framework/src/net/sf/tapestry/engine/PageService.java

/*
 *  ====================================================================
 *  The Apache Software License, Version 1.1
 *
 *  Copyright (c) 2002 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 acknowledgment:
 *  "This product includes software developed by the
 *  Apache Software Foundation (http://www.apache.org/)."
 *  Alternately, this acknowledgment may appear in the software itself,
 *  if and wherever such third-party acknowledgments normally appear.
 *
 *  4. The names "Apache" and "Apache Software Foundation" and
 *  "Apache Tapestry" must not be used to endorse or promote products
 *  derived from this software without prior written permission. For
 *  written permission, please contact apache@apache.org.
 *
 *  5. Products derived from this software may not be called "Apache",
 *  "Apache Tapestry", nor may "Apache" appear in their name, without
 *  prior written permission of the Apache Software Foundation.
 *
 *  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 net.sf.tapestry.engine;

import java.io.IOException;

import javax.servlet.ServletException;

import net.sf.tapestry.ApplicationRuntimeException;
import net.sf.tapestry.Gesture;
import net.sf.tapestry.IComponent;
import net.sf.tapestry.IEngineService;
import net.sf.tapestry.IEngineServiceView;
import net.sf.tapestry.IPage;
import net.sf.tapestry.IRequestCycle;
import net.sf.tapestry.RequestContext;
import net.sf.tapestry.RequestCycleException;
import net.sf.tapestry.ResponseOutputStream;
import net.sf.tapestry.Tapestry;

/**
 *  Basic server for creating a link to another page in the application.
 *
 *  @author Howard Lewis Ship
 *  @version $Id$
 *  @since 1.0.9
 *
 **/

public class PageService extends AbstractService
{

    public Gesture buildGesture(IRequestCycle cycle, IComponent component, Object[] parameters)
    {
        if (Tapestry.size(parameters) != 1)
            throw new IllegalArgumentException(Tapestry.getString("service-single-parameter", PAGE_SERVICE));

        return assembleGesture(cycle, PAGE_SERVICE, (String[])parameters, null, true);

    }

    public boolean service(IEngineServiceView engine, IRequestCycle cycle, ResponseOutputStream output)
        throws RequestCycleException, ServletException, IOException
    {
        RequestContext context = cycle.getRequestContext();
        String[] serviceContext = getServiceContext(context);

        if (serviceContext == null || serviceContext.length != 1)
            throw new ApplicationRuntimeException(
                Tapestry.getString("service-single-parameter", IEngineService.PAGE_SERVICE));

        String pageName = serviceContext[0];

        // At one time, the page service required a session, but that is no longer necessary.
        // Users can now bookmark pages within a Tapestry application.  Pages
        // can implement validate() and throw a PageRedirectException if they don't
        // want to be accessed this way.  For example, most applications have a concept
        // of a "login" and have a few pages that don't require the user to be logged in,
        // and other pages that do.  The protected pages should redirect to a login page.

        IPage page = cycle.getPage(pageName);

        // Allow the page to validate that the user is allowed to visit.  This is simple
        // protection from malicious users who hack the URLs directly, or make inappropriate
        // use of the back button. 

        page.validate(cycle);

        cycle.setPage(page);

        engine.renderResponse(cycle, output);

        return true;
    }

    public String getName()
    {
        return PAGE_SERVICE;
    }

}