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Invokers allow you to customise how a particular method is executed. This is particular useful if your underlying service objects are not plain javabeans and instead need to be created or looked up via a custom factory. The following example illustrates how an invoker can be used to allow xfire to expose remote stateless session beans as a webservice. Given the method to invoke, this invoker will create a stateless session bean instance to invoke the method on. The same technique can be used to enable service calls to any object that requires custom creation/lookup. The invoker implementation is as follows: public class EJBInvoker implements Invoker { private EJBHome home; private Method createMethod; private static final Object[] EMPTY_OBJECT = new Object[0]; public EJBInvoker(EJBHome home) { this.home = home; try { if(!home.getEJBMetaData().isSession() || !home.getEJBMetaData().isStatelessSession()) { throw new IllegalArgumentException("home must be for a stateless session bean"); } createMethod = home.getClass().getMethod("create", new Class[0]); } catch(Exception ex) { throw new IllegalArgumentException("Unable to initialize invoker: " + ex); } } public Object invoke(Method m, Object[] params, MessageContext context) throws XFireFault { try { Object session = createMethod.invoke(home, EMPTY_OBJECT); return m.invoke(session, params); } catch(Exception ex) { throw new XFireFault("Error invoking ejb method " + m.getName(), ex, XFireFault.RECEIVER); } } } Invokers, once defined, need to be registered with the service binding. Once a handle onto a Service object has been obtained, the example invoker above can be registered on the binding like this: Service ejbService = ....; //look up the service from XFire, or create it ejbService.getBinding().setInvoker(new EJBInvoker(ejbHome)); |