01-Mybaties

1. 搭建环境
2. 依赖maven创建项目，并将此项目作为父项目导入依赖的jar包
3. 依据父项目，创建模板，在resources下创建mybatis-config.xml文件，并导入核心配置文件

   <?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">
   <!--核心配置文件   sqlconfig-->
   <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/jdbc?useSSL=true&amp;useUniode=true&amp;characterEncoding=UTF-8"/>
                   <property name="username" value="root"/>
                   <property name="password" value="root"/>
               </dataSource>
           </environment>
       </environments>
       <mappers>
           <mapper resource="

   <mappers>
       <mapper resource="./UserMapper.xml"/>
   </mappers>

   "/> </mappers> </configuration>

4. 创建一个工具类用于获取SqlSession对象

   package com.neusoft.utils;
   
   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;
   
   //工具类    创建SqlSession工厂    生产SqlSession
   public class MybatisUtils {
       private static SqlSessionFactory sqlSessionFactory;
       static{
           try {
   //            使用mybatis获取SqlSessionFactory对象
               String resource="mybatis-config.xml";
               InputStream inputStream = null;
               inputStream = Resources.getResourceAsStream(resource);
               sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   
   //    获取一个sqlsession对象，用于操作数据库
       public static SqlSession getsqlsession(){
           return sqlSessionFactory.openSession();
   
       }
   
   }

5. 创建操作数据的接口dao

   public interface UserDao {
       List<User> getUserList();
   }

6. 编写对应的mapper.xml文件

   <?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">
   <!--        namespace绑定一个对应的dao/mapper接口-->
   <mapper namespace="com.neusoft.dao.UserDao">
       <select id="getUserList" resultType="com.neusoft.entity.User">
       select * from users
     </select>
   </mapper>

7. 编写测试类

   package com.neusoft.dao;
   
   import com.neusoft.entity.User;
   import com.neusoft.utils.MybatisUtils;
   import org.apache.ibatis.session.SqlSession;
   import org.junit.Test;
   
   import java.util.List;
   
   public class UserDaoTest {
   
       @Test
       public void test(){
           SqlSession sqlsession= MybatisUtils.getsqlsession();
           UserDao mapper= sqlsession.getMapper(UserDao.class);
           List<User> list= mapper.getUserList();
           for (User u:list){
               System.out.println(u);
           }
   
       }
   }

8. 注意点

• namespace的重要性：必须配置namespace，否则xml文件中标签中的操作语句将没有入口，就无法自动映射进对应接口的抽象方法