what is Jersey's @ManagedAsync annotation?

Question

Would anyone please explain the meaning of the @ManagedAsync annotation? What does it do?

From the documentation (https://jersey.java.net/apidocs/2.21/jersey/org/glassfish/jersey/server/ManagedAsync.html):

Indicates that the resource method to which the annotation has been applied should be executed on a separate thread managed by an internal Jersey executor service.

Are not resources executed on separate threads anyway? I am confused.

Answer 1

@ManagedAsync is used for making a jersey resource asynchronous. It means that complete resource execution is done in another thread, not in the main thread in which request is received.

There are 2 ways for making asynchronous jersey resource -

1) Using @Suspended on AsyncResponse asyncResponse - But in this case, you have to create your own thread in code and execute expensive task in that thread.

2) Using @ManagedAsync - In this case, there is no need to create new thread manually, jersey creates thread and execute resource method in that thread.

More information can be found at Async Rest