Camel Spring MVC集成

Question

I want to expose RESTful service using Spring MVC and Camel integration server. This service will accept JSON as an input and return JSON output only.

Main Idea - define a route which accepts POST request from some URI, the Camel forwards this request to Spring controller, Spring controller return some JSON response and Camel should process it and return to the rest client.

Here the route I am defining

<camel:route>
    <camel:from
            uri="restlet:/url1?restletMethod=POST" />
        <camel:setBody>
                <camel:simple>${body}</camel:simple>
        </camel:setBody>
        <camel:setHeader headerName="Content-Type">
            <camel:constant>{application/json}</camel:constant>
        </camel:setHeader>
            <camel:to uri="restlet:{springMVCUrl}?restletMethod=POST" />
</camel:route>

I hit Url1 from firefox Rest client and send my JSON, request comes from Camel to my Spring controller and it return the JSON string. If I debug the code in eclipse on camel side, it works absolutely fine.

But if I run without debug mode it always return null body

Is it some synch issue, or inout channel?

Answer 1

The issue you are facing is that of Async processing behaviour of Restlet producer endpoint. For detailed information on Camel Asynchronous processing and how different components use that is detailed here . The "from" part invokes a RestletConsumer and the "to" part of the route invokes a RestletProducer . Restlet producer by default runs in Async mode where it is just passed the exchange and on completing the work (in your case call to external srvice) it populates the exchange. This can be verified in the RestletProducer class which implements DefaultAsyncProducer

public class RestletProducer extends DefaultAsyncProducer {

.......................................
......................................

 @Override
    public boolean process(final Exchange exchange, final AsyncCallback callback) {
        RestletEndpoint endpoint = (RestletEndpoint) getEndpoint();

        final RestletBinding binding = endpoint.getRestletBinding();
        Request request;
        try {
            String resourceUri = buildUri(endpoint, exchange);
            request = new Request(endpoint.getRestletMethod(), resourceUri);
            binding.populateRestletRequestFromExchange(request, exchange);
        } catch (CamelExchangeException e) {
            // break out in case of exception
            exchange.setException(e);
            callback.done(true);
            return true;
        }

        // process the request asynchronously
        LOG.debug("Sending request: {} for exchangeId: {}", request, exchange.getExchangeId());
        client.handle(request, new Uniform() {
            @Override
            public void handle(Request request, Response response) {
                LOG.debug("Received response: {} for exchangeId: {}", response, exchange.getExchangeId());
                try {
                    if (response != null) {
                        Integer respCode = response.getStatus().getCode();
                        if (respCode > 207 && throwException) {
                            exchange.setException(populateRestletProducerException(exchange, response, respCode));
                        } else {
                            binding.populateExchangeFromRestletResponse(exchange, response);
                        }
                    }
                } catch (Exception e) {
                    exchange.setException(e);
                }
            }
        });

        callback.done(false);
        return false;
    }

While debugging the route followin ginformation is outputted. Note where it says " Exchange processed and is continued routed asynchronously for exchangeId "

01:08:03.824   [qtp723059574-46] TRACE org.apache.camel.processor.Pipeline - Processing complete for exchangeId: ID-NB0629-50370-1395170917014-0-2 >>> Exchange[Message: [Body is instance of java.io.InputStream]]
01:08:03.825   [qtp723059574-46] TRACE o.a.c.p.CamelInternalProcessor - Exchange processed and is continued routed asynchronously for exchangeId: ID-NB0629-50370-1395170917014-0-2 -> Exchange[Message: [Body is instance of java.io.InputStream]]
01:08:03.831   [qtp723059574-46] TRACE org.apache.camel.processor.Pipeline - Processing exchangeId: ID-NB0629-50370-1395170917014-0-2 is continued being processed asynchronously
01:08:03.832   [qtp723059574-46] TRACE o.a.c.p.CamelInternalProcessor - **Exchange processed and is continued routed asynchronously for exchangeId**: ID-NB0629-50370-1395170917014-0-2 -> Exchange[Message: [Body is instance of java.io.InputStream]]
01:08:03.834   [qtp723059574-46] DEBUG o.a.c.c.r.DefaultRestletBinding - Populate Restlet response from exchange body: org.restlet.engine.io.UnclosableInputStream@c107903
Mar 19, 2014 1:08:03 AM org.restlet.engine.log.LogFilter afterHandle
INFO: 2014-03-19        01:08:03        0:0:0:0:0:0:0:1 -       0:0:0:0:0:0:0:1 8082    POST    /context/endpoint        -       200     -       66      221     http://localhost:8082   Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.154 Safari/537.36   -
01:08:06.251   [Restlet-1502737852] DEBUG o.a.c.c.restlet.RestletProducer - Received response: HTTP/1.1 - OK (200) - OK for exchangeId: ID-NB0629-50370-1395170917014-0-2
01:08:06.253   [Restlet-1502737852] DEBUG o.a.c.c.r.DefaultRestletBinding - Populate exchange from Restlet response header: org.restlet.virtualHost value: 344880096
01:08:06.254   [Restlet-1502737852] DEBUG o.a.c.c.r.DefaultRestletBinding - Populate exchange from Restlet response header: org.restlet.context value: org.restlet.Context@6675e3e5
01:08:06.254   [Restlet-1502737852] DEBUG o.a.c.c.r.DefaultRestletBinding - Populate exchange from Restlet response header: org.restlet.http.headers value: [[Set-Cookie: JSESSIONID=s5bnkehrfq2d1hd9mc2jz93rf;Path=/finnone-webapp], [Expires: Thu, 01 Jan 1970 00:00:00 GMT], [Content-Type: application/json;charset=UTF-8], [Transfer-Encoding: chunked], [Server: Jetty(8.1.12.v20130726)]]
01:08:06.307   [Restlet-1502737852] DEBUG o.a.c.c.r.DefaultRestletBinding - Populate exchange from Restlet response: { Your expected JSON response comes here}

Camel documents states here that several component use this async behaviour for scalability reasons but they can be forced to behave in synchronous manner by using synchronous=true in endpoint configuration. However unfortunately the restlet producer does not seem to be supporting this, as I cannot see any such URI option in their configuration here . Also having a look at the RestletComponent there seems to be no support for this.

On the other hand the Apache CXF component does have support for synchronous calls as mentioned in the list of URI options here .

Answer 2

In the Camel documentation , an example is given how Camel can be used as a HTTP proxy:

<route>
    <from uri="jetty:http://0.0.0.0:8080/myapp?matchOnUriPrefix=true"/>
    <to uri="jetty:http://realserverhostname:8090/myapp?bridgeEndpoint=true&amp;throwExceptionOnFailure=false"/>
 </route>