spring boot + mybatis实现一对一，一对多的样码之一种-白红宇

实现的方法，有两种不同的风格，

一种是直接在接口里用注解实现，

另一种还是稳重的写xml，用resultmap来搞定。

经过几天的复习，

这个知识点差不多了。

参考URL：

http://blog.csdn.net/KingBoyWorld/article/details/78966789

建表语句：

CREATE TABLE IF NOT EXISTS `user` (  `id` int(11) NOT NULL AUTO_INCREMENT,  `nick_name` varchar(50) DEFAULT NULL,  `address_id` int(11) DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8;CREATE TABLE IF NOT EXISTS `address` (  `id` int(11) NOT NULL AUTO_INCREMENT,  `province` varchar(50) DEFAULT NULL,  `city` varchar(50) DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8;CREATE TABLE IF NOT EXISTS `car` (  `id` int(11) NOT NULL AUTO_INCREMENT,  `color` varchar(50) DEFAULT NULL,  `name` varchar(50) DEFAULT NULL,  `user_id` int(11) DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8;INSERT INTO    `user`VALUES    ('1', 'baby', '1'),    ('2', 'kingboy', '2'),    ('3', 'boy', '3'),    ('4', 'kingbaby', '4');INSERT INTO    `address`VALUES    ('1', '北京', '北京'),    ('2', '天津', '天津'),    ('3', '安徽', '宿州'),    ('4', '广东', '广州');INSERT INTO    `car`VALUES    ('1', 'green', '路虎', '1'),    ('2', 'white', '奔驰', '2'),    ('3', 'blue', '玛莎拉蒂', '4'),    ('4', 'yellow', '兰博基尼', '4');

几个pojo，注意的是没有用外键关联，只是用了外键来对应，哪个表需要取外面的关联的，就要在POJO里建立对应的属性。

package opsstock.paic.com.cn.entity;public class Address {	private Long id;	private String province;	private String city;	public Long getId() {		return id;	}	public void setId(Long id) {		this.id = id;	}	public String getProvince() {		return province;	}	public void setProvince(String province) {		this.province = province;	}	public String getCity() {		return city;	}	public void setCity(String city) {		this.city = city;	}	@Override	public String toString() {		return "Address [id=" + id + ", province=" + province + ", city=" + city + "]";	}		}

package opsstock.paic.com.cn.entity;import java.util.List;public class User {	private Long id;	private String name;	private Address address;	private Long addressId;	private List
    
      cars;	public Long getId() {		return id;	}	public void setId(Long id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public Address getAddress() {		return address;	}	public void setAddress(Address address) {		this.address = address;	}	public Long getAddressId() {		return addressId;	}	public void setAddressId(Long addressId) {		this.addressId = addressId;	}	public List
     
       getCars() {		return cars;	}	public void setCars(List
      
        cars) {		this.cars = cars;	}	@Override	public String toString() {		return "User [id=" + id + ", name=" + name + ", addressId=" + addressId + "]";	}		}

package opsstock.paic.com.cn.entity;public class Car {	private Long id;	private String name;	private String color;	private Long userId;	public Long getId() {		return id;	}	public void setId(Long id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public String getColor() {		return color;	}	public void setColor(String color) {		this.color = color;	}	public Long getUserId() {		return userId;	}	public void setUserId(Long userId) {		this.userId = userId;	}	@Override	public String toString() {		return "Car [id=" + id + ", name=" + name + ", color=" + color + ", userId=" + userId + "]";	}		}

相关mapper的写法，我总觉得，应该可以简化那个路径吧。

package opsstock.paic.com.cn.mapper;import org.apache.ibatis.annotations.Select;import opsstock.paic.com.cn.entity.Address;public interface AddressRepository {		@Select("SELECT * FROM `address` WHERE id = #{id}")	Address findAddressById(Long id);}

package opsstock.paic.com.cn.mapper;import java.util.List;import org.apache.ibatis.annotations.Select;import opsstock.paic.com.cn.entity.Car;public interface CarRepository {		@Select("SELECT * FROM `car` WHERE user_id = #{userId}")	List
    
      findCarByUserId(Long userId);}

注意@One和@Many的注解哟

package opsstock.paic.com.cn.mapper;import org.apache.ibatis.annotations.Result;import org.apache.ibatis.annotations.Results;import org.apache.ibatis.annotations.Select;import org.apache.ibatis.annotations.One;import org.apache.ibatis.annotations.Many;import opsstock.paic.com.cn.entity.User;public interface UserRepository {		@Select("SELECT * FROM `user` WHERE id=#{id}")	@Results({		@Result(property="address", column="address_id", 				one = @One(select = "opsstock.paic.com.cn.mapper.AddressRepository.findAddressById"))	})	User findUserWithAddress(Long id);			@Select("SELECT * FROM `user` WHERE id = #{id}")	@Results({		@Result(property="cars", column="id",				many = @Many(select="opsstock.paic.com.cn.mapper.CarRepository.findCarByUserId"))	})	User getUserWithCar(Long id);}

省掉service，直接测试：

package opsstock.paic.com.cn.controller;import javax.annotation.Resource;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;import opsstock.paic.com.cn.entity.User;import opsstock.paic.com.cn.mapper.UserRepository;@RestController@RequestMapping(value="/user")public class UserController {		@Resource	UserRepository userRepository;		@GetMapping(value="/id/{id}/include/address")	public String findUserWithAddress(@PathVariable Long id) {		User userWithAddress = userRepository.findUserWithAddress(id);		return userWithAddress.getAddress().toString();	}			@GetMapping(value = "/id/{id}/include/car")    public String findUserWithCar(@PathVariable Long id) {        User user = userRepository.getUserWithCar(id);        return user.getCars().toString();    }	}

则输入网址：

http://localhost:8080/user/id/4/include/car

返回结果：

(没有理会乱码之事)