ASF_20_SRC_AUTO/src/blocks/portal/java/org/apache/cocoon/portal/transformation/NewEventLinkTransformer.java

/*
 * Copyright 1999-2002,2004 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.cocoon.portal.transformation;

import java.util.Stack;

import org.apache.avalon.framework.service.ServiceException;
import org.apache.cocoon.portal.PortalService;
import org.apache.cocoon.portal.coplet.CopletInstanceData;
import org.apache.cocoon.portal.event.impl.CopletLinkEvent;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.AttributesImpl;

/**
 * This transformer ist used to replace links (URIs) from elements
 * like <a href="URI"> or <form action="URI"> with portal
 * event uris. Therefore the transformer searches for <eventlink>
 * elements replaces the URI form the attribute which is specified within
 * an attribute called "attribute" and renames the element as specified
 * within an attribute called "element".
 * 
 * Example:<br><br>
 * 
 * <pre>
 * &lt;root xmlns:ev="http://apache.org/cocoon/portal/eventlink/1.0"&gt;
 *   &lt;ev:eventlink href="http://eventlinkexample" element="a" attribute="href"&gt;linktext&lt;/ev:eventlink&gt;
 * &lt;/root&gt;<br></pre>
 *
 * will be replaced with something like:<br><br>
 * 
 * <pre>
 * &lt;root&gt;
 *   &lt;a href="portal?cocoon-portal-event=8"&gt;linktext&lt;/a&gt;
 * &lt;/root&gt;<br></pre>
 * 
 * The transformer will create two CopletLinkEvents and insert corresponding links 
 * to them to the XML instead of "http://eventlinkexample". If such a link is pressed 
 * the corresponding CopletLinkEvent is sent to the Subscribers to be handled.<br>
 * Please see also the documentation of superclass AbstractCopletTransformer for how
 * the coplet instance data are acquired.
 *   
 * @author <a href="mailto:gernot.koller@rizit.at">Gernot Koller</a>
 * 
 * @version CVS $Id: NewEventLinkTransformer.java,v 1.6 2004/03/05 13:02:16 bdelacretaz Exp $
 */
public class NewEventLinkTransformer extends AbstractCopletTransformer {
    /**
     * The namespace URI to listen for.
     */
    public static final String NAMESPACE_URI =
        "http://apache.org/cocoon/portal/eventlink/1.0";

    /**
     * The XML element name to listen for.
     */
    public static final String EVENT_ELEM = "eventlink";

    /**
     * An attribute's name of EVENT_ELEMENT.
     */
    public static final String ATTRIBUTE_ATTR = "attribute";

    /**
     * An attribute's name of EVENT_ELEMENT.
     */
    public static final String ELEMENT_ATTR = "element";

    /**
     * Used to store elements' name between startTransformingElement and endTransformingElement. 
     */
    private Stack elementStack = new Stack();

    /**
     * @see org.apache.avalon.excalibur.pool.Recyclable#recycle()
     */
    public void recycle() {
        super.recycle();
        this.elementStack.clear();
    }

    /**
     * @see java.lang.Object#Object()
     */
    public NewEventLinkTransformer() {
        this.namespaceURI = NAMESPACE_URI;
    }

    /**
     * @throws SAXException when the eventlink element does not contain the necessary attributes
     * 			"element" and "attribute", retrieving the LinkURI from the LinkService fails,
     *          or an unknown element within the namespaces in encountered.
     * @see org.apache.cocoon.transformation.AbstractSAXTransformer#startTransformingElement(String, String, String, Attributes)
     */
    public void startTransformingElement(String uri,
                                         String name,
                                         String raw,
                                         Attributes attributes)
    throws SAXException {
        if (!EVENT_ELEM.equals(name)) {
            throw new SAXException("Unknown element encountered: " + name);
        }

        String attributeName = attributes.getValue(ATTRIBUTE_ATTR);
        String elementName = attributes.getValue(ELEMENT_ATTR);

        if (attributeName == null) {
            throw new SAXException(
                "Element "
                    + EVENT_ELEM
                    + " must have an attribute "
                    + ATTRIBUTE_ATTR
                    + ".");
        }

        if (elementName == null) {
            throw new SAXException(
                "Element "
                    + EVENT_ELEM
                    + " must have an attribute "
                    + ELEMENT_ATTR
                    + ".");
        }

        //remove ATTRIBUTE_ATTR and ELEMENT_ATTR from attributes
        AttributesImpl newAttributes = null;

        if (attributes instanceof AttributesImpl) {
            newAttributes = (AttributesImpl) attributes;
        } else {
            newAttributes = new AttributesImpl(attributes);
        }

