无法让spring boot hibernate rest api返回一对多关系

Posted 2023-02-19

【中文标题】无法让spring boot hibernate rest api返回一对多关系

【英文标题】：Cant get spring boot hibernate rest api to return a one to many relationship

【发布时间】：2022-01-20 18:08:48

【问题描述】：

我用建筑模型和地板模型为停车场建模。建筑物和楼层之间存在一对多的关系。我已经建立了一个休息控制器来检索数据。我正在尝试通过对api/v1/parkingbuildings/1/ 的简单获取请求来检索数据。问题是，在检索建筑物时，根据我的关系映射，我没有看到楼层列表。对我可能犯的任何错误的任何见解将不胜感激。下面是返回的json；

"building_id":1,"building_name":"Labadiestad","postcode":"SA78BQ","max_floors":14,"owner_name":"Schaefer, Gutmann and Braun"

我希望在有效载荷中看到一系列楼层，但我无法理解为什么，我编写了其他类似的更简单的解决方案，它们可以毫无问题地做同样的事情，我比较了我以前的解决方案，发现我的方法没有什么不同。

这是我的建筑模型

package com.admiral.reslink.models;

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

import javax.persistence.*;
import java.util.ArrayList;
import java.util.List;

@Entity(name = "parking_buildings")
@JsonIgnoreProperties("hibernateLazyInitializer", "handler")
public class ParkingBuilding 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long building_id;

    private String building_name;
    private String postcode;
    private int max_floors;
    private String owner_name;

    // ToDo sort the relationships

    @OneToMany(mappedBy = "parkingBuilding")
    @JsonIgnore
    private List<ParkingFloor> parkingFloors;

    public ParkingBuilding() 
    

    public long getBuilding_id() 
        return building_id;
    

    public void setBuilding_id(long building_id) 
        this.building_id = building_id;
    

    public String getBuilding_name() 
        return building_name;
    

    public void setBuilding_name(String building_name) 
        this.building_name = building_name;
    

    public String getPostcode() 
        return postcode;
    

    public void setPostcode(String postcode) 
        this.postcode = postcode;
    

    public int getMax_floors() 
        return max_floors;
    

    public void setMax_floors(int max_floors) 
        this.max_floors = max_floors;
    

    public String getOwner_name() 
        return owner_name;
    

    public void setOwner_name(String owner_name) 
        this.owner_name = owner_name;
    

    public List<ParkingFloor> getParkingFloors() 
        return parkingFloors;
    

    public void setParkingFloors(List<ParkingFloor> parkingFloors) 
        this.parkingFloors = parkingFloors;
    

这是我的地板模型

package com.admiral.reslink.models;

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

import javax.persistence.*;
import java.util.List;

@Entity
@Table(name = "parking_floors")
@JsonIgnoreProperties("hibernateLazyInitializer", "handler")

public class ParkingFloor 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long floor_id;

    private int floor_number;
    private int max_height_inches;
    private boolean is_covered;
    private boolean is_disabled_access;

    // ToDo sort the relationships
    @ManyToOne
    @JoinColumn(name="building_id", nullable=false)
    private ParkingBuilding parkingBuilding;

    @OneToMany(mappedBy = "parkingFloor")
    @JsonIgnore
    private List<ParkingSpace> parkingSpace;

    public ParkingFloor() 
    

    public long getFloor_id() 
        return floor_id;
    

    public void setFloor_id(long floor_id) 
        this.floor_id = floor_id;
    

    public int getFloor_number() 
        return floor_number;
    

    public void setFloor_number(int floor_number) 
        this.floor_number = floor_number;
    

    public int getMax_height_inches() 
        return max_height_inches;
    

    public void setMax_height_inches(int max_height_inches) 
        this.max_height_inches = max_height_inches;
    

    public boolean isIs_covered() 
        return is_covered;
    

    public void setIs_covered(boolean is_covered) 
        this.is_covered = is_covered;
    

    public boolean isIs_disabled_access() 
        return is_disabled_access;
    

    public void setIs_disabled_access(boolean is_disabled_access) 
        this.is_disabled_access = is_disabled_access;
    

    public ParkingBuilding getParkingBuilding() 
        return parkingBuilding;
    

    public void setParkingBuilding(ParkingBuilding parkingBuilding) 
        this.parkingBuilding = parkingBuilding;
    

    public List<ParkingSpace> getParkingSpace() 
        return parkingSpace;
    

    public void setParkingSpace(List<ParkingSpace> parkingSpace) 
        this.parkingSpace = parkingSpace;
    

这是我的建筑控制器

package com.admiral.reslink.controllers;

import com.admiral.reslink.models.ParkingBuilding;
import com.admiral.reslink.models.ParkingFloor;
import com.admiral.reslink.repositories.ParkingBuildingRepository;
import com.admiral.reslink.repositories.ParkingFloorRepository;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api/v1/parkingbuildings")
public class ParkingBuildingController 

    @Autowired
    private ParkingBuildingRepository parkingBuildingRepository;

    @GetMapping
    public List<ParkingBuilding> list() return parkingBuildingRepository.findAll();

    @GetMapping
    @RequestMapping("id")
    public ParkingBuilding get(@PathVariable Long id) return  parkingBuildingRepository.getById(id);

    @PostMapping
    public ParkingBuilding create(@RequestBody final ParkingBuilding parkingBuilding) 
        return parkingBuildingRepository.saveAndFlush(parkingBuilding);
    

    @RequestMapping(value="id", method = RequestMethod.DELETE)
    public void delete(@PathVariable Long id) 
        parkingBuildingRepository.deleteById(id);
    

    @RequestMapping(value="id", method = RequestMethod.PUT)
    public ParkingBuilding update(@PathVariable Long id, @RequestBody ParkingBuilding parkingBuilding) 
        ParkingBuilding existingParkingBuilding = parkingBuildingRepository.getById(id);
        BeanUtils.copyProperties(parkingBuilding, existingParkingBuilding, "building_id");
        return parkingBuildingRepository.saveAndFlush(existingParkingBuilding);
    

【问题讨论】：

可能是一个错误，但您在问题中写的 building 和 floor 模型是相同的。

#1 我们还需要看看你是如何查询 ParkingBuilding 的：hibernate、spring 存储库等 #2 你能打印出parkingFloors 的值，然后将其作为响应发送吗？

【参考方案1】：

不确定您是如何检索地板的。 OneToMany 默认为lazy，除非被询问，否则不会加载。

在您的存储库中，尝试：

@EntityGraph(attributePaths = "parkingFloors")
ParkingBuilding findById(long id);