001// Copyright 2005 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry.services.impl;
016
017import java.io.IOException;
018import java.io.Serializable;
019
020import org.apache.hivemind.util.Defense;
021import org.apache.tapestry.IRequestCycle;
022import org.apache.tapestry.engine.IEngineService;
023import org.apache.tapestry.engine.ILink;
024
025/**
026 * Outer proxy for engine services. The inner proxy resolves the engine service name to a engine
027 * service implementation and installed it into the outer proxy as a delegate. Although HiveMind
028 * does provide a similar system of inner and outer delegates, Tapestry's engine-service:
029 * {@link org.apache.tapestry.services.impl.EngineServiceObjectProvider} object provider can
030 * cause exceptions (recurive service build) when attempting to link two services together. This
031 * extra layer of proxying resolves that issue.
032 * 
033 * @author Howard M. Lewis Ship
034 * @since 4.0
035 */
036public class EngineServiceOuterProxy implements IEngineService, Serializable
037{
038    private final String _serviceName;
039
040    private IEngineService _delegate;
041
042    public EngineServiceOuterProxy(String serviceName)
043    {
044        Defense.notNull(serviceName, "serviceName");
045
046        _serviceName = serviceName;
047    }
048
049    void installDelegate(IEngineService delegate)
050    {
051        _delegate = delegate;
052    }
053
054    IEngineService getDelegate()
055    {
056        return _delegate;
057    }
058
059    public ILink getLink(boolean post, Object parameter)
060    {
061        return _delegate.getLink(post, parameter);
062    }
063
064    public void service(IRequestCycle cycle) throws IOException
065    {
066        _delegate.service(cycle);
067    }
068
069    public String getName()
070    {
071        return _serviceName;
072    }
073
074    public String toString()
075    {
076        return ImplMessages.engineServiceOuterProxyToString(_serviceName);
077    }
078
079}