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Subject: Re: MarshalledServiceItem
From: Gregg Wonderly <gregg@wonderly.org>
In-Reply-To: <4D45C8A5.6010309@zeus.net.au>
Date: Mon, 31 Jan 2011 19:29:47 -0600
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To: river-dev@incubator.apache.org
Sender: Gregg Wonderly <gregg@wonderly.org>

One of the important things for my use of my changes to the =
ServiceRegistrar interface was separating deserialization of the Entrys =
from the service object.  Ultimately, I wanted to not have to worry =
about how the "codebase" was structured in order to minimize =
downloading. Some Jini deployers have done things to put a small jar at =
the front of the codebase that just has the preferred.list in it.  Even =
that download, for me, would have been too much.  My customers' =
deployments have nearly 50 codebases visible when my client starts up.  =
Those 50 connections over a cellular or other high latency network would =
make service selection take way too long.

Being able to defer downloading was also controlled by the changes to =
ClassLoading to include the "neverPrefer" settings on a class name.  I =
can do that now through the recent RMIClassLoaderSPI override =
capabilities.  But I still need to be able to control which Entry is =
deserialized.  I need to be able to ask what classes, by name, are in =
the namespace of each Entry object as my implementation allowed. I had =
made changes to Reggie marshalling to use reflection to get the class =
hierarchy, and then provided access to the list of classnames as part of =
the returned, marshalled value in my API.

Gregg Wonderly

On Jan 30, 2011, at 2:23 PM, Peter Firmstone wrote:

> Gut feel, tells me the following class is not right, it's intent is to =
provide an api for implementation of delayed unmarshalling and =
provisioning of codebases, for services implementing a lookup service or =
ServiceRegistrar, whilst retaining backward compatibility.
>=20
> In other words, the lookup service proxy would implement it.
>=20
> Thoughts I had were to declare IOException's on methods, and to return =
a String annotation, rather than a URI.
>=20
> What are your thoughts?
>=20
> Cheers,
>=20
> Peter.
>=20
> /*
> * Licensed to the Apache Software Foundation (ASF) under one
> * or more contributor license agreements.  See the NOTICE file
> * distributed with this work for additional information
> * regarding copyright ownership. The ASF licenses this file
> * to you under the Apache License, Version 2.0 (the
> * "License"); you may not use this file except in compliance
> * with the License. You may obtain a copy of the License at
> *
> *      http://www.apache.org/licenses/LICENSE-2.0
> *
> * Unless required by applicable law or agreed to in writing, software
> * distributed under the License is distributed on an "AS IS" BASIS,
> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or =
implied.
> * See the License for the specific language governing permissions and
> * limitations under the License.
> */
>=20
> package org.apache.river.api.lookup;
>=20
> import java.net.URI;
> import java.security.CodeSource;
> import net.jini.core.entry.Entry;
> import net.jini.core.lookup.ServiceID;
> import net.jini.core.lookup.ServiceItem;
>=20
> /**
> * MarshalledServiceItem extends ServiceItem and can be used anywhere a
> * ServiceItem can.  A MarshalledServiceItem implementation instance
> * contains the marshalled form of a Service and it's Entry's,
> * the corresponding superclass ServiceItem however contains null =
values
> * for the service and can exclude any Entry's, however where Entry
> * classes already exist at the client, that they be unmarshalled.
> *
> * The ServiceID shall be in unmarshalled form always in the =
ServiceItem super class.
> *
> * Since the ServiceItem.service is null, use of this class in existing =
software
> * will not return the service, however it will not break that software =
as
> * ServiceItem's contract is to set service or Entry's to null when =
they cannot
> * be unmarshalled.
> *
> * ServiceItem's toString() method will return a different result for
> * MarshalledServiceItem instances.
> *
> * If required, a new ServiceItem that is fully unmarshalled
> * can be constructed from this class's methods and ServiceID.
> *
> * @author Peter Firmstone.
> */
> public abstract class MarshalledServiceItem extends ServiceItem{
>   private static final long SerialVersionUID =3D 1L;
>   protected MarshalledServiceItem(ServiceID id, Entry[] =
unmarshalledEntries){
>       super(id, (Object) null, unmarshalledEntries);
>   }
>   /**
>    * Unmarshall the service proxy.
>    * @param load service with local or existing CodeSource or null for
>    * default.
>    * @return the service proxy, null if class not found.
>    */
>   public abstract Object getService(CodeSource[] code);
>   /**
>    * Unmarshall the Entry's
>    * @return array of Entry's, null entry in array for any class not =
found.
>    */
>   public abstract Entry[] getEntries();
>     public abstract URI[] getAnnotations();
> }
>=20