/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.camel.language.spel;
import org.apache.camel.Exchange;
import org.apache.camel.ExpressionEvaluationException;
import org.apache.camel.impl.ExpressionSupport;
import org.apache.camel.spring.SpringCamelContext;
import org.springframework.context.ApplicationContext;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ParserContext;
import org.springframework.expression.common.TemplateParserContext;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
/**
* Class responsible for evaluating <a href="http://static.springsource.org
* /spring/docs/current/spring-framework-reference/html/expressions.html">
* Spring Expression Language</a> in the context of Camel.
*/
public class SpelExpression extends ExpressionSupport {
private final String expressionString;
private final Class<?> type;
// SpelExpressionParser is thread-safe according to the docs
private final SpelExpressionParser expressionParser;
public SpelExpression(String expressionString, Class<?> type) {
this.expressionString = expressionString;
this.type = type;
this.expressionParser = new SpelExpressionParser();
}
public static SpelExpression spel(String expression) {
return new SpelExpression(expression, Object.class);
}
public <T> T evaluate(Exchange exchange, Class<T> tClass) {
try {
Expression expression = parseExpression();
EvaluationContext evaluationContext = createEvaluationContext(exchange);
Object value = expression.getValue(evaluationContext);
// Let Camel handle the type conversion
return exchange.getContext().getTypeConverter().convertTo(tClass, value);
} catch (Exception e) {
throw new ExpressionEvaluationException(this, exchange, e);
}
}
private EvaluationContext createEvaluationContext(Exchange exchange) {
StandardEvaluationContext evaluationContext = new StandardEvaluationContext(new RootObject(exchange));
if (exchange.getContext() instanceof SpringCamelContext) {
// Support references (like @foo) in expressions to beans defined in the Registry/ApplicationContext
ApplicationContext applicationContext = ((SpringCamelContext) exchange.getContext()).getApplicationContext();
evaluationContext.setBeanResolver(new BeanFactoryResolver(applicationContext));
}
return evaluationContext;
}
private Expression parseExpression() {
// Support template parsing with #{ } delimiters
ParserContext parserContext = new TemplateParserContext();
Expression expression = expressionParser.parseExpression(expressionString, parserContext);
return expression;
}
public Class<?> getType() {
return type;
}
protected String assertionFailureMessage(Exchange exchange) {
return expressionString;
}
@Override
public String toString() {
return "SpelExpression[" + expressionString + "]";
}
}