/*
* 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.configuration.Configuration;
import org.apache.avalon.framework.configuration.ConfigurationException;
import org.apache.avalon.framework.parameters.Parameters;
import org.apache.cocoon.environment.ObjectModelHelper;
/**
* <p>The {@link RegexpHeaderSelector} class defines a selector matching
* specific headers to configured regular-expression patterns.</p>
*
* <p>The configuration of an {@link RegexpHeaderSelector} follows exactly
* what has been outlined in {@link AbstractRegexpSelector} regarding regular
* expression patterns, and additionally it requires an extra configuration element
* specifying the header whose value needs to be matched:</p>
*
* <pre>
* <map:components>
* ...
* <map:selectors default="...">
* <map:selector name="..." src="org.apache.cocoon.selection....">
* <pattern name="empty">^$</pattern>
* <pattern name="number">^[0-9]+$</pattern>
* <pattern name="string">^.+$</pattern>
* <header-name>...</header-name>
* </map:selector>
* </map:selectors>
* </map:components>
* </pre>
*
* <p>If not configured, or if it needs to be overriddent, the header name can
* also be specified as a <code><map:parameter .../></code> inside the
* pipeline itself.</p>
*
* @version CVS $Id$
*/
public class RegexpHeaderSelector extends AbstractRegexpSelector {
/** <p>The name of the header to work on.</p> */
protected String headerName;
/**
* <p>Create a new {@link RegexpHeaderSelector} instance.</p>
*/
public RegexpHeaderSelector() {
super();
}
/**
* <p>Configure this instance parsing all regular expression patterns and
* storing the header name upon which selection occurs.</p>
*
* @param configuration the {@link Configuration} instance where configured
* patterns are defined.
* @throws ConfigurationException if one of the regular-expression to configure
* could not be compiled.
*/
public void configure(Configuration configuration)
throws ConfigurationException {
super.configure(configuration);
this.headerName = configuration.getChild("header-name").getValue(null);
}
/**
* <p>Return the value of the header identified by the configured header
* name, if any.</p>
*
* @param objectModel the Cocoon object model.
* @param parameters the {@link Parameters} associated with the pipeline.
* @return the value of the configured request parameter or <b>null</b>.
*/
public Object getSelectorContext(Map objectModel, Parameters parameters) {
String name = parameters.getParameter("header-name", this.headerName);
if (name == null) {
this.getLogger().warn("No header name given -- failing.");
return null;
}
return ObjectModelHelper.getRequest(objectModel).getHeader(name);
}
/**
* Selectors test pattern against some objects in a <code>Map</code>
* model and signals success with the returned boolean value
* @param expr The expression to test.
* @return Signals successful test.
*/
public boolean select(String expr, Map objectModel, Parameters params) {
// Inform proxies that response varies with the selector header
String name = params.getParameter("header-name", this.headerName);
if (name != null)
ObjectModelHelper.getResponse(objectModel).addHeader("Vary", name);
return select(expr, getSelectorContext(objectModel, params));
}
}