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https://issues.apache.org/activemq/browse/CAMEL-2026?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=56769#action_56769
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Hadrian Zbarcea commented on CAMEL-2026:
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Exactly. Plus bam has it's own dsl, which could be extended.
I think your use case makes sense, and we are always interested in improving
camel and support useful scenarios. The question is where in camel is best to
plug in new functionality. The part I, personally, am not very fond of is the
XA transactions. I think they are very brittle and too resource intensive with
long running transactions, but that's just my opinion. Thread management/admin
stuff does belong in camel.
We also highly appreciate contributions. Kudos for taking the time and send
some code.
> Enable async request-reply by enhancing the CamelInvocationHandler so that it
> is serializable, so that camel-spring Proxies can be passed as callback
> objects
> -------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: CAMEL-2026
> URL: https://issues.apache.org/activemq/browse/CAMEL-2026
> Project: Apache Camel
> Issue Type: Improvement
> Components: camel-core, camel-spring
> Affects Versions: 2.0.0
> Reporter: Scott Clasen
> Assignee: Claus Ibsen
> Fix For: 2.2.0
>
> Attachments: camel-2026.zip
>
>
> With minor alteration, the CamelInvocationHandler could be made serializable,
> and then camel-spring bean proxies could be passed as callback objects in
> method calls on other camel-spring proxies...enabling async request-reply via
> spring remoting.
> I have achieved this by Wrapping the CamelInvocationHandler, subclassing the
> CamelProxyFactoryBean, and by attaching a processor to routes that can
> recieve BeanInvocations that have a callback object. Integrated into the
> codebase, this could be much more straightforward, and not require a
> processor be attached.
> =================CamelInvocationHandlerWrapper
> {code}
> /**
> * Serializable wrapper for Camel/Spring remoting proxies.
> */
> public class CamelInvocationHandlerWrapper implements InvocationHandler,
> Serializable {
> /*
> Findbugs will complain that inner dosent get set at deserialization time.
> This is ok.
> You need to have a CamelRemotingProcessor in your inbound camel route that
> will reset the handler.
> */
> private transient CamelInvocationHandler inner;
> private String serviceUrl;
> private static final long serialVersionUID = 7635312279175935612L;
> /**
> * Create a CamelInvocationHandlerWrapper.
> *
> * @param handler the handler to use in this VM.
> * @param serviceUrl the serviceUrl to use to rebuild the
> CamelInvocationHandler if we are serialized and used in a different VM.
> */
> public CamelInvocationHandlerWrapper(CamelInvocationHandler handler,
> String serviceUrl) {
> this.inner = handler;
> this.serviceUrl = serviceUrl;
> }
> /**
> * {...@inheritdoc}
> */
> public Object invoke(Object proxy, Method method, Object[] args) throws
> Throwable {
> if (method.getDeclaringClass().equals(Object.class)) {
> return method.invoke(this, args);
> } else {
> if (inner == null) {
> throw new IllegalStateException("The inner
> CamelInvocationHandler is null, perhaps there was no CamelRemotingProcessor
> on your inbound route???");
> } else {
> return inner.invoke(proxy, method, args);
> }
> }
> }
> /**
> * Package Private so the CamelRemotingProcessor can rewire when we are
> passed remotely.
> *
> * @param context the current camel context.
> * @throws Exception if we cant build an endpoint for the service url or
> create a producer.
> */
> void rebuildInvocationHandler(CamelContext context) throws Exception {
> Endpoint endpoint = CamelContextHelper.getMandatoryEndpoint(context,
> serviceUrl);
> Producer producer = endpoint.createProducer();
> producer.start();
> inner = new CamelInvocationHandler(endpoint, producer, new
> MethodInfoCache(endpoint.getCamelContext()));
> }
> void setServiceUrl(String serviceUrl) {
> this.serviceUrl = serviceUrl;
> }
> }
> {code}
> ================Proxy Factory
> {code}
> /**
> * ProxyFactory that wraps a camel proxy in a serializable form.
> */
> public class CamelProxyWrapperFactoryBean extends CamelProxyFactoryBean {
> /**
> * Override the CamelProxyFactoryBean to return a different proxy that
> uses a CamelInvocationHandlerWrapper.
> *
> * @return a Proxy backed by a CamelInvocationHandlerWrapper for the
> specified interface.
> * @throws Exception if we cant create the proxy.
> */
> @Override
> public Object getObject() throws Exception {
> Object proxy = super.getObject();
> CamelInvocationHandler handler = (CamelInvocationHandler)
> Proxy.getInvocationHandler(proxy);
> return Proxy.newProxyInstance(getObjectType().getClassLoader(), new
> Class[]{getObjectType()}, new CamelInvocationHandlerWrapper(handler,
> getServiceUrl()));
> }
> }
> {code}
> ========processor that "rewires" the transient CamelInvocationHandler by
> using the service url
> {code}
> public class CamelRemotingProcessor implements Processor {
> /**
> * Rebuild the CamelInvocationHandler if we were passed a Proxy that has
> a CamelInvocationHandlerWrapper as its handler.
> *
> * @param invocation the BeanInvocation whose args we check for the Proxy.
> * @param context the current Camel Context.
> * @throws Exception if something blows up.
> */
> public void rewireProxy(BeanInvocation invocation, CamelContext context)
> throws Exception {
> Object[] args = invocation.getArgs();
> if (args != null) {
> for (Object arg : args) {
> if (Proxy.isProxyClass(arg.getClass())) {
> InvocationHandler handler =
> Proxy.getInvocationHandler(arg);
> if (handler instanceof CamelInvocationHandlerWrapper) {
> CamelInvocationHandlerWrapper wrapper =
> (CamelInvocationHandlerWrapper) handler;
> wrapper.rebuildInvocationHandler(context);
> }
> }
> }
> }
> }
> /**
> * {...@inheritdoc}
> */
> public void process(Exchange exchange) throws Exception {
> CamelContext context = exchange.getContext();
> BeanInvocation invocation =
> exchange.getIn().getBody(BeanInvocation.class);
> rewireProxy(invocation, context);
> }
> }
> {code}
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