Source Code Cross Referenced for RegexpHeaderSelector.java in  » Content-Management-System » apache-lenya-2.0 » org » apache » cocoon » selection » Java Source Code / Java DocumentationJava Source Code and Java Documentation

001:        /*
002:         * Licensed to the Apache Software Foundation (ASF) under one or more
003:         * contributor license agreements.  See the NOTICE file distributed with
004:         * this work for additional information regarding copyright ownership.
005:         * The ASF licenses this file to You under the Apache License, Version 2.0
006:         * (the "License"); you may not use this file except in compliance with
007:         * the License.  You may obtain a copy of the License at
008:         * 
009:         *      http://www.apache.org/licenses/LICENSE-2.0
010:         * 
011:         * Unless required by applicable law or agreed to in writing, software
012:         * distributed under the License is distributed on an "AS IS" BASIS,
013:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014:         * See the License for the specific language governing permissions and
015:         * limitations under the License.
016:         */
017:        package org.apache.cocoon.selection;
018:
019:        import java.util.Map;
020:
021:        import org.apache.avalon.framework.configuration.Configuration;
022:        import org.apache.avalon.framework.configuration.ConfigurationException;
023:        import org.apache.avalon.framework.parameters.Parameters;
024:        import org.apache.cocoon.environment.ObjectModelHelper;
025:
026:        /**
027:         * <p>The {@link RegexpHeaderSelector} class defines a selector matching
028:         * specific headers to configured regular-expression patterns.</p> 
029:         *
030:         * <p>The configuration of an {@link RegexpHeaderSelector} follows exactly
031:         * what has been outlined in {@link AbstractRegexpSelector} regarding regular
032:         * expression patterns, and additionally it requires an extra configuration element
033:         * specifying the header whose value needs to be matched:</p>
034:         * 
035:         * <pre>
036:         * &lt;map:components&gt;
037:         *   ...
038:         *   &lt;map:selectors default="..."&gt;
039:         *     &lt;map:selector name="..." src="org.apache.cocoon.selection...."&gt;
040:         *       &lt;pattern name="empty"&gt;^$&lt;/pattern&gt;
041:         *       &lt;pattern name="number"&gt;^[0-9]+$&lt;/pattern&gt;
042:         *       &lt;pattern name="string"&gt;^.+$&lt;/pattern&gt;
043:         *       &lt;header-name&gt;...&lt;/header-name&gt;
044:         *     &lt;/map:selector&gt;
045:         *  &lt;/map:selectors&gt;
046:         * &lt;/map:components&gt;
047:         * </pre>
048:         * 
049:         * <p>If not configured, or if it needs to be overriddent, the header name can
050:         * also be specified as a <code>&lt;map:parameter&nbsp;.../&gt;</code> inside the
051:         * pipeline itself.</p>
052:         * 
053:         * @version CVS $Id: RegexpHeaderSelector.java 433543 2006-08-22 06:22:54Z crossley $
054:         */
055:        public class RegexpHeaderSelector extends AbstractRegexpSelector {
056:
057:            /** <p>The name of the header to work on.</p> */
058:            protected String headerName;
059:
060:            /**
061:             * <p>Create a new {@link RegexpHeaderSelector} instance.</p>
062:             */
063:            public RegexpHeaderSelector() {
064:                super ();
065:            }
066:
067:            /**
068:             * <p>Configure this instance parsing all regular expression patterns and
069:             * storing the header name upon which selection occurs.</p>
070:             * 
071:             * @param configuration the {@link Configuration} instance where configured
072:             *                      patterns are defined.
073:             * @throws ConfigurationException if one of the regular-expression to configure
074:             *                                could not be compiled.
075:             */
076:            public void configure(Configuration configuration)
077:                    throws ConfigurationException {
078:                super .configure(configuration);
079:                this .headerName = configuration.getChild("header-name")
080:                        .getValue(null);
081:            }
082:
083:            /**
084:             * <p>Return the value of the header identified by the configured header
085:             * name, if any.</p>
086:             * 
087:             * @param objectModel the Cocoon object model.
088:             * @param parameters the {@link Parameters} associated with the pipeline.
089:             * @return the value of the configured request parameter or <b>null</b>.
090:             */
091:            public Object getSelectorContext(Map objectModel,
092:                    Parameters parameters) {
093:                String name = parameters.getParameter("header-name",
094:                        this .headerName);
095:                if (name == null) {
096:                    this .getLogger().warn("No header name given -- failing.");
097:                    return null;
098:                }
099:                return ObjectModelHelper.getRequest(objectModel)
100:                        .getHeader(name);
101:            }
102:
103:            /**
104:             * Selectors test pattern against some objects in a <code>Map</code>
105:             * model and signals success with the returned boolean value
106:             * @param expr        The expression to test.
107:             * @return Signals successful test.
108:             */
109:            public boolean select(String expr, Map objectModel,
110:                    Parameters params) {
111:                // Inform proxies that response varies with the selector header
112:                String name = params.getParameter("header-name",
113:                        this .headerName);
114:                if (name != null)
115:                    ObjectModelHelper.getResponse(objectModel).addHeader(
116:                            "Vary", name);
117:                return select(expr, getSelectorContext(objectModel, params));
118:            }
119:
120:        }