7 Replies Latest reply on Aug 9, 2007 7:47 AM by Sander Mak

    JavaAssist fails to create proxy

    Sander Mak Newbie

      My 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)