Apache Camel: access both request and reply message at end of route

Simply store the original body of the in message in a header or a property and retrieve it at the end:

from("activemq:queue:myQueue")
.setProperty("origInBody", body())
.to("http://localhost:8080/someBackend")

After the http call you can then access the property origInBody.

First, this article shows very well how in and out works in camel: http://camel.apache.org/using-getin-or-getout-methods-on-exchange.html

Typically, the out message is not always used, but rather copied from the in-message in each step.

In your case, where you want the original message to stay around til the end of the route, you could go ahead with the Enrichment EIP. http://camel.apache.org/content-enricher.html

Your route would be something like this:

public class MyAggregationStrategy implements AggregationStrategy {
  public Exchange aggregate(Exchange orig, Exchange httpExchange){
    // if you want to check something with the Http request, you better do that here 
    if( httpExchange is not correct in some way ) 
       throw new RuntimeException("Something went wrong");

    return orig;
  }
}

AggregationStrategy aggStrategy = new MyAggregationStrategy();

from("activemq:queue:myQueue")
  .enrich("http://localhost:8080/someBackend",aggStrategy)
  .//keep processing the original request here if you like, in the "in" message

One of the biggest problem of camel, is the ease to misuse it. The best way to use it correctly is to think in terms of EIP : one of the main goals of camel, is to implement EIP in its DSL.

Here is a list of EIP

Now think about it. You want the request and the response at the end, for what use ? Logging, Aggregation, ... ? For logging, a correlationId should suffice, so I presume you need it to create a response, based on both request and the proxied-response. If that's what you want, you could do something like

from("direct:receiveRequest")
   .enrich("direct:proxyResponse", new RequestAndResponseAggregationStrategy())

You will have the opportunity to merge your Request (in oldExchange) and your Response (in newExchange).

With all the due respect I have for Christian Schneider, I do think the idea of putting the request in a property that could be reused later is a bad design. By doing it, you create side-effect between your routes. If your route is a subroute for another, you'll maybe erase their property. If you store it to put it back later, maybe you should do something like

from("direct:receiveRequest")
    .enrich("direct:subRouteToIgnoreResponse", AggregationStrategies.useOriginal())

A really really bad design that I have done too many time myself is to do :

from("direct:receiveRequest")
    .to("direct:subroute")

from("direct:subroute")
    .setProperty("originalBody", body())
    .to("direct:handling")
    .transform(property("originalBody")

This will lead to "properties/headers hell", and to routes that are just a successive call of processors.

And if you can't think of a solution of your problem with EIP, you should maybe use camel only to access their components. For example, something like :

from("http://api.com/services")
   .to(new SomeNotTranslatableToEIPProcessor())
   .to("ftp://destination")

But don't forget that those components has their own goals : creating a common abstraction between similar behaviour (e.g, time based polling consumer). If you have a very specific need, trying to bend a camel component to this specific need can lead to huge chunk of code not easily maintainable.

Don't let Camel become your Golden Hammer anti-pattern