六、Mybatis注解开发-编程知识

1.MyBatis的常用注解

注解开发越来越流行， Mybatis也可以使用注解开发方式，这样就可以减少编写Mapper映射文件。
@Insert：实现新增
@Update：实现更新
@Delete：实现删除
@Select：实现查询
@Result：实现结果集封装
@Results：可以与@Result 一起使用，封装多个结果集
@One：实现一对一结果集封装
@Many：实现一对多结果集封装

2.MyBatis的注解增删改查

mapper：

package com.cookie.mapper;import com.cookie.pojo.User;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;import java.util.List;public interface UserMapper {List<User> findAll();List<User> findAllUserAndRole();//添加用户@Insert("insert into user values(#{id},#{username},#{password},#{birthday})")void addUser(User user);//更新用户@Update("update user set username = #{username} where id=#{id}")void updateUser(User user);//查询用户@Select("select * from user")List<User> selectUser();//删除用户@Delete("delete from user where id = #{id}")void deleteUser(Integer id);}

    <mappers><!--扫描使用注解的类--><mapper class="com.cookie.mapper.UserMapper"></mapper></mappers>

测试：

package com.cookie.test;import com.cookie.mapper.OrderMapper;
import com.cookie.mapper.UserMapper;
import com.cookie.pojo.Order;
import com.cookie.pojo.User;
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 org.junit.Before;
import org.junit.Test;import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;public class MybatisTest {private UserMapper userMapper;@Beforepublic void before() throws IOException {InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = sqlSessionFactory.openSession(true);userMapper = sqlSession.getMapper(UserMapper.class);}@Testpublic void addUser(){User user = new User();user.setId(3);user.setUsername("12");user.setPassword("34");user.setBirthday(new Date());userMapper.addUser(user);}@Testpublic void selectUser(){List<User> users = userMapper.selectUser();for (User user : users) {System.out.println(user);}}@Testpublic void deleteUser(){userMapper.deleteUser(3);}@Testpublic void updateUser(){User user = new User();user.setId(1);user.setUsername("hahaha");userMapper.updateUser(user);}
}

3.MyBatis的注解实现复杂映射开发

实现复杂关系映射之前可以在映射文件中通过配置来实现，使用注解开发后，可以使用@Results注解，@Result注解， @One注解， @Many注解组合完成复杂关系的配置

4.一对一查询

package com.cookie.mapper;import com.cookie.pojo.Order;
import com.cookie.pojo.User;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;import java.util.List;public interface OrderMapper {@Select("select * from orders")@Results({@Result(id = true,property = "id",column = "id"),@Result(property = "orderTime",column = "orderTime"),@Result(property = "total",column = "total"),@Result(property = "user",column = "uid",javaType = User.class,one = @One(select = "com.cookie.mapper.UserMapper.findUserById"))})List<Order> findAllOrders();}

package com.cookie.mapper;import com.cookie.pojo.Order;
import com.cookie.pojo.User;
import org.apache.ibatis.annotations.*;import java.util.List;public interface UserMapper {//根据id查询用户信息@Select("select * from user where id = #{id}")User findUserById(Integer id);}

    @Testpublic void findAllOrders(){List<Order> allOrders = orderMapper.findAllOrders();for (Order allOrder : allOrders) {System.out.println(allOrder);}}

5.一对多查询

sql：

select * from user;
select * from orders where uid=查询出用户的id;

mapper：

public interface UserMapper {@Select("select * from user")@Results({@Result(id = true,property = "id",column = "id"),@Result(property = "username",column = "username"),@Result(property = "password",column = "password"),@Result(property = "birthday",column = "birthday"),@Result(property = "orderList",column = "id",javaType = List.class,many = @Many(select = "com.cookie.mapper.OrderMapper.findOrderByUid"))})List<User> findAllUserAndOrder();
}

public interface OrderMapper {@Select("select * from orders where uid = #{uid}")List<Order> findOrderByUid(Integer uid);}

    @Testpublic void findAllUserAndOrder(){List<User> allUserAndOrder = userMapper.findAllUserAndOrder();for (User user : allUserAndOrder) {System.out.println(user);}}

6.多对多查询

sql:

select * from user;
select * from role r,user_role ur where r.id=ur.role_id and ur.user_id=用户的id

mapper：

public interface UserMapper {@Select("select * from user")@Results({@Result(id = true,property = "id",column = "id"),@Result(property = "username",column = "username"),@Result(property = "password",column = "password"),@Result(property = "birthday",column = "birthday"),@Result(property = "roleList",column = "id",javaType = List.class,many = @Many(select = "com.cookie.mapper.RoleMapper.findById"))})List<User> findAllUserAndRoles();}

package com.cookie.mapper;import com.cookie.pojo.Role;
import org.apache.ibatis.annotations.Select;import java.util.List;public interface RoleMapper {@Select("select * from sys_role r,sys_user_role ur where r.id = ur.roleid and ur.userid=#{uid}")List<Role> findById(Integer uid);}

    @Testpublic void findAllUserAndRoles(){List<User> allUserAndRoles = userMapper.findAllUserAndRoles();for (User allUserAndRole : allUserAndRoles) {System.out.println(allUserAndRole);}}