Are asynchronous RESTful web services possible?

Question

Reading RESTful documentation, it does not seem like it is possible to implement an asynchronous instance, but someone may know better on SO.

What I mean here is I would like to execute service requests asynchronously:

@Path("/helloworld", asyncSupported=true)
public class MyHelloWorldService {
    ...
}

I know asyncSupported is not defined in @Path, but I am looking for something similar to @WebServlet. Then, I would like to use AsyncContext instances (or anything equivalent).

Is this possible?

Solution 1

RestEasy has some support¹ for it - using a custom annotation called @Suspend.

See here: http://docs.jboss.org/resteasy/docs/2.2.1.GA/userguide/html/Asynchronous_HTTP_Request_Processing.html

There is also a framework/library on top of Jersey called Atmosphere however that might be overkill for your usecase as its focus appears to be on long-polling client/server web applications ( e.g. chats - https://github.com/Atmosphere/atmosphere )

[1] The CDI scope for your request will be lost in in the thread that actually executes the logic. See the RESTEasy-682 issue for more information. This is a problem that hasn't been solved by any REST frameworks that I know of at this moment^{[March 2014]}.

Solution 2

It's apparently possible with CXF and Jetty Continuations but that only appears to be possible with Jetty 6; they've been changed in Jetty 7 to something that's in the Servlet 3.0 spec and I don't know if that's supported by CXF. Moreover, Jetty Continuations seem to be a bit of a messy API, with a lot of manual stuff so I don't know how easy it is to convert the code.

Still, somewhat possible it seems. With a following breeze and when God wills it.

Solution 3

Now you can make Asynchoronous RESTful calls using JAX-RS 2.0 API which is part of the recently released Java EE 7.0

http://www.slideshare.net/reza_rahman/jaxrs2?ref=

Solution 4

Restful spesification is still at early ages of its life. But this problem should be considered as 2 part. Client and Server.

Client:

For the client side recent changes at last year became mature enough. And recently a non blocking client from based on Jeanfrancois Arcand was implemented and pushed to repository. There is an explanation here.

Server:

For the server side, it is still immature. The adoption of the new servlet specification is quite slow and as a developer I am expecting JSR 339 to address these issues as well. And this is also addressed at the JSR spec clearly with these sentences.

JAX-RS 1.1 defines a synchronous request response model on the server side. This JSR will specify a simple asynchronous request processing model such that a response can be returned asynchronous to the request. Servlet 3.0 can be leveraged to enable such support but implementations may choose to use other container-specific APIs instead.

However there are other alternatives too. Projects such as Jetty are addressing such kind of problems elegant as in this example. I can only suggest you to consider other alternatives as the community is growing.

Solution 5

Check out Pubsubhubbub found here for an example of a REST-based asynchronous protocol. It is based on the Atom Syndication format and is a lot simplier than WS-* pub/sub mechanisms.

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Comments

[Buhake Sindi]

Why not use AJAX to call your RESTful method asynchronously?

[Jérôme Verstrynge]

@The Because AsyncContext was implemented to solve the excessive thread-per-request issue in Servlet. Using Ajax to call RESTful would not tackle this issue (on the server side). The idea/solution is to queue requests for processing on a limited set of threads (a bit like Nginx).

[Jan Algermissen]

You might want to ask on the java.net/projects/jersey/lists/users/archive list. IIRC Jersey experimented with futures some time ago. Not sure whether that evolved.

[BillMan]

You may want to look something like Apache ServiceMix for inspiration.

[b_erb]

Are you asking whether this is possible in your library, or how to tackle asynchrony in REST interfaces in general?

[Jérôme Verstrynge]

@PartlyCloudy If I implement my RESTful service, can I generate and use an AsyncContext for each received request or not? That's what I am wondering...

[b_erb]

So you are asking about a specific Java-based implementation of a RESTful webservice, and not how to design an API and its resources for asynchronous patterns.

[Cemo]

Simply you can not. However the future version of the Restful Web Services for Java (JSR 339) will address these issues. I have also replied too.

[ravindrab]

have a look at this. spring.io/guides/gs/async-method

[Jérôme Verstrynge]

That's a Ruby solution, do you have the Java one?

[Jérôme Verstrynge]

When I refer to asynchronous, I mean asynchronous request processing on server side...