[newbie] UrlExistsSelector

[Martin Kal�n]

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: [EMAIL PROTECTED]
SE-182 79  Stocksund    Tel:  +46-8-410 064 40
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.
 * 
 * Like [EMAIL PROTECTED] org.apache.cocoon.selection.ResourceExistsSelector},
 * but works with java.net.URL instead of using the servlet
 * containter's context resolving.
 *
 * @author Martin Kalén
 * @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 = "" 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;
        }
    }

}