/*
 * =============================================================================
 * 
 *   Copyright (c) 2007-2010, The JASYPT team (http://www.jasypt.org)
 * 
 *   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.jasypt.web.pbeconfig;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.jasypt.commons.CommonUtils;
import org.jasypt.exceptions.EncryptionInitializationException;

 ContextListener which takes a WebPBEInitializer implementation class name as a parameter (<context-param>) and calls its initializeWebPBEConfigs() method to allow the webapp to create its PBE encryptors and declare their associated WebPBEConfig objects. 

  An example web.xml fragment:

   <context-param>
     <param-name>webPBEInitializerClassName</param-name>
     <param-value>myapp.MyWebPBEInitializer</param-value>
   </context-param>
   <listener>
     <listener-class>
       org.jasypt.web.pbeconfig.WebPBEInitializationContextListener
     </listener-class>
   </listener>


  Important: If the web application uses Spring Framework, WebPBEConfig 
  objects are declared as beans in the Spring context and this Spring context
  is initialized at application deploy time 
  (with Spring's ContextLoaderListener), the use 
  of this context listener will become unnecessary.
 
Author:
Daniel Fernández
Since:
1.3/**
 * <p>
 *   ContextListener which takes a {@link WebPBEInitializer} implementation
 *   class name as a parameter (&lt;context-param>) and calls its
 *   <tt>initializeWebPBEConfigs()</tt> method to allow the webapp to
 *   create its PBE encryptors and declare their associated {@link WebPBEConfig}
 *   objects.
 * </p>
 * <p>
 *   An example <tt>web.xml</tt> fragment:
 * </p>
 * <pre>
 *    &lt;context-param>
 *      &lt;param-name>webPBEInitializerClassName&lt;/param-name>
 *      &lt;param-value>myapp.MyWebPBEInitializer&lt;/param-value>
 *    &lt;/context-param>
 *
 *    &lt;listener>
 *      &lt;listener-class>
 *        org.jasypt.web.pbeconfig.WebPBEInitializationContextListener
 *      &lt;/listener-class>
 *    &lt;/listener>
 * </pre>
 * <p>
 *   <b>Important</b>: If the web application uses Spring Framework, <tt>WebPBEConfig</tt> 
 *   objects are declared as beans in the Spring context and this Spring context
 *   is initialized at application deploy time 
 *   (with Spring's <tt>ContextLoaderListener</tt>), the use 
 *   of this context listener will become unnecessary.
 * </p> 
 * 
 * @since 1.3
 * 
 * @author Daniel Fern&aacute;ndez
 *
 */
public final class WebPBEInitializationContextListener 
        implements ServletContextListener {

    public static final String INIT_PARAM_INITIALIZER_CLASS_NAME = 
        "webPBEInitializerClassName"; 
    
    
    public void contextDestroyed(final ServletContextEvent sce) {
        // nothing to be done here
    }

    public void contextInitialized(final ServletContextEvent sce) {
        
        final String className = 
            sce.getServletContext().getInitParameter(
                    INIT_PARAM_INITIALIZER_CLASS_NAME);
        
        if (CommonUtils.isEmpty(className)) {
            throw new EncryptionInitializationException(
                    INIT_PARAM_INITIALIZER_CLASS_NAME + " context " +
                    "initialization parameter not set in web.xml");
        }

        Class initializerClass = null;
        try {
            initializerClass = 
                Thread.currentThread().getContextClassLoader().loadClass(className);
        } catch (ClassNotFoundException e) {
            throw new EncryptionInitializationException(e);
        }
        
        if (!WebPBEInitializer.class.isAssignableFrom(initializerClass)) {
            throw new EncryptionInitializationException("Class " + 
                    className + " does not implement interface " +
                    WebPBEInitializer.class.getName());
        }
        
        WebPBEInitializer initializer = null;
        try {
            initializer = 
                (WebPBEInitializer) initializerClass.newInstance();
        } catch (InstantiationException e) {
            throw new EncryptionInitializationException(e);
        } catch (IllegalAccessException e) {
            throw new EncryptionInitializationException(e);
        }

        // Let the user initialize his/her encryptors and WebPBEConfig objects.
        initializer.initializeWebPBEConfigs();
        
    }

    
    
}