scala hibernate/jpa - ignore autogenerated bitmap$init$0 mapping

Question

Trying to use hibernate/jpa with scala. Running into interesting issue.

This is my entity definition.

@Entity
class Product(n: String, d: Double) ext         


        

Answer 1

Found a couple of interesting things about this issue.

I have this Model class in my application:

@Entity
@Table(name="users")
class User extends Model{
  @Id
  @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="users_id_seq")
  @Column(name="id", updatable=false, nullable=false)
  val id:Long = 0L

  @BeanProperty var name:String = _
  @BeanProperty var email:String = _ 

}

This class is compiled to a java class named User, which in turn is defined like this:

@Entity
@Table(name="users")
@ScalaSignature(bytes=long array of bytes)
public class User extends Model
   implements ScalaObject, EntityBean
{

   @Id
   @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="users_id_seq")
   @Column(name="id", updatable=false, nullable=false)
   private final long id;
   private String name;
   private String email;
   private volatile int bitmap$init$0;
   private static String _EBEAN_MARKER = "models.User";

   ...

   public long id()
  {
    if ((_ebean_get_bitmap$init$0() & 0x1) != 0)
    {
        _ebean_get_id(); return _ebean_get_id(); 
   } 
   throw new 
         UninitializedFieldError("Uninitialized field: User.scala: 17".toString());
    }

   public String name()
   {
   if ((_ebean_get_bitmap$init$0() & 0x2) != 0)
   {
     _ebean_get_name(); return _ebean_get_name();
   } throw new 
           UninitializedFieldError("Uninitialized field: User.scala: 19".toString()); 
   } 

   public void name_$eq(String paramString) { 
     _ebean_set_name(paramString); 
      _ebean_set_bitmap$init$0(_ebean_get_bitmap$init$0() | 0x2);
   }

  ....

The bitmap$init$0 actually comes from a class enhancement, and I thought that the responsible was the Ebean library, which I'm currently using. But after reading your post I went to investigate if JPA itself was doing some sort of bytecode enhancement on this object. In order to check this out, I created a copy project, but in Java. The generated code for the User class happens to have no bitmap$init$0 field, as follow:

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

@Entity
@Table(name="users")
public class User
{

  @Id
  @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="users_id_seq")
  @Column(name="id", updatable=false, nullable=false)
  private Long id;
  private String name;
  private String email;

 public void setId(Long id)
 {
    this.id = id;
 }

 public Long getId() {
   return this.id;
 }

public String getName() {
   return this.name;
 }
 public void setName(String name) {
   this.name = name;
 }
 public String getEmail() {
    return this.email;
 }
 public void setEmail(String email) {
    this.email = email;
  }
}

All this kind of trouble led me to this post and I most certainly agree. It seems that integrating JPA to Scala Ebean/Hibernate is kind of a real pain. I still didn't understand if this bitmap$ini$0 field in injected to the class bytecode by Ebean or something else.

It seems that you can try to bypass this kind of behavior by associating an annotation (@Transitent) to the generated Java bytecode, by compiling the code first for java then to Scala, something similar to what is described here. But I really don't think that's really worthy!

Answer 2

I don't know where that autogenerated field is coming from, but you could try to streamline your class to have less fields:

@Entity
class Product(var name: String = "", var price: Double = 0) extends EntityBase {

  @ManyToOne
  @JoinColumn(name="orderId")
  var order: Order = _

  override def toString = "Product: " + id + " " + name
}