Infinite Recursion with Jackson JSON and Hibernate JPA issue

Question

When trying to convert a JPA object that has a bi-directional association into JSON, I keep getting

org.codehaus.jackson.map.JsonMappingException: Infinite          


        

Answer 1

I had this problem, but I didn't want to use annotation in my entities, so I solved by creating a constructor for my class, this constructor must not have a reference back to the entities who references this entity. Let's say this scenario.

public class A{
   private int id;
   private String code;
   private String name;
   private List bs;
}

public class B{
   private int id;
   private String code;
   private String name;
   private A a;
}

If you try to send to the view the class B or A with @ResponseBody it may cause an infinite loop. You can write a constructor in your class and create a query with your entityManager like this.

"select new A(id, code, name) from A"

This is the class with the constructor.

public class A{
   private int id;
   private String code;
   private String name;
   private List bs;

   public A(){
   }

   public A(int id, String code, String name){
      this.id = id;
      this.code = code;
      this.name = name;
   }

}

However, there are some constrictions about this solution, as you can see, in the constructor I did not make a reference to List bs this is because Hibernate does not allow it, at least in version 3.6.10.Final, so when I need to show both entities in a view I do the following.

public A getAById(int id); //THE A id

public List getBsByAId(int idA); //the A id.

The other problem with this solution, is that if you add or remove a property you must update your constructor and all your queries.