How to : Async Callbacks using SOAP/REST Web Services with Java

We have a Java API that needs to be supplemented/fronted with a SOAP/REST Web service Layer.

What does it take to implement Async Calls across process/server boundaries using

a) SOAP Webservices

b) RESTf开发者_运维知识库ul webservices

Some of the methods might need multiple calls to respond to the request.

We will be using Java/J2ee to implement the SOAP/restful service using a library like CXF or Axis or    Jax-RS/WS.

Any examples ? Gotchas ?

Thank you,

The Async Http Client is an open source library that was specifically designed for this type of problem. It utilizes futures and wraps up a lot of the detail and hassle out of making async calls.

The author has a very good getting started guide and there is an active discussion group. The author is a very talented developer and the project is under continuous development.

From the documentation:

The library uses Java non blocking I/O for supporting asynchronous operations. The default asynchronous provider is build on top of Netty (http://www.jboss.org/netty), the Java NIO Client Server Socket Framework from JBoss, but the library exposes a configurable provider SPI which allows to easily plug in other frameworks.

Your question is not clear. I am interpreting your question as you want your serverside code to call a remote REST web services in an Async manner. If so then your best bet is to use the Futures feature of java.util.concurrent it will do exactly what you want. If my interpretation of the question is wrong then please update your question with exactly where the async operations need to happen.

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@Vivek

GET is async and other HTTP methods are not.

This isn't true. Please go ahead and read about AJAX :-)

For REST web services (apart from GET) everything else (POST/PUT..) is Async, it returns you the HTTP status code of the opeeration.

If you want to make GET also Async then you will have to use Threads, We did it once in Spring framework using @Async annotation (which internally spawns a thread).

From get return the callback URL as the response and use threads to process the request asynchronously.

Apart from that, For both SOAP / REST once you get the request you can publish it on a JMS queue to make the service Async.

One of the best ways to implement asynch ops is to use callbacks. For REST APIs, design of APIs and Rest client should support this. For instance , client class should pass itself or it's inner class as listner. Rest API on server side should maintain request id and call back listener in map . Once processing is done , it can call method on listener based on request id from map.

Real question: why do you want to call it Async? Having looked at solutions for parallel processing on the Java EE side, it's not recommended that you spawn child threads within a container on your own.

In your case, it looks like the following: 1. you're looking to create a wrapper contract in WSDL (REST or SOAP or both) and if you clients are not just browsers (AJAX)(i mean you'd have adopters from the server-side), then, for JAX-WS -> you could create a @CallBack end-ponint (http://docs.oracle.com/cd/E15051_01/wls/docs103/webserv_adv/callback.html) or
if it's REST end-point that requires being called from an adopter (server-side), use jAX_RS 2.0 feature

Note: Above assumes it's point to point but in an Async way

Here are a few options:

1. if you're looking to call REST Or SOAP or some other function asynchronously, you can use workManager API (JSR ) or
2. use JMS and use a request-reply model if you need it (short running) and calling multiple end-points in parallel
3. use WS-BPEL (only WSDL end-points) - this is a OASIS standard as well
4. use SCA (any component with any technology) that can contain assemblies of WS-BPEL component (stateless or stateful) running in BPEL engine like Apache ODE or IBM process server and other components and collaborates. This is a standard