craigmcc 01/09/03 19:56:51
Added: workflow/src/java/org/apache/commons/workflow/web
ActivityServlet.java
Log:
Add an example servlet demonstrating one way to integrate workflow
processing into a web application. The theory of operation is that you
will create a servlet definition (using this servlet class), and one or
more servlet mappings, for each workflow Activity that is supported by
your web application.
Revision Changes Path
1.1
jakarta-commons-sandbox/workflow/src/java/org/apache/commons/workflow/web/ActivityServlet.java
Index: ActivityServlet.java
===================================================================
/*
* $Header:
/home/cvs/jakarta-commons-sandbox/workflow/src/java/org/apache/commons/workflow/web/ActivityServlet.java,v
1.1 2001/09/04 02:56:51 craigmcc Exp $
* $Revision: 1.1 $
* $Date: 2001/09/04 02:56:51 $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 1999-2001 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [EMAIL PROTECTED]
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Group.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package org.apache.commons.workflow.web;
import java.io.InputStream;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.commons.digester.Digester;
import org.apache.commons.workflow.Activity;
import org.apache.commons.workflow.StepException;
import org.apache.commons.workflow.base.BaseRuleSet;
import org.apache.commons.workflow.core.CoreRuleSet;
import org.apache.commons.workflow.io.IoRuleSet;
import org.apache.commons.workflow.web.WebContext;
import org.apache.commons.workflow.web.WebRuleSet;
/**
* <p>Demonstration servlet that illustrates how workflow support can be
* integrated into web applications (or web services) without any
* dependencies on application frameworks. A servlet <em>definition</em>
* (plus one or more servlet <em>mappings</em>) will be associated with
* each <code>Activity</code> supported by a particular web application.</p>
*
* <p>The following servlet initialization parameters are supported, with
* default values in square brackets):</p>
* <ul>
* <li><strong>activity</strong> - Context-relative resource path to the
* definition file for the <code>Activity</code> that is supported by
* this servlet definition.</li>
* <li><strong>attribute</strong> - Session attribute name under which our
* current <code>Context</code> instance is stored.
* [org.apache.commons.workflow.web.CONTEXT]</li>
* </ul>
*
* @author Craig R. McClanahan
* @version $Revision: 1.1 $ $Date: 2001/09/04 02:56:51 $
*/
public class ActivityServlet extends HttpServlet {
// ----------------------------------------------------- Instance Variables
/**
* The <code>Activity</code> that is supported by this servlet definition.
*/
protected Activity activity = null;
/**
* Name of the session attribute for our current <code>Context</code>.
*/
protected String attribute = "org.apache.commons.workflow.web.CONTEXT";
// --------------------------------------------------------- Public Methods
/**
* Perform graceful shutdown of this servlet definition.
*/
public void destroy() {
; // No processing required
}
/**
* Process a GET transaction.
*
* @param request The servlet request we are processing
* @param response The servlet response we are processing
*
* @exception IOException if an input/output error occurs
* @exception ServletException if a servlet exception occurs
*/
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException {
doPost(request, response);
}
/**
* Process a POST transaction.
*
* @param request The servlet request we are processing
* @param response The servlet response we are processing
*
* @exception IOException if an input/output error occurs
* @exception ServletException if a servlet exception occurs
*/
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException {
// Acquire or create the current Context for this user
HttpSession session = request.getSession(true);
WebContext context = (WebContext)
session.getAttribute(attribute);
if (context == null) {
context = new WebContext();
context.setActivity(activity);
context.setHttpSession(session);
context.setServletContext(getServletContext());
session.setAttribute(attribute, context);
}
// If we are not already executing our associated Activity, call it
// (to facilitate nesting by simply linking to the URI associated
// with a different activity)
if (!activity.equals(context.getActivity()))
context.call(activity);
// Execute our activity until suspended or completed (synchronized
// to avoid race conditions in framed environments, or other situations
// where multiple simultaneous requests might be active)
synchronized (context) {
context.setServletRequest(request);
context.setServletResponse(response);
try {
context.execute();
} catch (StepException e) {
if (e.getCause() == null)
throw new ServletException(e.getMessage(), e);
else
throw new ServletException(e.getMessage(), e.getCause());
}
}
}
/**
* Perform graceful startup of this servlet definition.
*
* @exception ServletException if we cannot process the activity
* definition file for this activity
*/
public void init() throws ServletException {
// Record the session attribute name for our current Context
String value = getServletConfig().getInitParameter("attribute");
if (value != null)
attribute = value;
// Parse the activity definition resource for our Activity
String path = getServletConfig().getInitParameter("activity");
if (path == null)
throw new UnavailableException
("Must specify an 'activity' initialization parameter");
parse(path);
if (activity == null)
throw new UnavailableException("No activity defined in resource " +
path);
}
/**
* Set the <code>Activity</code> associated with this instance.
*
* @param activity The new associated Activity
*/
public void setActivity(Activity activity) {
this.activity = activity;
}
// ------------------------------------------------------ Protected Methods
/**
* Parse the activity definition resource for this servlet definition.
*
* @param path Context-relative resource path of the activity definition
* resource
*
* @exception ServletException on any processing error during parsing
*/
protected void parse(String path) throws ServletException {
// Get an input source for the specified resource path
InputStream is =
getServletContext().getResourceAsStream(path);
if (is == null)
throw new UnavailableException("Cannot access resource " +
path);
// Configure a Digester instance to parse our activity definition
Digester digester = new Digester();
digester.setDebug(999);
digester.setNamespaceAware(true);
digester.setValidating(false);
digester.push(this);
// Add rules to recognize the built-in Steps that we know about
BaseRuleSet brs = new BaseRuleSet();
digester.addRuleSet(brs);
digester.addRuleSet(new CoreRuleSet());
digester.addRuleSet(new IoRuleSet());
digester.addRuleSet(new WebRuleSet());
// Add a rule to register the Activity being created
digester.setRuleNamespaceURI(brs.getNamespaceURI());
digester.addSetNext("activity", "setActivity",
"org.apache.commons.workflow.Activity");
// Parse the activity definition
try {
digester.parse(is);
} catch (Throwable t) {
log("Cannot parse resource " + path, t);
throw new UnavailableException("Cannot parse resource " + path);
} finally {
try {
is.close();
} catch (Throwable u) {
;
}
}
}
}
