2 Replies Latest reply on May 16, 2012 4:54 AM by Fabio Bozzo

    StackOverflowError when trying to explore a hierarchy

    Fabio Bozzo Newbie

      In my Jboss7 Java EE 6 web application, I need to manage a tree structure of simple "category" entities like that:

      @Entity
      @Table(name="categorie")
      @NamedQueries({
         
      @NamedQuery(name="selezionaTutti", query="select c from Categoria c left join fetch c.children left join fetch c.parent")
      })
      public class Categoria implements Serializable {

         
      private static final long serialVersionUID = 1L;

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

         
      @NotNull
         
      private String nome;

         
      @OneToMany(cascade=CascadeType.ALL,fetch=FetchType.EAGER)
         
      @JoinColumn(name = "parent_id")
         
      private List<Categoria> children = new LinkedList<Categoria>();

         
      @ManyToOne(fetch=FetchType.LAZY)
         
      @JoinColumn(name = "parent_id",insertable=false,updatable=false)
         
      private Categoria parent;

      ... //various getter, setter, and so on
      }

      The named query load my whole (little) tree all at a time, the first time, then it stays in the persistence context.

      Then I want to "explore" the tree, so I get the root node and pass it to this function:

      private List<Categoria> getAlberoCategorie(Categoria root, int profondita) {
             
      List<Categoria> tmpList = new ArrayList<Categoria>();
              root
      .setProfondita(profondita);
             
      if ( root.getParent() != null ) {
                  tmpList
      .add(root);
             
      }
             
      if (!root.getChildren().isEmpty()) {
                  profondita
      ++;
                 
      for (Categoria figlia : root.getChildren()) {
                      tmpList
      .addAll(getAlberoCategorie(figlia,profondita)); // this line generates the stack overflow!!!
                 
      }
             
      }
             
      return tmpList;
         
      }

      The exact stack trace of the exception is:

      java.lang.StackOverflowError org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:112) org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:137) org.hibernate.collection.internal.PersistentBag.isEmpty(PersistentBag.java:249) it.trew.data.CategoriaFacade.getAlberoCategorie(CategoriaFacade.java:59)

      In my local machine, all works fine indeed. On a small test server, it crashes when reading categories!

      How can I improve my function?