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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