/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you 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.apache.shiro.web.servlet;

 import org.apache.shiro.web.env.WebEnvironment;

 import org.apache.shiro.web.filter.mgt.FilterChainResolver;

 import org.apache.shiro.web.util.WebUtils;

 /**

  * Primary Shiro Filter for web applications configuring Shiro via Servlet <listener> in web.xml.

  * <p/>

  * As of Shiro 1.2, this is Shiro's preferred filter for {@code web.xml} configuration.  It expects the presence of a

  * Shiro {@link org.apache.shiro.web.env.WebEnvironment WebEnvironment} in the {@code ServletContext}, also

  * configured via {@code web.xml}.

  * <h2>Usage</h2>

  * As this Filter expects an available {@link org.apache.shiro.web.env.WebEnvironment WebEnvironment} instance to

  * be configured, it must be defined in {@code web.xml} with the companion

  * {@link org.apache.shiro.web.env.EnvironmentLoaderListener EnvironmentLoaderListener}, which performs the necessary

  * environment setup.  For example:

  * <pre>

  * <listener>

  *     <listener-class>{@link org.apache.shiro.web.env.EnvironmentLoaderListener}</listener-class>

  * </listener>

  * ...

  * <filter>

  *     <filter-name>ShiroFilter</filter-name>

  *     <filter-class>org.apache.shiro.web.servlet.ShiroFilter</filter-class>

  * </filter>

  *

  * <-- Filter all web requests.  This filter mapping is typically declared

  *     before all others to ensure any other filters are secured as well: -->

  * <filter-mapping>

  *     <filter-name>ShiroFilter</filter-name>

  *     <url-pattern>/*</url-pattern>

  * </filter-mapping>

  * </pre>

  * Configuration options (configuration file paths, etc) are specified as part of the

  * {@code EnvironmentLoaderListener} configuration.  See the

  * {@link org.apache.shiro.web.env.EnvironmentLoader EnvironmentLoader} JavaDoc for configuration options.

  *

  * @see org.apache.shiro.web.env.EnvironmentLoader EnvironmentLoader

  * @see org.apache.shiro.web.env.EnvironmentLoaderListener EnvironmentLoaderListener

  * @see <a href="http://shiro.apache.org/web.html">Apache Shiro Web Documentation</a>

  * @since 1.2

  */

 public class ShiroFilter extends AbstractShiroFilter {

     /**

      * Configures this instance based on the existing {@link org.apache.shiro.web.env.WebEnvironment} instance

      * available to the currently accessible {@link #getServletContext() servletContext}.

      *

      * @see org.apache.shiro.web.env.EnvironmentLoaderListener

      * @since 1.2

      */

     @Override

     public void init() throws Exception {

         WebEnvironment env = WebUtils.getRequiredWebEnvironment(getServletContext());

         setSecurityManager(env.getWebSecurityManager());

         FilterChainResolver resolver = env.getFilterChainResolver();

         if (resolver != null) {

             setFilterChainResolver(resolver);

         }

     }

 }