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Message-ID: <3F86849A.90707@curalia.se>
Date: Fri, 10 Oct 2003 12:06:18 +0200
From: =?ISO-8859-1?Q?Martin_Kal=E9n?= <martin.kalen@curalia.se>
Organization: Curalia AB
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To: dev@cocoon.apache.org
Subject: [newbie] UrlExistsSelector
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Greetings developers,

  as a newbie to the wonderful world of Cocoon sitemaps I was struggling 
with the problem of using a selector to determine if an external HTTP 
URL was available.


* Problem description:

A pipeline matcher with the following steps is triggered:
1. XSP generation
2. cinclude transformation
3. XSLT transformation
4. HTML serialization

The cinclude in step 2 triggers another cocoon pipeline. XSP snippet:
<ci:include src="cocoon:/(name of pipeline #2)" 
xmlns:ci="http://apache.org/cocoon/include/1.0"/>

Pipeline #2:
1. (what I wanted) map:select and generation based on status of external 
HTTP URL
2. XSLT transformation
3. XML serialization


* My soloution:

I was first trying the map:select with the 
org.apache.cocoon.selection.ResourceExistsSelector until I found out 
that this was only for content within the current servlet context.

I then wrote the attached (trivial) UrlExistsSelector and used this one 
for step 1 in pipeline #2.

This works, but might have som implications in security/performance (no 
timeout handling) etc. etc. that I just don't see because I'm new to Cocoon.


Any comments? Other soloutions?
TIA,
  Martin

-- 
Martin Kal�n
Curalia AB              Web:  http://www.curalia.se
Orrspelsv�gen 2B        Mail: info@curalia.se
SE-182 79  Stocksund    Tel:  +46-8-410 064 40

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import org.apache.avalon.framework.logger.AbstractLogEnabled;
import org.apache.avalon.framework.parameters.Parameters;
import org.apache.avalon.framework.thread.ThreadSafe;
import org.apache.cocoon.selection.Selector;

import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Map;

/**
 * Selects the first of a set of URLs that can be connected to.
 * <p>
 * Like {@link org.apache.cocoon.selection.ResourceExistsSelector},
 * but works with <code>java.net.URL</code> instead of using the servlet
 * containter's context resolving.
 *
 * @author <a href="mailto:martin.kalen@curalia.se">Martin Kal&eacute;n</a>
 * @version CVS $Id: UrlExistsSelector.java,v 1.1 2003/10/10 09:08:47 martin Exp $
 */
public class UrlExistsSelector extends AbstractLogEnabled
    implements ThreadSafe, Selector {

    public boolean select(String expression,
			  Map objectModel,
			  Parameters parameters) {
        try {
            URL url = new URL(expression);
            URLConnection connection = url.openConnection();
            connection.connect();
            return true;
        } catch (MalformedURLException e) {
            StringBuffer message = new StringBuffer();
            message.append("Selector expression '");
            message.append(expression);
            message.append("' is not a valid URL");
            getLogger().warn(message.toString());
            return false;
        } catch (Exception e) {
            return false;
        }
    }

}

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