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.camel;
018
019 /**
020 * @version $Revision: $
021 */
022 public class Expressions {
023
024 /**
025 * Returns an expression for the header value with the given name
026 *
027 * @param headerName the name of the header the expression will return
028 * @return an expression object which will return the header value
029 */
030 public static <E extends Exchange> Expression<E> headerExpression(final String headerName) {
031 return new Expression<E>() {
032 public Object evaluate(E exchange) {
033 Object header = exchange.getIn().getHeaders().getHeader(headerName);
034 if (header == null) {
035 // lets try the exchange header
036 header = exchange.getHeaders().getHeader(headerName);
037 }
038 return header;
039 }
040
041 @Override
042 public String toString() {
043 return "header(" + headerName + ")";
044 }
045 };
046 }
047 /**
048 * Returns an expression for the contant value
049 *
050 * @param value the value the expression will return
051 * @return an expression object which will return the constant value
052 */
053 public static <E extends Exchange> Expression<E> constantExpression(final Object value) {
054 return new Expression<E>() {
055 public Object evaluate(E exchange) {
056 return value;
057 }
058
059 @Override
060 public String toString() {
061 return "" + value;
062 }
063 };
064 }
065 }