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.language.simple;
018
019 import java.util.ArrayList;
020 import java.util.List;
021
022 import org.apache.camel.Exchange;
023 import org.apache.camel.Expression;
024 import org.apache.camel.Predicate;
025 import org.apache.camel.builder.ExpressionBuilder;
026 import org.apache.camel.builder.PredicateBuilder;
027 import org.apache.camel.language.IllegalSyntaxException;
028 import org.apache.camel.spi.Language;
029 import org.apache.camel.util.ObjectHelper;
030
031 /**
032 * A <a href="http://activemq.apache.org/camel/simple.html">simple language</a>
033 * which maps simple property style notations to access headers and bodies.
034 * Examples of supported expressions are <p/>
035 * <ul>
036 * <li>in.header.foo or header.foo to access an inbound header called 'foo'</li>
037 * <li>in.body or body to access the inbound body</li>
038 * <li>out.header.foo to access an outbound header called 'foo'</li>
039 * <li>out.body to access the inbound body</li>
040 * <li>property.foo to access the exchange property called 'foo'</li>
041 * <li>sys.foo to access the system property called 'foo'</li>
042 * </ul>
043 *
044 * @version $Revision: 659197 $
045 */
046 public class SimpleLanguage implements Language {
047
048 public static Expression simple(String expression) {
049 SimpleLanguage language = new SimpleLanguage();
050 return language.createExpression(expression);
051 }
052
053 public Predicate<Exchange> createPredicate(String expression) {
054 return PredicateBuilder.toPredicate(createExpression(expression));
055 }
056
057 public Expression<Exchange> createExpression(String expression) {
058 if (expression.indexOf("${") >= 0) {
059 return createComplexExpression(expression);
060 }
061 return createSimpleExpression(expression);
062 }
063
064 protected Expression<Exchange> createComplexExpression(String expression) {
065 List<Expression> results = new ArrayList<Expression>();
066
067 int pivot = 0;
068 int size = expression.length();
069 while (pivot < size) {
070 int idx = expression.indexOf("${", pivot);
071 if (idx < 0) {
072 results.add(createConstantExpression(expression, pivot, size));
073 break;
074 } else {
075 if (pivot < idx) {
076 results.add(createConstantExpression(expression, pivot, idx));
077 }
078 pivot = idx + 2;
079 int endIdx = expression.indexOf("}", pivot);
080 if (endIdx < 0) {
081 throw new IllegalArgumentException("Expecting } but found end of string for simple expression: " + expression);
082 }
083 String simpleText = expression.substring(pivot, endIdx);
084
085 Expression simpleExpression = createSimpleExpression(simpleText);
086 results.add(simpleExpression);
087 pivot = endIdx + 1;
088 }
089 }
090 return ExpressionBuilder.concatExpression(results, expression);
091 }
092
093 protected Expression createConstantExpression(String expression, int start, int end) {
094 return ExpressionBuilder.constantExpression(expression.substring(start, end));
095 }
096
097 protected Expression<Exchange> createSimpleExpression(String expression) {
098 if (ObjectHelper.isEqualToAny(expression, "body", "in.body")) {
099 return ExpressionBuilder.bodyExpression();
100 } else if (ObjectHelper.equal(expression, "out.body")) {
101 return ExpressionBuilder.outBodyExpression();
102 }
103
104 // in header expression
105 String remainder = ifStartsWithReturnRemainder("in.header.", expression);
106 if (remainder == null) {
107 remainder = ifStartsWithReturnRemainder("header.", expression);
108 }
109 if (remainder == null) {
110 remainder = ifStartsWithReturnRemainder("headers.", expression);
111 }
112 if (remainder == null) {
113 remainder = ifStartsWithReturnRemainder("in.headers.", expression);
114 }
115 if (remainder != null) {
116 return ExpressionBuilder.headerExpression(remainder);
117 }
118
119 // out header expression
120 remainder = ifStartsWithReturnRemainder("out.header.", expression);
121 if (remainder == null) {
122 remainder = ifStartsWithReturnRemainder("out.headers.", expression);
123 }
124 if (remainder != null) {
125 return ExpressionBuilder.outHeaderExpression(remainder);
126 }
127
128 // property
129 remainder = ifStartsWithReturnRemainder("property.", expression);
130 if (remainder != null) {
131 return ExpressionBuilder.propertyExpression(remainder);
132 }
133
134 // system property
135 remainder = ifStartsWithReturnRemainder("sys.", expression);
136 if (remainder != null) {
137 return ExpressionBuilder.propertyExpression(remainder);
138 }
139 throw new IllegalSyntaxException(this, expression);
140 }
141
142 protected String ifStartsWithReturnRemainder(String prefix, String text) {
143 if (text.startsWith(prefix)) {
144 String remainder = text.substring(prefix.length());
145 if (remainder.length() > 0) {
146 return remainder;
147 }
148 }
149 return null;
150 }
151 }