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Camel REST (Restlet baesd) Component
There is a newer version: 3.0.0-RC2
/**
 * 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.component.restlet;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.camel.CamelExchangeException;
import org.apache.camel.Exchange;
import org.apache.camel.impl.DefaultProducer;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.restlet.Client;
import org.restlet.Context;
import org.restlet.data.Request;
import org.restlet.data.Response;

/**
 * A Camel producer that acts as a client to Restlet server.
 *
 * @version $Revision: 989557 $
 */
public class RestletProducer extends DefaultProducer {
    private static final Log LOG = LogFactory.getLog(RestletProducer.class);
    private static final Pattern PATTERN = Pattern.compile("\\{([\\w\\.]*)\\}");
    private Client client;

    public RestletProducer(RestletEndpoint endpoint) throws Exception {
        super(endpoint);
        client = new Client(endpoint.getProtocol());
        client.setContext(new Context());
    }

    @Override
    public void doStart() throws Exception {
        super.doStart();
        client.start();
    }
    
    @Override
    public void doStop() throws Exception {
        client.stop();
        super.doStop();
    }
    
    public void process(Exchange exchange) throws Exception {
        RestletEndpoint endpoint = (RestletEndpoint)getEndpoint();
        
        String resourceUri = buildUri(endpoint, exchange);
        Request request = new Request(endpoint.getRestletMethod(), resourceUri);

        RestletBinding binding = endpoint.getRestletBinding();
        binding.populateRestletRequestFromExchange(request, exchange);
        
        if (LOG.isDebugEnabled()) {
            LOG.debug("Client sends a request (method: " + request.getMethod() 
                    + ", uri: " + resourceUri + ")");
        }
        
        Response response = client.handle(request);
        binding.populateExchangeFromRestletResponse(exchange, response);
    }

    private static String buildUri(RestletEndpoint endpoint, Exchange exchange) throws CamelExchangeException {
        String uri = endpoint.getProtocol() + "://" + endpoint.getHost() + ":" 
            + endpoint.getPort() + endpoint.getUriPattern();

        // substitute { } placeholders in uri and use mandatory headers
        if (LOG.isTraceEnabled()) {
            LOG.trace("Substituting { } placeholders in uri: " + uri);
        }
        Matcher matcher = PATTERN.matcher(uri);
        while (matcher.find()) {
            String key = matcher.group(1);
            String header = exchange.getIn().getHeader(key, String.class);
            // header should be mandatory
            if (header == null) {
                throw new CamelExchangeException("Header with key: " + key + " not found in Exchange", exchange);
            }

            if (LOG.isTraceEnabled()) {
                LOG.trace("Replacing: " + matcher.group(0) + " with header value: " + header);
            }

            uri = matcher.replaceFirst(header);
            // we replaced uri so reset and go again
            matcher.reset(uri);
        }

        if (LOG.isDebugEnabled()) {
            LOG.debug("Using uri: " + uri);
        }

        return uri;
    }

}