I am analyzing some jersey 2.0 code and i have a question on how the following method works:
@Stateless
@Path("/mycoolstuff")
public class MyEjbResource {
…
@GET
@Asynchronous //does this mean the method executes on child thread ?
public void longRunningOperation(@Suspended AsyncResponse ar) {
final String result = executeLongRunningOperation();
ar.resume(result);
}
private String executeLongRunningOperation() { … }
}
Lets say im at a web browser and i type in www.mysite/mycoolstuff this will execute the method but im not understanding what the asyncResponse is used for neither the @Asynchronous annotation. From the browser how would i notice its asychnronous ? what would be the difference in removing the annotation ? Also the suspended annotation after reading the documentation i'm not clear its purpose.
is the @Asynchronous annotation simply telling the program to execute this method on a new thread ? is it a convenience method for doing "new Thread(.....)" ?
Update: this annotation relieves the server of hanging onto the request processing thread. Throughput can be better. Anyway from the official docs:
Request processing on the server works by default in a synchronous processing mode, which means that a client connection of a request is processed in a single I/O container thread. Once the thread processing the request returns to the I/O container, the container can safely assume that the request processing is finished and that the client connection can be safely released including all the resources associated with the connection. This model is typically sufficient for processing of requests for which the processing resource method execution takes a relatively short time. However, in cases where a resource method execution is known to take a long time to compute the result, server-side asynchronous processing model should be used. In this model, the association between a request processing thread and client connection is broken. I/O container that handles incoming request may no longer assume that a client connection can be safely closed when a request processing thread returns. Instead a facility for explicitly suspending, resuming and closing client connections needs to be exposed. Note that the use of server-side asynchronous processing model will not improve the request processing time perceived by the client. It will however increase the throughput of the server, by releasing the initial request processing thread back to the I/O container while the request may still be waiting in a queue for processing or the processing may still be running on another dedicated thread. The released I/O container thread can be used to accept and process new incoming request connections.
@Suspended have more definite if you used it, else it will not make any difference of using it.
Let's talk about benefits of it:
@Suspended, and even provide a fall back response when time get exceed.Below is some sample of code for setting suspend/pause timeout
public void longRunningOperation(@Suspended AsyncResponse ar) {
ar.setTimeoutHandler(customHandler);
ar.setTimeout(10, TimeUnit.SECONDS);
final String result = executeLongRunningOperation();
ar.resume(result);
}