

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>