001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
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004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
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011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.rest.vars;
014
015import org.apache.juneau.rest.*;
016import org.apache.juneau.svl.*;
017
018/**
019 * Request header variable resolver.
020 * 
021 * <p>
022 * The format for this var is <js>"$RH{key1[,key2...]}"</js>.
023 * 
024 * <p>
025 * Used to resolve values returned by {@link RestRequest#getHeader(String)}.
026 * <br>When multiple keys are used, returns the first non-null/empty value.
027 * 
028 * <h5 class='section'>Example:</h5>
029 * <p class='bcode'>
030 *    String foo = restRequest.resolveVars(<js>"$RH{Foo}"</js>); 
031 *    String fooOrBar = restRequest.resolveVars(<js>"$RH{Foo,Bar}"</js>); 
032 * </p>
033 * 
034 * <h5 class='section'>Notes:</h5>
035 * <ul class='spaced-list'>
036 *    <li>
037 *       This variable resolver requires that a {@link RestRequest} object be set as a context object on the resolver 
038 *       or a session object on the resolver session.
039 *    <li>
040 *       For security reasons, nested and recursive variables are not resolved.
041 * </ul>
042 * 
043 * <h5 class='section'>See Also:</h5>
044 * <ul>
045 *    <li class='link'><a class="doclink" href="../../../../../overview-summary.html#juneau-rest-server.SvlVariables">Overview &gt; juneau-rest-server &gt; SVL Variables</a>
046 * </ul>
047 */
048public class RequestHeaderVar extends MultipartResolvingVar {
049
050   /**
051    * The name of the session or context object that identifies the {@link RestRequest} object.
052    */
053   public static final String SESSION_req = "req";
054
055
056   /** The name of this variable. */
057   public static final String NAME = "RH";
058
059   /**
060    * Constructor.
061    */
062   public RequestHeaderVar() {
063      super(NAME);
064   }
065   
066   @Override /* Var */
067   protected boolean allowNested() {
068      return false;
069   }
070
071   @Override /* Var */
072   protected boolean allowRecurse() {
073      return false;
074   }
075
076   @Override /* Parameter */
077   public String resolve(VarResolverSession session, String key) {
078      RestRequest req = session.getSessionObject(RestRequest.class, SESSION_req);
079      return req.getHeader(key);
080   }
081}