ManyToMany relationship not working when executing query (Spring Data JPA)

Question

I have a UserEntity and a RoleEntity. The UserEntity contains a field "roles" which is of type HashSet and annotated with the @ManyToMany annotation. When calling my custom query "findByEmail" it successfully fetches the UserEntity, but the roles set keeps empty.

Here some parts of the code:

UserEntity.java

package xyz.michaeltprojects.collchecklist.security.persistence;

import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

import javax.persistence.*;
import javax.validation.constraints.Email;
import javax.validation.constraints.NotBlank;
import javax.validation.constraints.Size;
import java.util.HashSet;
import java.util.Set;
import java.util.UUID;

@Entity
@Table(name = "users")
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
public class UserEntity {

    @Id
    @GeneratedValue
    private UUID id;

    @NotBlank
    @Size(min = 3, max = 30)
    private String username;

    @NotBlank
    @Size(min = 6, max = 50)
    @Email
    private String email;

    @NotBlank
    @Size(max = 120)
    private String password;

    @ManyToMany(fetch = FetchType.EAGER)
    @JoinTable(name = "user_roles", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    private Set<RoleEntity> roles = new HashSet<>();

}

RoleEntity.java

package xyz.michaeltprojects.collchecklist.security.persistence;

import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

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

@Entity
@Table(name = "roles")
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
public class RoleEntity {

    @Id
    @GeneratedValue
    private UUID id;

    @Enumerated(EnumType.STRING)
    @Column(length = 20)
    private ERole name;

}

UserRepository.java

package xyz.michaeltprojects.collchecklist.security.persistence;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import java.util.Optional;
import java.util.UUID;

@Repository
public interface UserRepository extends JpaRepository<UserEntity, UUID> {

    Optional<UserEntity> findByEmail(String email);
    Boolean existsByUsername(String username);
    Boolean existsByEmail(String email);

}

Debug Output when calling findByEmail method

Database tables "user_roles" and "roles"

Answer 1

I had same issue and I could not get any values. When I used List instead of Set everything is fine.

I found out that there is a problem with hashcode and equals generated by Lombok. When I generated them manually everything works.

https://jpa-buddy.com/blog/lombok-and-jpa-what-may-go-wrong/

Answer 2

I had the same issue. In my case, I was using hibernate and liquibase to update the schema. After updating the schema with liquibase and inserting some data using liquibase, I could not get any associated value with manytomany relationship.

After changing Set to List. I was able to get values Like this

   @OneToMany(mappedBy = "user", fetch = FetchType.EAGER)
@OrderBy(value = "createdOn")
private Set<UserAppServices> userAppServices;

To

  @OneToMany(mappedBy = "user", fetch = FetchType.EAGER)
@OrderBy(value = "createdOn")
private List<UserAppServices> userAppServices;

Answer 3

Try to use List roles = new ArrayList<>()

In my code, I have used Set with ManyToMany relationship and I didn't get any associated vale after I changed the Set to List. I didn't understand Why the Set with hashSet didn't work.

Answer 4

I've somehow solved the issue... It seems that populating the relationships didn't work with UUIDs as identifiers. When I replaced them with longs it worked perfectly. Seems weird but it is like it is

Answer 5

You have to remove new HashSet<>(); from the user entity.

Answer 6

Can you try this? by adding an override function setRoles(..) below the UserEntity calss

package xyz.michaeltprojects.collchecklist.security.persistence;

import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

import javax.persistence.*;
import javax.validation.constraints.Email;
import javax.validation.constraints.NotBlank;
import javax.validation.constraints.Size;
import java.util.HashSet;
import java.util.Set;
import java.util.UUID;

@Entity
@Table(name = "users")
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
public class UserEntity {

    @Id
    @GeneratedValue
    private UUID id;

    @NotBlank
    @Size(min = 3, max = 30)
    private String username;

    @NotBlank
    @Size(min = 6, max = 50)
    @Email
    private String email;

    @NotBlank
    @Size(max = 120)
    private String password;

    @ManyToMany(fetch = FetchType.EAGER)
    @JoinTable(name = "user_roles", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    private Set<RoleEntity> roles = new HashSet<>();

   public UserEntity setRoles(final Set<RoleEntity> roles) {
     this.roles.clear();
     if (roles != null) {
         this.roles.addAll(roles);
     }
     return this;
   }

}

Answer 7

You ManyToMany is not correct, you need to reference the id of each table by using referencedColumnName

Take a look at this one:

@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinTable(name = "user_roles",
     joinColumns = @JoinColumn(name = "user_id", referencedColumnName = "id"),
     inverseJoinColumns = @JoinColumn(name = "role_id", referencedColumnName = "id"))
private Set<RoleEntity> roles;