66 lines
2.6 KiB
ReStructuredText
66 lines
2.6 KiB
ReStructuredText
|
||
.. _howto-java:
|
||
|
||
######################
|
||
HowTo: Common Patterns
|
||
######################
|
||
|
||
This section lists common actor patterns which have been found to be useful,
|
||
elegant or instructive. Anything is welcome, example topics being message
|
||
routing strategies, supervision patterns, restart handling, etc. As a special
|
||
bonus, additions to this section are marked with the contributor’s name, and it
|
||
would be nice if every Akka user who finds a recurring pattern in his or her
|
||
code could share it for the profit of all. Where applicable it might also make
|
||
sense to add to the ``akka.pattern`` package for creating an `OTP-like library
|
||
<http://www.erlang.org/doc/man_index.html>`_.
|
||
|
||
You might find some of the patterns described in the Scala chapter of
|
||
:ref:`howto-scala` useful even though the example code is written in Scala.
|
||
|
||
Scheduling Periodic Messages
|
||
============================
|
||
|
||
This pattern describes how to schedule periodic messages to yourself in two different
|
||
ways.
|
||
|
||
The first way is to set up periodic message scheduling in the constructor of the actor,
|
||
and cancel that scheduled sending in ``postStop`` or else we might have multiple registered
|
||
message sends to the same actor.
|
||
|
||
.. note::
|
||
|
||
With this approach the scheduled periodic message send will be restarted with the actor on restarts.
|
||
This also means that the time period that elapses between two tick messages during a restart may drift
|
||
off based on when you restart the scheduled message sends relative to the time that the last message was
|
||
sent, and how long the initial delay is. Worst case scenario is ``interval`` plus ``initialDelay``.
|
||
|
||
.. includecode:: code/docs/pattern/SchedulerPatternTest.java#schedule-constructor
|
||
|
||
The second variant sets up an initial one shot message send in the ``preStart`` method
|
||
of the actor, and the then the actor when it receives this message sets up a new one shot
|
||
message send. You also have to override ``postRestart`` so we don't call ``preStart``
|
||
and schedule the initial message send again.
|
||
|
||
.. note::
|
||
|
||
With this approach we won't fill up the mailbox with tick messages if the actor is
|
||
under pressure, but only schedule a new tick message when we have seen the previous one.
|
||
|
||
.. includecode:: code/docs/pattern/SchedulerPatternTest.java#schedule-receive
|
||
|
||
Template Pattern
|
||
================
|
||
|
||
*Contributed by: N. N.*
|
||
|
||
This is an especially nice pattern, since it does even come with some empty example code:
|
||
|
||
.. includecode:: code/docs/pattern/JavaTemplate.java
|
||
:include: all-of-it
|
||
:exclude: uninteresting-stuff
|
||
|
||
.. note::
|
||
|
||
Spread the word: this is the easiest way to get famous!
|
||
|
||
Please keep this pattern at the end of this file.
|