messageheaderexpressionevaluator.java

提供ESB 应用mule源代码 提供ESB 应用mule源代码

/*
 * $Id: MessageHeaderExpressionEvaluator.java 13054 2008-10-10 21:45:36Z dfeist $
 * --------------------------------------------------------------------------------------
 * Copyright (c) MuleSource, Inc.  All rights reserved.  http://www.mulesource.com
 *
 * The software in this package is published under the terms of the CPAL v1.0
 * license, a copy of which has been included with this distribution in the
 * LICENSE.txt file.
 */

package org.mule.util.expression;

import org.mule.RequestContext;
import org.mule.api.transport.MessageAdapter;

/**
 * Looks up the property on the message using the property name given.  If the call on the messgae returns null,
 * parameters on the inbound endpoint will also be checked.
 *
 * @see MessageHeadersListExpressionEvaluator
 * @see MessageHeadersExpressionEvaluator
 * @see ExpressionEvaluator
 * @see ExpressionEvaluatorManager
 */
public class MessageHeaderExpressionEvaluator implements ExpressionEvaluator
{
    public static final String NAME = "header";

    public Object evaluate(String expression, Object message)
    {
        Object result = null;
        if (message instanceof MessageAdapter)
        {
            result = ((MessageAdapter) message).getProperty(expression);
            //Should this fallback be in its own expression evaluator i.e. #[endpoint-param:foo] ??
            //I'm not sure becaus ethis way there is a fallback where the message doesn't have a value the
            //endpoint can define a default
            if (result == null && RequestContext.getEventContext() != null)
            {
                result = RequestContext.getEventContext().getEndpointURI().getParams().get(expression);
            }
        }
        return result;
    }

    /**
     * {@inheritDoc}
     */
    public String getName()
    {
        return NAME;
    }

    /**
     * {@inheritDoc}
     */
    public void setName(String name)
    {
        throw new UnsupportedOperationException("setName");
    }
}