Re: ValueProxy and cyclic dependencies lead to infinite loop

So basically I get a stackoverflow with these two exceptions. I have to stop/kill the server to stop them.

I think the problem is in ValueProxyCategory. It calls the function hashCode() and this calls AutoBeanUtils.getAllProperties(bean).hashCode(); This retrieves all properties as a Map and then calculates the hashcode for each element. However because I have a cyclic dependency between Term and Term2Term it will go into an infinite loop.

Caused by: java.lang.reflect.InvocationTargetException        at sun.reflect.GeneratedMethodAccessor88.invoke(Unknown Source)      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)      at java.lang.reflect.Method.invoke(Method.java:601)      at com.google.web.bindery.autobean.vm.impl.BeanMethod$5.invoke(BeanMethod.java:155)      at com.google.web.bindery.autobean.vm.impl.BeanMethod$1.invoke(BeanMethod.java:44)      at com.google.web.bindery.autobean.vm.impl.SimpleBeanHandler.invoke(SimpleBeanHandler.java:43)      at com.google.web.bindery.autobean.vm.impl.ShimHandler.hashCode(ShimHandler.java:66)      at sun.reflect.GeneratedMethodAccessor77.invoke(Unknown Source)      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)      at java.lang.reflect.Method.invoke(Method.java:601)      at com.google.web.bindery.autobean.vm.impl.ShimHandler.invoke(ShimHandler.java:76)      at java.util.HashMap$Entry.hashCode(HashMap.java:818)      at java.util.AbstractMap.hashCode(AbstractMap.java:494)      at com.google.web.bindery.requestfactory.shared.impl.ValueProxyCategory.hashCode(ValueProxyCategory.java:55)

On Wed, Nov 28, 2012 at 11:24 AM, Thomas Broyer <t.broyer@gmail.com> wrote:

Is there a "Caused by" for this UndeclaredThrowableException?

On Wednesday, November 28, 2012 10:41:34 AM UTC+1, Ümit Seren wrote:

I am not sure if this is a known issue. But I recently tried to map some JPA2 Entities to ValueProxy's and run into a weird issue.

In the database I have a table (Term) which references itself using an intermediate/mapping table (basically building a graph like structure).

Term ---> Term2Term.parent
Term <--- Term2Term.child

Basically a record from table A can have n childrin and exactly one parent (DAG).

The ValueProxy's look like this:

  @ProxyForName(value="xxxxx")  public interface TermProxy extends ValueProxy {      public Integer getId();      ......      public Set<Term2TermProxy> getParents();      public Set<Term2TermProxy> getChilds();  }

  @ProxyForName(value="xxxx")  public interface Term2TermProxy extends ValueProxy {        public Integer getId();      public TermProxy getParent();        public TermProxy getChild();    }

Furthermore I have an EntityProxy in which one Term is embedded:

  @ProxyForName(xxx)  public interface SomeEntityProxy extends EntityProxy{      TermProxy getTraitOntologyTerm();    }

When I load the SomeEntityProxy object and also load the TermProxy I run into an infinite loop on the backend/server when serializing the payload with following exception:

java.lang.reflect.UndeclaredThrowableException      at $Proxy118.hashCode(Unknown Source)      at com.google.web.bindery.autobean.vm.impl.ShimHandler.hashCode(ShimHandler.java:66)      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)      at java.lang.reflect.Method.invoke(Method.java:601)      at com.google.web.bindery.autobean.vm.impl.ShimHandler.invoke(ShimHandler.java:76)      at $Proxy118.hashCode(Unknown Source)      at java.util.HashMap.hash(HashMap.java:351)      at java.util.HashMap.put(HashMap.java:471)      at java.util.HashSet.add(HashSet.java:217)      at com.google.web.bindery.requestfactory.server.Resolver.resolveClientValue(Resolver.java:637)      at com.google.web.bindery.requestfactory.server.Resolver.access$400(Resolver.java:51)      at com.google.web.bindery.requestfactory.server.Resolver$PropertyResolver.visitReferenceProperty(Resolver.java:140)      at com.google.web.bindery.autobean.shared.AutoBeanVisitor.visitCollectionProperty(AutoBeanVisitor.java:229)      at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverseProperties(ProxyAutoBean.java:300)      at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.traverse(AbstractAutoBean.java:166)      at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.accept(AbstractAutoBean.java:101)      at com.google.web.bindery.requestfactory.server.Resolver.resolveClientValue(Resolver.java:414)

I suspect that this is due to the fact that ValueProxy's don't have an identity and on the backend it traverse through all properties of my entity. However by having a reference from Term2Term back to Term I can end up with a cyclic dependency.

i.e. Term A -> Term2Term.parent -> Term B -> Term2Term.child -> Term A

If I break one of the relationships (parent or child) from Term to Term2Term it serializes fine. However when I adda nother ValueProxy (Term A -> SomeValueProxy -> Term A ) that contains a property which maps back to the Term, I again get a stackoverflow however this time on the client.

I guess switching to EntityProxy would solve the problem as the properties don't automatically get serialized and for identity the stableId is used.

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