/*
* Copyright 2005 Joe Walker
*
* Licensed 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.
*/
package org.directwebremoting.ui;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.WebContext;
import org.directwebremoting.WebContextFactory;
/**
* A way to call functions in JavaScript that return data using a reverse ajax
* proxy.
* @author Joe Walker [joe at getahead dot ltd dot uk]
*/
public abstract class Callback<T>
{
/**
* Create a Callback from a DWR thread,
* i.e. where {@link WebContextFactory#get()} =! null
*/
public Callback()
{
WebContext context = WebContextFactory.get();
if (context == null)
{
throw new IllegalStateException("Attempt to use Callback without any ScriptSessions, from a non DWR thread. There is nowhere for replies to go.");
}
sessions.add(context.getScriptSession());
}
/**
* Used when you need to specify the browser that will be providing the
* response
* @param session The browser to answer the question
*/
public Callback(ScriptSession session)
{
sessions.add(session);
}
/**
* Used when you need to specify a group of browsers that will be providing
* the responses. The callback will be executed once per browser that
* replies.
* @param sessionList The browsers to answer the question
*/
public Callback(Collection<ScriptSession> sessionList)
{
sessions.addAll(sessionList);
}
/**
* A browser has completed some remote call as has data for you
* @param data The data returned by the browser
*/
public abstract void dataReturned(T data);
/**
* Accessor for the ScriptSessions that will reply to the question.
* This method is generally for DWR internal use, but only because it's
* unlikely to be useful to others.
* @return An immutable list of browsers that may reply to the question.
*/
public Collection<ScriptSession> getScriptSessions()
{
return Collections.unmodifiableCollection(sessions);
}
/**
* We store the ScriptSessions that we send replies to, here.
*/
private final List<ScriptSession> sessions = new ArrayList<ScriptSession>();
}