public class AsyncStateMachine
extends Object

Manages the state transitions for async requests.

 The internal states that are used are:
 DISPATCHED    - Standard request. Not in Async mode.
 STARTING      - ServletRequest.startAsync() has been called but the
                 request in which that call was made has not finished
                 processing.
 STARTED       - ServletRequest.startAsync() has been called and the
                 request in which that call was made has finished
                 processing.
 READ_WRITE_OP - Performing an asynchronous read or write.
 MUST_COMPLETE - complete() has been called before the request in which
                 ServletRequest.startAsync() has finished. As soon as that
                 request finishes, the complete() will be processed.
 COMPLETING    - The call to complete() was made once the request was in
                 the STARTED state. May or may not be triggered by a
                 container thread - depends if start(Runnable) was used
 TIMING_OUT    - The async request has timed out and is waiting for a call
                 to complete(). If that isn't made, the error state will
                 entered.
 MUST_DISPATCH - dispatch() has been called before the request in which
                 ServletRequest.startAsync() has finished. As soon as that
                 request finishes, the dispatch() will be processed.
 DISPATCHING   - The dispatch is being processed.
 ERROR         - Something went wrong.

 |-----------------»--------------|
 |                               \|/
 |   |----------«---------------ERROR---------------------------«-------------------------------|
 |   |      complete()         /|\ | \                                                          |
 |   |                          |  |  \---------------|                                         |
 |   |                          |  |                  |dispatch()                               |
 |   |                          |  |postProcess()    \|/                                        |
 |   |                   error()|  |                  |                                         |
 |   |                          |  |  |--|timeout()   |                                         |
 |   |           postProcess()  | \|/ | \|/           |         auto                            |
 |   |         |---------------»DISPATCHED«---------- | --------------COMPLETING«-----|         |
 |   |         |               /|\  |                 |                 | /|\         |         |
 |   |         |    |---»-------|   |                 |                 |--|          |         |
 |   |         ^    |               |startAsync()     |               timeout()       |         |
 |   |         |    |               |                 |                               |         |
 |  \|/        |    |  complete()  \|/  postProcess() |                               |         |
 | MUST_COMPLETE-«- | ----«------STARTING--»--------- | ------------|                 ^         |
 |  /|\    /|\      |               |                 |             |      complete() |         |
 |   |      |       |               |                 |             |     /-----------|         |
 |   |      |       ^               |dispatch()       |             |    /                      |
 |   |      |       |               |                 |             |   /                       |
 |   |      |       |              \|/                /            \|/ /    postProcess()       |
 |   |      |       |         MUST_DISPATCH          /           STARTED«---------«---------|   |
 |   |      |       |           |                   /           / |   |                     |   |
 |   |      |       |           |postProcess()     /           /  |   |                     ^   |
 ^   |      ^       |           |                 /           /   |   |asyncOperation()     |   |
 |   |      |       |           |                /           /    |   |                     |   |
 |   |      |       |           |   |---------- / ----------/     |   |--READ_WRITE_OP--»---|   |
 |   |      |       |           |   |          /   dispatch()     |            |  |  |          |
 |   |      |       |           |   |   |-----/               auto|            |  |  |   error()|
 |   |      |       | auto     \|/ \|/ \|/                        |  dispatch()|  |  |-»--------|
 |   |      |       |---«------DISPATCHING«--------«------------- | ------«----|  |
 |   |      |                      /|\                            |               |
 |   |      |                       |       dispatch()           \|/              |
 |   |      |                       |-----------------------TIMING_OUT            |
 |   |      |                                                 |   |               |
 |   |      |-------«----------------------------------«------|   |               |
 |   |                          complete()                        |               |
 |   |                                                            |               |
 |«- | ----«-------------------«-------------------------------«--|               |
     |                           error()                                          |
     |                                                  complete()                |
     |----------------------------------------------------------------------------|