/*
* Copyright 1999-2004 The Apache Software Foundation
*
* 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.apache.commons.chain.web.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.chain.Catalog;
import org.apache.commons.chain.CatalogFactory;
import org.apache.commons.chain.Command;
import org.apache.commons.chain.web.ChainServlet;
/**
* <p>Custom subclass of {@link ChainServlet} that also dispatches incoming
* requests to a configurable {@link Command} loaded from the specified
* {@link Catalog}.</p>
*
* <p>In addition to the <em>servlet</em> init parameters supported by
* {@link ChainServlet}, this class supports the following additional
* parameters:</p>
* <ul>
* <li><strong>org.apache.commons.chain.CATALOG</strong> - Name of the
* catalog from which to acquire commands to be executed. If not
* specified, the default catalog for this application will be used.</li>
* <li><strong>org.apache.commons.chain.COMMAND</strong> - Name of the
* {@link Command} (looked up in our configured {@link Catalog} used
* to process all incoming servlet requests. If not specified,
* defaults to <code>command</code>.</li>
* </ul>
*
* <p>Also, the <code>org.apache.commons.chain.CONFIG_ATTR</code>
* init parameter is also used to identify the {@link Context} attribute under
* which our configured {@link Catalog} will be made available to
* {@link Command}s processing our requests, in addition to its definition
* of the <code>ServletContext</code> attribute key under which the
* {@link Catalog} is available.</p>
*/
public class ChainProcessor extends ChainServlet {
// ------------------------------------------------------ Manifest Constants
/**
* <p>The name of the servlet init parameter containing the name of the
* {@link Catalog} to use for processing incoming requests.</p>
*/
public static final String CATALOG =
"org.apache.commons.chain.CATALOG";
/**
* <p>The default request attribute under which we expose the
* {@link Catalog} being used to subordinate {@link Command}s.</p>
*/
public static final String CATALOG_DEFAULT =
"org.apache.commons.chain.CATALOG";
/**
* <p>The name of the servlet init parameter containing the name of the
* {@link Command} (loaded from our configured {@link Catalog} to use
* for processing each incoming request.</p>
*/
public static final String COMMAND =
"org.apache.commons.chain.COMMAND";
/**
* <p>The default command name.</p>
*/
private static final String COMMAND_DEFAULT = "command";
// ------------------------------------------------------ Instance Variables
/**
* <p>The name of the context attribute under which our {@link Catalog}
* is stored. This value is also used as the name of the
* context attribute under which the catalog is exposed to commands.
* If not specified, we will look up commands in the appropriate
* {@link Catalog} retrieved from our {@link CatalogFactory}.</p>
*/
private String attribute = null;
/**
* <p>The name of the {@link Catalog} to retrieve from the
* {@link CatalogFactory} for this application, or <code>null</code>
* to select the default {@link Catalog}.</p>
*/
private String catalog = null;
/**
* <p>The name of the {@link Command} to be executed for each incoming
* request.</p>
*/
private String command = null;
/**
* <p>The {@link CatalogFactory} for this application.</p>
*/
private CatalogFactory factory = null;
// --------------------------------------------------------- Servlet Methods
/**
* <p>Clean up as this application is shut down.</p>
*/
public void destroy() {
super.destroy();
attribute = null;
catalog = null;
command = null;
factory = null;
}
/**
* <p>Cache the name of the command we should execute for each request.</p>
*
* @exception ServletException if an initialization error occurs
*/
public void init() throws ServletException {
super.init();
attribute = getServletConfig().getInitParameter(CONFIG_ATTR);
catalog = getServletConfig().getInitParameter(CATALOG);
command = getServletConfig().getInitParameter(COMMAND);
if (command == null) {
command = COMMAND_DEFAULT;
}
factory = CatalogFactory.getInstance();
}
/**
* <p>Configure a {@link ServletWebContext} for the current request, and
* pass it to the <code>execute()</code> method of the specified
* {@link Command}, loaded from our configured {@link Catalog}.</p>
*
* @param request The request we are processing
* @param response The response we are creating
*
* @exception IOException if an input/output error occurs
* @exception ServletException if a servlet exception occurs
*/
public void service(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException {
ServletWebContext context =
new ServletWebContext(getServletContext(), request, response);
Catalog theCatalog = null;
if (attribute != null) {
theCatalog = (Catalog) getServletContext().getAttribute
(this.attribute);
} else if (catalog != null) {
theCatalog = factory.getCatalog(catalog);
} else {
theCatalog = factory.getCatalog();
}
if (attribute == null) {
request.setAttribute(CATALOG_DEFAULT, theCatalog);
}
Command command = theCatalog.getCommand(this.command);
try {
command.execute(context);
} catch (Exception e) {
throw new ServletException(e);
}
}
}