Mybatis02、MyBatis第一个程序

思路流程：搭建环境—>导入Mybatis—->编写代码—->测试

2.1、代码演示

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,'狂神','123456'),(2,'张三','abcdef'),(3,'李四','987654');

   导入MyBatis相关 jar 包

• GitHub上找

  ependency>
    <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/kuang/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

  blic 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.kuang.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();
    }
  }
  

  2.2、问题说明

  可能出现问题说明：Maven静态资源过滤问题

  sources>
    <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>