        //always iterate backwards when removing elements!
        for (int i = newAttributes.getLength() - 1; i >= 0; i--) {
            if (ELEMENT_ATTR.equals(attributes.getLocalName(i))
                || ATTRIBUTE_ATTR.equals(attributes.getLocalName(i))) {
                newAttributes.removeAttribute(i);
            }
        }

        int index = newAttributes.getIndex(attributeName);
        String link = newAttributes.getValue(index);

        boolean formSpecialTreatment = false;
        if ("form".equals(elementName)) {
            //cut all query parameters from actions with method get, as these will be normaly ignored!
            formSpecialTreatment = true;
            if ("GET".equalsIgnoreCase(newAttributes.getValue("method"))
                && link.indexOf('?') > 0) {
                link = link.substring(0, link.indexOf('?'));
            }
        }

        String portalAction = null;
        String portalEvent = null;

        // if attribute found that contains a link
        if (link != null) {
            CopletInstanceData cid = this.getCopletInstanceData();
            PortalService portalService = null;
            try {
                portalService = (PortalService) this.manager.lookup(PortalService.ROLE);
                // create event link
                CopletLinkEvent event = new CopletLinkEvent(cid, link);
                String eventLink = portalService.getComponentManager().getLinkService().getLinkURI(event);

                //form elements need hidden inputs to change request parameters
                if (formSpecialTreatment) {
                    int begin =
                        eventLink.indexOf("cocoon-portal-action=")
                            + "cocoon-portal-action=".length();
                    int end = eventLink.indexOf('&', begin);
                    if (end == -1) {
                        end = eventLink.length();
                    }

                    portalAction = eventLink.substring(begin, end);

                    begin =
                        eventLink.indexOf("cocoon-portal-event=")
                            + "cocoon-portal-event=".length();
                    end = eventLink.indexOf('&', begin);
                    if (end == -1) {
                        end = eventLink.length();
                    }
                    portalEvent = eventLink.substring(begin, end);

                    eventLink =
                        eventLink.substring(0, eventLink.indexOf('?'));
                }

                // insert event link
                newAttributes.setValue(index, eventLink);
            }
            catch (ServiceException e) {
                throw new SAXException(e);
            } finally {
                this.manager.release(portalService);
            }
        }

        elementStack.push(elementName);

        contentHandler.startElement(
            "",
            elementName,
            elementName,
            newAttributes);

        //generate hidden inputs to add request parameters to the form action
        if (formSpecialTreatment) {
            sendHiddenFields(contentHandler, portalAction, portalEvent);
        }
    }

    /**
     * With forms the uri in the action attribute cannot be enhanced with request parameters.
     * Instead hidden input fields must be inserted into the SAX stream to add request parameters.
     * This method sends two hidden inputs adding the "cocoon-portal-action" parameter and
     * the "cocoon-portal-event" parameter.
     * @param contentHandler the content handler recieving the SAX events
     * @param portalAction value of the "cocoon-portal-action" parameter
     * @param portalEvent value of the "cocoon-portal-event" parameter
     * @throws SAXException if sending the SAX events failed
     */
    private void sendHiddenFields(
        ContentHandler contentHandler,
        String portalAction,
        String portalEvent)
        throws SAXException {
        AttributesImpl attributes = new AttributesImpl();
        attributes.addAttribute("", "type", "type", "CDATA", "hidden");
        attributes.addAttribute(
            "",
            "name",
            "name",
            "CDATA",
            "cocoon-portal-action");
        attributes.addAttribute("", "value", "value", "CDATA", portalAction);
        contentHandler.startElement("", "input", "input", attributes);
        contentHandler.endElement("", "input", "input");

        attributes = new AttributesImpl();
        attributes.addAttribute("", "type", "type", "CDATA", "hidden");
        attributes.addAttribute(
            "",
            "name",
            "name",
            "CDATA",
            "cocoon-portal-event");
        attributes.addAttribute("", "value", "value", "CDATA", portalEvent);
        contentHandler.startElement("", "input", "input", attributes);
        contentHandler.endElement("", "input", "input");
    }

    /**
     * @see org.apache.cocoon.transformation.AbstractSAXTransformer#endTransformingElement(String, String, String)
     */
    public void endTransformingElement(String uri, String name, String raw)
        throws SAXException {
        String elementName = (String) elementStack.pop();
        contentHandler.endElement("", elementName, elementName);
    }
}