/** | |
* Copyright (C) 2010 Google, Inc. | |
* | |
* 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 com.google.inject.persist; | |
import com.google.inject.Inject; | |
import com.google.inject.Singleton; | |
import java.io.IOException; | |
import javax.servlet.Filter; | |
import javax.servlet.FilterChain; | |
import javax.servlet.FilterConfig; | |
import javax.servlet.ServletException; | |
import javax.servlet.ServletRequest; | |
import javax.servlet.ServletResponse; | |
/** | |
* Apply this filter to enable the HTTP Request unit of work and to have | |
* guice-persist manage the lifecycle of active units of work. | |
* The filter automatically starts and stops the relevant {@link PersistService} | |
* upon {@link javax.servlet.Filter#init(javax.servlet.FilterConfig)} and | |
* {@link javax.servlet.Filter#destroy()} respectively. | |
* | |
* <p> To be able to use the open session-in-view pattern (i.e. work per request), | |
* register this filter <b>once</b> in your Guice {@code ServletModule}. It is | |
* important that you register this filter before any other filter. | |
* | |
* For multiple providers, you should register this filter once per provider, inside | |
* a private module for each persist module installed (this must be the same private | |
* module where the specific persist module is itself installed). | |
* | |
* <p> | |
* Example configuration: | |
* <pre>{@code | |
* public class MyModule extends ServletModule { | |
* public void configureServlets() { | |
* filter("/*").through(PersistFilter.class); | |
* | |
* serve("/index.html").with(MyHtmlServlet.class); | |
* // Etc. | |
* } | |
* } | |
* }</pre> | |
* <p> | |
* This filter is thread safe and allows you to create injectors concurrently | |
* and deploy multiple guice-persist modules within the same injector, or even | |
* multiple injectors with persist modules withing the same JVM or web app. | |
* <p> | |
* This filter requires the Guice Servlet extension. | |
* | |
* @author Dhanji R. Prasanna (dhanji@gmail.com) | |
*/ | |
@Singleton | |
public final class PersistFilter implements Filter { | |
private final UnitOfWork unitOfWork; | |
private final PersistService persistService; | |
@Inject | |
public PersistFilter(UnitOfWork unitOfWork, PersistService persistService) { | |
this.unitOfWork = unitOfWork; | |
this.persistService = persistService; | |
} | |
public void init(FilterConfig filterConfig) throws ServletException { | |
persistService.start(); | |
} | |
public void destroy() { | |
persistService.stop(); | |
} | |
public void doFilter(final ServletRequest servletRequest, final ServletResponse servletResponse, | |
final FilterChain filterChain) throws IOException, ServletException { | |
unitOfWork.begin(); | |
try { | |
filterChain.doFilter(servletRequest, servletResponse); | |
} finally { | |
unitOfWork.end(); | |
} | |
} | |
} |