1 /* 2 * Copyright (C) 2010 Google, Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.inject.persist; 18 19 import com.google.inject.Inject; 20 import com.google.inject.Singleton; 21 import java.io.IOException; 22 import javax.servlet.Filter; 23 import javax.servlet.FilterChain; 24 import javax.servlet.FilterConfig; 25 import javax.servlet.ServletException; 26 import javax.servlet.ServletRequest; 27 import javax.servlet.ServletResponse; 28 29 /** 30 * Apply this filter to enable the HTTP Request unit of work and to have guice-persist manage the 31 * lifecycle of active units of work. The filter automatically starts and stops the relevant {@link 32 * PersistService} upon {@link javax.servlet.Filter#init(javax.servlet.FilterConfig)} and {@link 33 * javax.servlet.Filter#destroy()} respectively. 34 * 35 * <p>To be able to use the open session-in-view pattern (i.e. work per request), register this 36 * filter <b>once</b> in your Guice {@code ServletModule}. It is important that you register this 37 * filter before any other filter. 38 * 39 * <p>For multiple providers, you should register this filter once per provider, inside a private 40 * module for each persist module installed (this must be the same private module where the specific 41 * persist module is itself installed). 42 * 43 * <p>Example configuration: 44 * 45 * <pre>{@code 46 * public class MyModule extends ServletModule { 47 * public void configureServlets() { 48 * filter("/*").through(PersistFilter.class); 49 * 50 * serve("/index.html").with(MyHtmlServlet.class); 51 * // Etc. 52 * } 53 * } 54 * }</pre> 55 * 56 * <p>This filter is thread safe and allows you to create injectors concurrently and deploy multiple 57 * guice-persist modules within the same injector, or even multiple injectors with persist modules 58 * withing the same JVM or web app. 59 * 60 * <p>This filter requires the Guice Servlet extension. 61 * 62 * @author Dhanji R. Prasanna (dhanji (at) gmail.com) 63 */ 64 @Singleton 65 public final class PersistFilter implements Filter { 66 private final UnitOfWork unitOfWork; 67 private final PersistService persistService; 68 69 @Inject 70 public PersistFilter(UnitOfWork unitOfWork, PersistService persistService) { 71 this.unitOfWork = unitOfWork; 72 this.persistService = persistService; 73 } 74 75 @Override 76 public void init(FilterConfig filterConfig) throws ServletException { 77 persistService.start(); 78 } 79 80 @Override 81 public void destroy() { 82 persistService.stop(); 83 } 84 85 @Override 86 public void doFilter( 87 final ServletRequest servletRequest, 88 final ServletResponse servletResponse, 89 final FilterChain filterChain) 90 throws IOException, ServletException { 91 92 unitOfWork.begin(); 93 try { 94 filterChain.doFilter(servletRequest, servletResponse); 95 } finally { 96 unitOfWork.end(); 97 } 98 } 99 } 100
