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.spel;
018
019 import org.apache.camel.Exchange;
020 import org.apache.camel.ExpressionEvaluationException;
021 import org.apache.camel.impl.ExpressionSupport;
022 import org.apache.camel.spring.SpringCamelContext;
023 import org.springframework.context.ApplicationContext;
024 import org.springframework.context.expression.BeanFactoryResolver;
025 import org.springframework.expression.EvaluationContext;
026 import org.springframework.expression.Expression;
027 import org.springframework.expression.ParserContext;
028 import org.springframework.expression.common.TemplateParserContext;
029 import org.springframework.expression.spel.standard.SpelExpressionParser;
030 import org.springframework.expression.spel.support.StandardEvaluationContext;
031
032 /**
033 * Class responsible for evaluating <a href="http://static.springsource.org
034 * /spring/docs/current/spring-framework-reference/html/expressions.html">
035 * Spring Expression Language</a> in the context of Camel.
036 */
037 public class SpelExpression extends ExpressionSupport {
038
039 private final String expressionString;
040 private final Class<?> type;
041
042 // SpelExpressionParser is thread-safe according to the docs
043 private final SpelExpressionParser expressionParser;
044
045 public SpelExpression(String expressionString, Class<?> type) {
046 this.expressionString = expressionString;
047 this.type = type;
048 this.expressionParser = new SpelExpressionParser();
049 }
050
051 public static SpelExpression spel(String expression) {
052 return new SpelExpression(expression, Object.class);
053 }
054
055 public <T> T evaluate(Exchange exchange, Class<T> tClass) {
056 try {
057 Expression expression = parseExpression();
058 EvaluationContext evaluationContext = createEvaluationContext(exchange);
059 Object value = expression.getValue(evaluationContext);
060 // Let Camel handle the type conversion
061 return exchange.getContext().getTypeConverter().convertTo(tClass, value);
062 } catch (Exception e) {
063 throw new ExpressionEvaluationException(this, exchange, e);
064 }
065 }
066
067 private EvaluationContext createEvaluationContext(Exchange exchange) {
068 StandardEvaluationContext evaluationContext = new StandardEvaluationContext(new RootObject(exchange));
069 if (exchange.getContext() instanceof SpringCamelContext) {
070 // Support references (like @foo) in expressions to beans defined in the Registry/ApplicationContext
071 ApplicationContext applicationContext = ((SpringCamelContext) exchange.getContext()).getApplicationContext();
072 evaluationContext.setBeanResolver(new BeanFactoryResolver(applicationContext));
073 }
074 return evaluationContext;
075 }
076
077 private Expression parseExpression() {
078 // Support template parsing with #{ } delimiters
079 ParserContext parserContext = new TemplateParserContext();
080 Expression expression = expressionParser.parseExpression(expressionString, parserContext);
081 return expression;
082 }
083
084 public Class<?> getType() {
085 return type;
086 }
087
088 protected String assertionFailureMessage(Exchange exchange) {
089 return expressionString;
090 }
091
092 @Override
093 public String toString() {
094 return "SpelExpression[" + expressionString + "]";
095 }
096 }