/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.selection;
import java.util.Map;
import org.apache.avalon.framework.activity.Disposable;
import org.apache.avalon.framework.logger.AbstractLogEnabled;
import org.apache.avalon.framework.parameters.Parameters;
import org.apache.avalon.framework.service.ServiceException;
import org.apache.avalon.framework.service.ServiceManager;
import org.apache.avalon.framework.service.Serviceable;
import org.apache.avalon.framework.thread.ThreadSafe;
import org.apache.excalibur.source.Source;
import org.apache.excalibur.source.SourceNotFoundException;
import org.apache.excalibur.source.SourceResolver;
/**
* Selects the first of a set of Resources (usually files) that exists.
*
* <p>
* A parameter 'prefix',
* <pre>
* <map:parameter src="prefix" value="<code>some/path</code>"/<
* </pre>
* may be supplied to the selector instance. This prefix is prepended to all
* test expressions before evaluation. The default prefix is '' (empty string),
* meaning that all expressions are relative to the current sitemap, unless
* explicitly overridden.
*
* <p><b>NOTE:</b>
* Provided resource URI is resolved as Source, relative to the current
* sitemap, which differs from behavior of selector in previous versions.
* To resolve resource paths relative to the context root, provide prefix
* parameter:
* <pre>
* <map:parameter name="prefix" value="context://"/<
* </pre>
*
* <p>
* For example, we could define a ResourceExistsSelector with:
* <pre>
* <map:selector name="resource-exists"
* logger="sitemap.selector.resource-exists"
* src="org.apache.cocoon.selection.ResourceExistsSelector" /<
* </pre>
* And use it to build a PDF from XSL:FO or a higher-level XML format with:
*
* <pre>
* <map:match pattern="**.pdf"<
* <map:select type="resource-exists"<
* <map:when test="context/xdocs/{1}.fo"<
* <map:generate src="content/xdocs/{1}.fo" /<
* </map:when<
* <map:otherwise<
* <map:generate src="content/xdocs/{1}.xml" /<
* <map:transform src="stylesheets/document2fo.xsl" /<
* </map:otherwise<
* </map:select<
* <map:serialize type="fo2pdf" /<
* </pre>
*
* @author <a href="mailto:jefft@apache.org">Jeff Turner</a>
* @author <a href="mailto:vgritsenko@apache.org">Vadim Gritsenko</a>
* @version CVS $Id$
*/
public class ResourceExistsSelector extends AbstractLogEnabled
implements ThreadSafe, Serviceable, Disposable, Selector {
private ServiceManager manager;
private SourceResolver resolver;
public void service(ServiceManager manager) throws ServiceException {
this.manager = manager;
this.resolver = (SourceResolver)manager.lookup(SourceResolver.ROLE);
}
public void dispose() {
this.manager.release(this.resolver);
this.resolver = null;
this.manager = null;
}
public boolean select(String expression, Map objectModel, Parameters parameters) {
String resourceURI = parameters.getParameter("prefix", "") + expression;
Source source = null;
try {
source = resolver.resolveURI(resourceURI);
return source.exists();
} catch (SourceNotFoundException e) {
return false;
} catch (Exception e) {
getLogger().warn("Exception resolving resource " + resourceURI, e);
return false;
} finally {
if (source != null) {
resolver.release(source);
}
}
}
}