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}