/* Copyright 2004, 2005, 2006 Acegi Technology Pty Limited

  *

  * 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.acegisecurity.util;

 import org.springframework.beans.factory.BeanFactoryUtils;

 import org.springframework.context.ApplicationContext;

 import org.springframework.web.context.support.WebApplicationContextUtils;

 import java.io.IOException;

 import java.util.Map;

 import javax.servlet.Filter;

 import javax.servlet.FilterChain;

 import javax.servlet.FilterConfig;

 import javax.servlet.ServletContext;

 import javax.servlet.ServletException;

 import javax.servlet.ServletRequest;

 import javax.servlet.ServletResponse;

 /**

  * <p>Delegates <code>Filter</code> requests to a Spring-managed bean.</p>

  *

  * <p>This class acts as a proxy on behalf of a

  * target <code>Filter</code> that is defined in the Spring bean context. It is necessary to specify which target

  * <code>Filter</code> should be proxied as a filter initialization parameter.</p>

  *

  * <p>On filter initialisation, the class will use Spring's {@link

  * WebApplicationContextUtils#getWebApplicationContext(ServletContext sc)} method to obtain an

  * <code>ApplicationContext</code> instance. It will expect to find the target <code>Filter</code> in this

  * <code>ApplicationContext</code>.</p>

  *

  * <p>To use this filter, it is necessary to specify <b>one</b> of the following filter initialization parameters:

  *  <ul>

  *      <li><code>targetClass</code> indicates the class of the target <code>Filter</code> defined in the bean

  *      context. The only requirements are that this target class implements the <code>javax.servlet.Filter</code>

  *      interface and at least one instance is available in the <code>ApplicationContext</code>.</li>

  *      <li><code>targetBean</code> indicates the bean name of the target class.</li>

  *  </ul>

  * If both initialization parameters are specified, <code>targetBean</code> takes priority.</p>

  *

  * <p>An additional

  * initialization parameter, <code>init</code>, is also supported. If set to "<code>lazy</code>" the initialization

  * will take place on the first HTTP request, rather than at filter creation time. This makes it possible to use

  * <code>FilterToBeanProxy</code> with the Spring <code>ContextLoaderServlet</code>. Where possible you should not use

  * this initialization parameter, instead using <code>ContextLoaderListener</code>.</p>

  *

  * <p>A final optional initialization parameter, <code>lifecycle</code>, determines whether the servlet container

  * or the IoC container manages the lifecycle of the proxied filter. When possible you should write your filters to be

  * managed via the IoC container interfaces such as {@link org.springframework.beans.factory.InitializingBean} and

  * {@link org.springframework.beans.factory.DisposableBean}. If you cannot control the filters you wish to proxy (eg

  * you do not have their source code) you might need to allow the servlet container to manage lifecycle via the {@link

  * javax.servlet.Filter#init(javax.servlet.FilterConfig)} and {@link javax.servlet.Filter#destroy()} methods. If this

  * case, set the <code>lifecycle</code> initialization parameter to <code>servlet-container-managed</code>. If the

  * parameter is any other value, servlet container lifecycle methods will not be delegated through to the proxy.</p>

  *

  * @author Ben Alex

  * @version $Id: FilterToBeanProxy.java 1784 2007-02-24 21:00:24Z luke_t $

  */

 public class FilterToBeanProxy implements Filter {

     //~ Instance fields ================================================================================================

     private Filter delegate;

     private FilterConfig filterConfig;

     private boolean initialized = false;

     private boolean servletContainerManaged = false;

     //~ Methods ========================================================================================================

     public void destroy() {

         if ((delegate != null) && servletContainerManaged) {

             delegate.destroy();

         }

     }

     public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

         throws IOException, ServletException {

         if (!initialized) {

             doInit();

         }

         delegate.doFilter(request, response, chain);

     }

     private synchronized void doInit() throws ServletException {

         if (initialized) {

             // already initialized, so don't re-initialize

             return;

         }

         String targetBean = filterConfig.getInitParameter("targetBean");

         if ("".equals(targetBean)) {

             targetBean = null;

         }

         String lifecycle = filterConfig.getInitParameter("lifecycle");

         if ("servlet-container-managed".equals(lifecycle)) {

             servletContainerManaged = true;

         }

         ApplicationContext ctx = this.getContext(filterConfig);

         String beanName = null;

         if ((targetBean != null) && ctx.containsBean(targetBean)) {

             beanName = targetBean;

         } else if (targetBean != null) {

             throw new ServletException("targetBean '" + targetBean + "' not found in context");

         } else {

             String targetClassString = filterConfig.getInitParameter("targetClass");

             if ((targetClassString == null) || "".equals(targetClassString)) {

                 throw new ServletException("targetClass or targetBean must be specified");

             }

             Class targetClass;

             try {

                 targetClass = Thread.currentThread().getContextClassLoader().loadClass(targetClassString);

             } catch (ClassNotFoundException ex) {

                 throw new ServletException("Class of type " + targetClassString + " not found in classloader");

             }

             Map beans = BeanFactoryUtils.beansOfTypeIncludingAncestors(ctx, targetClass, true, true);

             if (beans.size() == 0) {

                 throw new ServletException("Bean context must contain at least one bean of type " + targetClassString);

             }

             beanName = (String) beans.keySet().iterator().next();

         }

         Object object = ctx.getBean(beanName);

         if (!(object instanceof Filter)) {

             throw new ServletException("Bean '" + beanName + "' does not implement javax.servlet.Filter");

         }

         delegate = (Filter) object;

         if (servletContainerManaged) {

             delegate.init(filterConfig);

         }

         // Set initialized to true at the end of the synchronized method, so

         // that invocations of doFilter() before this method has completed will not

         // cause NullPointerException

         initialized = true;

     }

     /**

      * Allows test cases to override where application context obtained from.

      *

      * @param filterConfig which can be used to find the <code>ServletContext</code>

      *

      * @return the Spring application context

      */

     protected ApplicationContext getContext(FilterConfig filterConfig) {

         return WebApplicationContextUtils.getRequiredWebApplicationContext(filterConfig.getServletContext());

     }

     public void init(FilterConfig filterConfig) throws ServletException {

         this.filterConfig = filterConfig;

         String strategy = filterConfig.getInitParameter("init");

         if ((strategy != null) && strategy.toLowerCase().equals("lazy")) {

             return;

         }

         doInit();

     }

 }