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 */
017package org.apache.camel.language.spel;
018
019import org.apache.camel.Exchange;
020import org.apache.camel.ExpressionEvaluationException;
021import org.apache.camel.impl.ExpressionSupport;
022import org.apache.camel.spring.SpringCamelContext;
023import org.springframework.context.ApplicationContext;
024import org.springframework.context.expression.BeanFactoryResolver;
025import org.springframework.expression.EvaluationContext;
026import org.springframework.expression.Expression;
027import org.springframework.expression.ParserContext;
028import org.springframework.expression.common.TemplateParserContext;
029import org.springframework.expression.spel.standard.SpelExpressionParser;
030import 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@SuppressWarnings("deprecation")
038public class SpelExpression extends ExpressionSupport {
039
040    private final String expressionString;
041    private final Class<?> type;
042
043    // SpelExpressionParser is thread-safe according to the docs
044    private final SpelExpressionParser expressionParser;
045
046    public SpelExpression(String expressionString, Class<?> type) {
047        this.expressionString = expressionString;
048        this.type = type;
049        this.expressionParser = new SpelExpressionParser();
050    }
051
052    public static SpelExpression spel(String expression) {
053        return new SpelExpression(expression, Object.class);
054    }
055
056    public <T> T evaluate(Exchange exchange, Class<T> tClass) {
057        try {
058            Expression expression = parseExpression();
059            EvaluationContext evaluationContext = createEvaluationContext(exchange);
060            Object value = expression.getValue(evaluationContext);
061            // Let Camel handle the type conversion
062            return exchange.getContext().getTypeConverter().convertTo(tClass, value);
063        } catch (Exception e) {
064            throw new ExpressionEvaluationException(this, exchange, e);
065        }
066    }
067
068    private EvaluationContext createEvaluationContext(Exchange exchange) {
069        StandardEvaluationContext evaluationContext = new StandardEvaluationContext(new RootObject(exchange));
070        if (exchange.getContext() instanceof SpringCamelContext) {
071            // Support references (like @foo) in expressions to beans defined in the Registry/ApplicationContext
072            ApplicationContext applicationContext = ((SpringCamelContext) exchange.getContext()).getApplicationContext();
073            evaluationContext.setBeanResolver(new BeanFactoryResolver(applicationContext));
074        }
075        return evaluationContext;
076    }
077
078    private Expression parseExpression() {
079        // Support template parsing with #{ } delimiters
080        ParserContext parserContext = new TemplateParserContext();
081        Expression expression = expressionParser.parseExpression(expressionString, parserContext);
082        return expression;
083    }
084
085    public Class<?> getType() {
086        return type;
087    }
088
089    protected String assertionFailureMessage(Exchange exchange) {
090        return expressionString;
091    }
092
093    @Override
094    public String toString() {
095        return "SpelExpression[" + expressionString + "]";
096    }
097}