001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
003// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
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// *                                                                                                                         *
009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an  *
010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.rest.vars;
014
015import org.apache.juneau.http.response.*;
016import org.apache.juneau.rest.*;
017import org.apache.juneau.svl.*;
018
019/**
020 * Request header variable resolver.
021 *
022 * <p>
023 * The format for this var is <js>"$RH{key1[,key2...]}"</js>.
024 *
025 * <p>
026 * Used to resolve values returned by {@link RestRequest#getHeader(String)}.
027 * <br>When multiple keys are used, returns the first non-null/empty value.
028 *
029 * <h5 class='section'>Example:</h5>
030 * <p class='bjava'>
031 *    String <jv>foo</jv> = <jv>restRequest</jv>.getVarResolver().resolve(<js>"$RH{foo}"</js>);
032 *    String <jv>fooOrBar</jv> = <jv>restRequest</jv>.getVarResolver().resolve(<js>"$RH{foo,bar}"</js>);
033 * </p>
034 *
035 * <h5 class='section'>Notes:</h5><ul>
036 *    <li class='note'>
037 *       This variable resolver requires that a {@link RestRequest} bean be available in the session bean store.
038 *    <li class='note'>
039 *       For security reasons, nested and recursive variables are not resolved.
040 * </ul>
041 *
042 * <h5 class='section'>See Also:</h5><ul>
043 *    <li class='link'><a class="doclink" href="../../../../../index.html#jm.SvlVariables">SVL Variables</a>
044 * </ul>
045 */
046public class RequestHeaderVar extends MultipartResolvingVar {
047
048   /** The name of this variable. */
049   public static final String NAME = "RH";
050
051   /**
052    * Constructor.
053    */
054   public RequestHeaderVar() {
055      super(NAME);
056   }
057
058   @Override /* Var */
059   protected boolean allowNested() {
060      return false;
061   }
062
063   @Override /* Var */
064   protected boolean allowRecurse() {
065      return false;
066   }
067
068   @Override /* Var */
069   public String resolve(VarResolverSession session, String key) {
070      return session.getBean(RestRequest.class).orElseThrow(InternalServerError::new).getHeaderParam(key).orElse(null);
071   }
072
073   @Override /* Var */
074   public boolean canResolve(VarResolverSession session) {
075      return session.getBean(RestRequest.class).isPresent();
076   }
077}