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 }