[FIXED] Error accessing field : using @OneToMany Annotation in Hibernate

Issue

I want to have the relationship OneToMany between two entity but I have this error when I try to save object into database:

on console

java.lang.IllegalArgumentException: Can not set java.lang.Long field com.pi.MinuteBrico.models.Category.idCtegory to java.util.LinkedHashMap
    at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167) ~[na:na]
    at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171) ~[na:na]
    at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58) ~[na:na]
    at java.base/jdk.internal.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:36) ~[na:na]
    at java.base/java.lang.reflect.Field.get(Field.java:419) ~[na:na]

on psotman

org.springframework.orm.jpa.JpaSystemException: Error accessing field [private java.lang.Long com.pi.MinuteBrico.models.Category.idCtegory] by reflection for persistent property [com.pi.MinuteBrico.models.Category#idCtegory] : {name=Mecanique}; nested exception is org.hibernate.property.access.spi.PropertyAccessException: Error accessing field [private java.lang.Long com.pi.MinuteBrico.models.Category.idCtegory] by reflection for persistent property [com.pi.MinuteBrico.models.Category#idCtegory] : {name=Mecanique}\r\n\tat org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:331)\r\n\tat org.springframework.orm.jpa.vendor.

my entities classes:

1: Bricoleur.java

    package com.pi.MinuteBrico.models;

import java.util.Map;
import java.io.Serializable;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;




@Entity
@Table(name = "Bricoleur")
public class Bricoleur implements Serializable  {

    /**
     *@author iliass Alilou
     */
    private static final long serialVersionUID = 1L;
    /*@SequenceGenerator(
            name = "Bricoleur_sequence",
            sequenceName = "Bricoleur_sequence",
            allocationSize = 1
    )
    @Id
    @GeneratedValue(
            strategy = GenerationType.SEQUENCE,
            generator = "Bricoleur_sequence"
    )*/
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id; 
    private String photo;
    private String firstName;
    private String lastName;
    private String email;
    private String phone;
    private String birthDate;
    private String adresse;
    
    @OneToMany(/*fetch = FetchType.LAZY , targetEntity = Category.class,*/ cascade = CascadeType.ALL)
    @JoinColumn(name = "BricoCategory_Bricoleur",referencedColumnName = "id")
    private List<Category> category ;
    

    public Bricoleur() {
        
    }
    public Bricoleur(String photo,
                     String firstName, 
                     String lastName, 
                     String email, 
                     String phone, 
                     String birthDate,
                     String adresse
                     ) {
        super();
        this.photo = photo;
        this.firstName = firstName;
        this.lastName = lastName;
        this.email = email;
        this.phone = phone;
        this.birthDate = birthDate;
        this.adresse = adresse;
    }
   // setters and getters
   ... ..
    
}

2:Category

    package com.pi.MinuteBrico.models;
import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="Category")
public class Category implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long idCtegory;    
    private String name;
    
    public Category() {
        
    }
    
    

    public Category(String name) {
        super();
        this.name = name;
    }

    // Stters and getters

    
}

JSON file to save

    {
    "photo":"test",
    "firstName":"iliass",
    "lastName":"alilou",
    "email":"[email protected]",
    "phone":"0654248574",
    "birthDate":"18/08/1999",
    "adresse":"xxxxxxxxxxxx",
     "category" : [
         {
             "name" : "Mecanique"
         },
         {
             "name" : "Plombie"
         }
     ] 
}

In my Controller

@CrossOrigin()
@PostMapping("/bricoleur")
public String create(@RequestBody Map<String, Object> bricoleurMap) {
    System.out.println(bricoleurMap);
    Bricoleur bricoleur = new Bricoleur(bricoleurMap);
    bricoleurService.saveBricoleur(bricoleur);
    return "Bricoleur ajouté";

}

Service

public Bricoleur saveBricoleur(Bricoleur bricoleur) {
    return bricoleurRepository.save(bricoleur);
}

Solution

The field category is of type List:

List<Category> category 

but it seems you are trying to assign a LinkedHashMap, that's a Map.

Didn't you mean to use a LinkedList? We need to see how you are assigning the field category to help you more.

Answered By - Davide