Passing JSON in body spring and constructing object with foreign key - spring

Question

I am trying to create a basic spring API.
I have a Post class that have an attribute User user as foreign key.
package com.example.demo.model;
import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
import jakarta.persistence.*;
import java.util.Objects;
#Entity
public class Post {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(nullable = false, updatable = false)
private Long id;
private String title;
private String body;
#ManyToOne
private User user;
public Post() {
}
public Post(String title, String body) {
this.title = title;
this.body = body;
}
// Getters and Settes ...
}
Here is the User class
package com.example.demo.model;
import jakarta.persistence.*;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
#Entity
public class User implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(nullable = false, updatable = false)
private Long id;
private String name;
private Integer age;
private String email;
#OneToMany(mappedBy = "user")
private List<Post> posts = new ArrayList<Post>();
#ManyToMany
#JoinTable(name = "user_task",
joinColumns = #JoinColumn(name = "user_id"),
inverseJoinColumns = #JoinColumn(name = "task_id"))
private List<Task> tasks = new ArrayList<Task>();
public User() {}
public User(String name, Integer age, String email) {
this.name = name;
this.age = age;
this.email = email;
}
// Getters and Settes ...
}
and here is my Post Controller
package com.example.demo.controller;
import com.example.demo.model.Post;
import com.example.demo.service.PostService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;
#RestController
#RequestMapping("/post")
public class PostController {
private final PostService postService;
#Autowired
public PostController(PostService postService) {
this.postService = postService;
}
#GetMapping("/all")
public List<Post> getAllPosts (){
System.out.println("3");
return postService.getAllPosts();
}
#GetMapping("/{id}")
public Post getPost(#PathVariable Long id){
System.out.println("2");
return postService.getPost(id);
}
#PostMapping("/create")
public Post createPost(#RequestBody Post post){
return postService.createPost(post);
}
}
So in the /create endpoint i am passing a json object in the body. Here is an exemple:
{
"title": "Post1",
"body": "Post1 Body",
"user": "1"
}
the user: 1 is the foreign key to user who owns the post.
Here is the full error:
Resolved [org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot construct instance of `com.example.demo.model.User` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('1')]
I need to insert the json object into the Post table with the foreign key