QueryException: A reference class must be provided

Question

I'm working on a program to organize my boredom. I started recently so I haven't began on the GUI yet. The program was working fine with videos/book but now that I added Game I get a queryException. Does someone know what I did wrong?

The error:

Caused by: Exception [EclipseLink-6029] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.QueryException Exception Description: A reference class must be provided.

The line where the error takes place:

public <E> List<E> getAll(Class<E> eClass){return manager.createQuery(manager.getCriteriaBuilder().createQuery(eClass)).getResultList(); }

Where the line gets called for the different entity types

for (Class eClass: Project.getAllItemTypes())
            repos.put(eClass, new Repository(persistenceAdministrator, eClass));

The Entity types

public static Class[] getAllItemTypes(){
        return new Class[]{Movie.class, TvShow.class, ComedyShow.class, Book.class, Comicbook.class, Manga.class, Game.class};
    }

The create-sql for Game and Task

CREATE TABLE Game(
    id INT NOT NULL AUTO_INCREMENT,
    stateStr VARCHAR(50) NOT NULL,
    title VARCHAR(100) NOT NULL,
    releaseDate DATE NOT NULL,
    gameId INT NULL,
  PRIMARY KEY (id),
  CONSTRAINT FK_gameId_game
    FOREIGN KEY (gameId)
    REFERENCES Game (id));

CREATE TABLE Task(
    id INT NOT NULL AUTO_INCREMENT,
    title VARCHAR(255) NOT NULL,
    completed BOOLEAN NOT NULL,
    gameId INT NOT NULL,
  PRIMARY KEY (id),
  CONSTRAINT FK_gameId_task
    FOREIGN KEY (gameId)
    REFERENCES Game (id));

Game Class:

@Entity
public class Game extends Item implements Serializable{

  @OneToMany
  private List<Game> children = new ArrayList<>();
  @OneToMany
  private List<Task> tasks = new ArrayList<>();
}

Item class

@MappedSuperclass
public abstract class Item extends IEntity implements Serializable{

   @Transient
    private State state;
    @Column(nullable=false)
    private String stateStr;
    @Basic(optional = false)
    @Column(name = "releaseDate")
    @Temporal(TemporalType.DATE)
    private Calendar releaseDate;
    @Column(nullable=false)
    private String title;

IEntity class

@MappedSuperclass
public abstract class IEntity extends Object implements Serializable{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

persistence.xml

score 1 · Answer 1 · answered May 29 '17 at 11:19

1

Normally the way you define the self-join is something like:

Game

@Entity
public class Game extends Item implements Serializable{

  @ManyToOne
  @JoinColumn(name = "gameId")
  private Game parent;

  @OneToMany(mappedBy = "parent")
  private List<Game> children = new ArrayList<>();

  @OneToMany(mappedBy = "game")
  private List<Task> tasks = new ArrayList<>();
}

Task

@Entity
public class Task{

    @ManyToOne
    @JoinColumn(name = "gameId")
    private Game game;
}

and dont forget that @ManyToOne mapping on the Task side.

answered May 29 '17 at 11:19

Maciej Kowalski

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Yeah, I've seen this before but I found it kinda weird to have the oneToMany and ManyToOne in the same class. But I'll try this and let you know, thanks for the answer. – Lennert Hofman May 29 '17 at 11:26
I get a ValidationException because the field game is seen as a non-entity. Caused by: Exception [EclipseLink-7250] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.ValidationException Exception Description: [class domain.Task] uses a non-entity [class domain.Game] as target entity in the relationship attribute [field game]. – Lennert Hofman May 29 '17 at 11:31
please add the Item class content. Also double check that you are using javax.persistence.Entity on the Game class – Maciej Kowalski May 29 '17 at 11:38
Added Item and IEntity class. These are the only imports from Game class so definitly right Entity: - import java.io.Serializable; - import java.util.*; - import javax.persistence.*; – Lennert Hofman May 29 '17 at 11:46
seems fine.. can you add the persistence.xml content – Maciej Kowalski May 29 '17 at 11:49
Added persistence.xml. PS can you use breakpoint/list in comment? – Lennert Hofman May 29 '17 at 11:52
add the IEntity and Item classes to the persistence.xml. As MappedSuperclasses they should be included as well – Maciej Kowalski May 29 '17 at 11:56
I can't add the mappedSuperclasses into persistence.xml. I posted a temporary picture. Maybe I could add them manually in the source, but I don't know if that's wise? – Lennert Hofman May 29 '17 at 12:01
yes try to edit manually and add those using the tag explicitly – Maciej Kowalski May 29 '17 at 12:04
I added them but get the same Error. – Lennert Hofman May 29 '17 at 12:06
remove the private int id; field from the Item class.. its already defined in the IEntity. Also if you set up the logger for your orm provider to debug.. is there any entry regarindg the Game entity which may be usefull? – Maciej Kowalski May 29 '17 at 12:14
I created a branch on gitHub, so you could see my full code if that would help. https://github.com/LHofman/unnamedProject1.0/tree/notWorking/unnamedProject1.0/src – Lennert Hofman May 29 '17 at 12:15
I already deleted the id field, I noticed it before. How would I set up the logger? I've never done that. – Lennert Hofman May 29 '17 at 12:19
another thing.. the fields in MappedSuperclasses should be proctected.. not private. – Maciej Kowalski May 29 '17 at 12:23
You're correct, but I don't think that's where the problem lies. It all worked perfectly without the Game class. – Lennert Hofman May 29 '17 at 12:27
do you still get validation exception or we are back to the original one? – Maciej Kowalski May 29 '17 at 12:34
Still ValidException. – Lennert Hofman May 29 '17 at 12:36
try to set up that logger.. https://wiki.eclipse.org/EclipseLink/Examples/JPA/Logging. Should shed some light on things.. – Maciej Kowalski May 29 '17 at 12:39
the problem was 1 line of java 8 lambda code in my Game class. (see answer) thanks anyway for helping me. – Lennert Hofman Jun 01 '17 at 14:34

score 0 · Accepted Answer · answered Jun 01 '17 at 14:33

I found the solution here

The problem was this method:

public boolean isCompleted(){
        //return tasks.stream().allMatch((task) -> task.isCompleted());
        for (Task task: tasks) if (!task.isCompleted()) return false;
        return true;
    }

Apparently JPA entity classes don't work so well with java 8 lambdas. I replaced the method with old school :P code and it works. Thanks anyway for helping me.

QueryException: A reference class must be provided

2 Answers2