JavaAssist fails to create proxy
sammy8306 Aug 1, 2007 6:07 AMMy component:
package org.blog.weblayer.session; import org.jboss.seam.ScopeType; import org.jboss.seam.annotations.Scope; import org.jboss.seam.annotations.AutoCreate; import org.jboss.seam.annotations.Name; @Name("Sessiontag_st") @AutoCreate @Scope(ScopeType.SESSION) public class Var0 implements java.io.Serializable, weblayer.SessionVar<org.blog.domainmodel.Tag> { org.blog.domainmodel.Tag var = new org.blog.domainmodel.Tag(); public void setVar(org.blog.domainmodel.Tag var) { this.var = var; } public org.blog.domainmodel.Tag getVar() { return var; } }
The interface:
package weblayer; public interface SessionVar<T> { public T getVar(); public void setVar(T t); }
The lookup in another component:
((weblayer.SessionVar)Component.getInstance("Sessiontag_st")).setVar(t);
this line fails with:
org.jboss.seam.InstantiationException <snip> Caused by: java.lang.RuntimeException: duplicate method: getVar [java] at javassist.util.proxy.ProxyFactory.createClass(ProxyFactory.java:173) [java] at org.jboss.seam.Component.createProxyFactory(Component.java:1979) [java] at org.jboss.seam.Component.getProxyFactory(Component.java:1154) [java] at org.jboss.seam.Component.wrap(Component.java:1145) [java] at org.jboss.seam.Component.instantiateJavaBean(Component.java:1134) [java] at org.jboss.seam.Component.instantiate(Component.java:1088) [java] at org.jboss.seam.Component.newInstance(Component.java:1736) [java] ... 76 more [java] Caused by: javassist.CannotCompileException: duplicate method: getVar [java] at javassist.bytecode.ClassFile.testExistingMethod(ClassFile.java:544) [java] at javassist.bytecode.ClassFile.addMethod(ClassFile.java:528) [java] at javassist.util.proxy.ProxyFactory.override(ProxyFactory.java:373) [java] at javassist.util.proxy.ProxyFactory.overrideMethods(ProxyFactory.java:349) [java] at javassist.util.proxy.ProxyFactory.make(ProxyFactory.java:277) [java] at javassist.util.proxy.ProxyFactory.createClass(ProxyFactory.java:164) [java] ... 82 more
If I get rid of the interface on the session scoped component and cast to Var0 directly, everything works dandy... So, why can't my Seam component implement an interface?
(offtopic: originally I wanted to make Var0 parameterized, i.e. Var, assigning it different roles for each session var so that I do not need to write a specialization for each type I have, implementing a common generic interface. However, I really need the instantiation of the member field, which cannot be done by virtue of Java's type erasure scheme for generics)