初窥MyBatis-普通的CRUD操作

编写接口 编写对应的Mapper.

• 编写接口
• 编写对应的Mapper.
• 测试（增删改需要提交事务）

<mapper namespace="com.perwrj.dao.UserMapper"><!-- 查询 id="重写的方法名" resultType="返回值类型（全类名）" --> <select id="getUserList" resultType="com.perwrj.pojo.User"> select * from mybatis.user </select></mapper>

• id：就是对应的namespace中的方法名
• resultType：sql语句的返回值类型
• parameterType：传入参数的类型

package com.perwrj.dao;import java.util.List;import com.perwrj.pojo.User;public interface UserMapper {//	查询全部用户	List<User> getUserList();//	根据id查询用户	User getUserById(int id);//	添加一个用户	int addUser(User user);//	修改用户	int updateUser(User user);//	删除用户	int deleteUser(int id);}

<?

package com.perwrj.dao;import java.util.List;import org.apache.ibatis.session.SqlSession;import org.junit.Test;import com.perwrj.pojo.User;import com.perwrj.utils.MyBatisUtil;public class UserMapperTest {	@Test	public void test() {		//获得SqlSession对象，		SqlSession sqlSession = MyBatisUtil.getSqlSession();				try {//			方式一：getMapper执行sql:更加简洁，类型更加安全，推荐使用						 UserMapper userMapper = sqlSession.getMapper(UserMapper.class); List<User>			 userList = userMapper.getUserList();						 for (User user : userList) { System.out.println(user); }				//方式一结束			//			方式二：老方法，不建议使用，			/*			 * List<User> list =			 * sqlSession.selectList("com.perwrj.dao.UserMapper.getUserList");			 * 			 * for (User object : list) { System.out.println(object); }			 */			//方式二结束		}catch(Throwable e) {			e.printStackTrace();		}finally {//			关闭sqlSession			sqlSession.close();		}		}	/**	 * 删除操作	 */	@Test	public void deleteUserTest() {		SqlSession sqlSession = MyBatisUtil.getSqlSession();				try {			UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 			int num = userMapper.deleteUser(4);			if(num > 0) {//				提交事务				System.out.println(num);//1				sqlSession.commit();				sqlSession.close();			}		}catch(Throwable e) {			e.printStackTrace();		}finally {			sqlSession.close();		}			}													/**	 * 改操作	 */	@Test	public void updateUserTest() {		SqlSession sqlSession = MyBatisUtil.getSqlSession();				try {			UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 			int num = userMapper.updateUser(new User(2,"杰瑞","987654"));			if(num > 0) {//				提交事务				System.out.println(num);//1				sqlSession.commit();				sqlSession.close();			}		}catch(Throwable e) {			e.printStackTrace();		}finally {			sqlSession.close();		}				}		/**	 * 增删改需要提交事务	 */	@Test	public void addUserTest() {		SqlSession sqlSession = MyBatisUtil.getSqlSession();						try {			UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 			int num = userMapper.addUser(new User(4,"王瑞杰","123568"));			if(num > 0) {//				提交事务				System.out.println(num);//1				sqlSession.commit();				sqlSession.close();			}		}catch(Throwable e) {			e.printStackTrace();		}finally {			sqlSession.close();		}		}		@Test	public void testGetUserById() {		//获得SqlSession对象，		SqlSession sqlSession = MyBatisUtil.getSqlSession();				try {			 UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 			 User user = userMapper.getUserById(1);			 System.out.println(user);		}catch(Throwable e) {			e.printStackTrace();		}finally {			sqlSession.close();		}		}	}

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编写接口编写对应的Mapper.编写接口编写对应的Mapper.测试（增删改需要提交事务）<mappernamespace="com.perwrj.dao.UserMapper"><!--查询id="重写的方法名"resultType="返回值类型（全类名）"--><selectid="getUserList"resultTyp
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