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RE: [Smartfrog-developer] Question for EventSend and OnEvent components
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From: Julio G. <ju...@us...> - 2004-05-26 23:14:18
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Hi Qinyi,
You are making a correct use of EvenSent. Your problem is that you are =
sending an event to a component that does not exist yet. e1 and comp1 =
are in a Sequence and therefore comp1 won't be deployed until e1 has =
terminated.
If you replace Sequence with Parallel your example will work.
Parallel will deploy all its children and it will terminate when all its =
children have terminated.
There is another example in examples/workflow that you can use.
We are planning make some changes in the workflow components and that is =
why you haven't seen any documentation for the workflow yet.=20
Some info about those components:
DoNothing
DoNothing extends EventPrim {
sfClass "com.hp.sfServices.workflow.Components.DoNothing";
time 10000000; // time in milliseconds to wait
terminationType "normal"; // termination record type
printEvents false;
// message "a message to print on the console prefixed by full name"
}
The do-nothing construct does nothing for a time, then terminates as =
required. Its purpose is primarily to act as a stub for bits of workflow =
yet to be written during testing. If terminationType is set to "none", =
it waits for ever.
The component prints the message to stdout and starts the timer during =
its start phase and terminates when the timer has fired. If the time is =
0, the component will terminate immediately - though a thread is started =
to do this so some asynchrony occurs. If no message is provided, no =
message is printed.
If the attribute printEvents is set to true, any events that it receives =
will be printed on the console. If printEvents is false, it does nothing =
internal with events, merely forwarding them as required.
EventSend
EventSend extends EventPrim {
sfClass "com.hp.sfServices.workflow.Components.EventSend";
// event "the string to send as an event";=20
}
An event sender contains an event to send, and it forwards the event to =
any registered components as defined in the event framework.
The component sends its event during the start phase, and then =
terminates asynchronously. It does nothing internal with received =
events.
EventCounter
EventCounter extends EventPrim {
sfClass "com.hp.sfServices.workflow.Components.EventCounter";
count 1;
allDifferent "true";
}
Event counter waist for events, when they arrive it decrements its =
counter (default 1). When the counter reaches 0, the component =
terminates. If the attribute allDifferent is set to true, the counter is =
not decremented if the event it receives is an identical string.
OnEvent
OnEvent extends EventCompound {
sfClass "com.hp.sfServices.workflow.Components.OnEvent";
//event1 extends LAZY ... { ... }
//event2 extends LAZY ... { ... }
//otherwise extends LAZY ... { ... } } The OnEvent event dispatcher =
provides a number of named event handlers as attributes - defined as =
LAZY components. When an event arrives, it is compared to the names of =
the attributes using Java string equality, and if a matching attribute =
is found the component description is taken and deployed.
If no match is found, the otherwise template is taken. If that is not =
present, the component terminates with an error.
Once a handler has been started, it runs as the newly created =
sub-component as a child using the name running. When that child =
terminates, so does the OnEvent, with the same termination type.
Regards,=20
Julio Guijarro
> -----Original Message-----
> From: sma...@li...=20
> [mailto:smartfrog- dev...@li...] On Behalf Of =
> qx...@cc...
> Sent: 26 May 2004 19:56
> To: sma...@li...
> Subject: [Smartfrog-developer] Question for EventSend and OnEvent=20
> components
>=20
> Hi,
> I want to use the Events mechanism in SF to exchange message between=20
> different components. Two insteresting components are EventSend and=20
> OnEvent. But I cannot find an example of how to use them. The only=20
> place I could get some hints for EventSend is in=20
> genericInstallScript.sf in dynamicWebserver example. However, when I =
wrote a component like:
> ------------------------------------------------------------
> #include "org/smartfrog/sfcore/workflow/components.sf";
> #include "org/smartfrog/components.sf"
>=20
>=20
> event1 extends Sequence {
> name "test";
>=20
> actions extends LAZY {
> e1 extends EventSend {
> sendTo:a LAZY ATTRIB comp1;
> event (name);
> }
> comp1 extends DoNothing {
> time 2000;
> message "here";
> }
>=20
> }
> }
>=20
> sfConfig extends event1;
> ------------------------------------------------------------
>=20
> It can be parsed successful. But when I used sfStart to deploy it, the =
> following error message was thrown:
>=20
> $ sfStart localhost e event.sf
> SmartFrog 3.02.002_beta
> (C) Copyright 1998-2004 Hewlett-Packard Development Company, LP
> Warning: SmartFrog security is NOT active
> - FAILED when trying DEPLOY of 'e', [event.sf], host:localhost
> Error:
> SmartFrogLifecycleException:: sfStart:
> cause: SmartFrogResolutionException:: Reference not found,=20
> Unresolved
> Reference: LAZY comp1, source: HOST
> athena.cc.gatech.edu:rootProcess:e, path(83)
> Command line SFACT: 'e:DEPLOY:event.sf::localhost:'
> To String: ' name:e, type:DEPLOY, url:event.sf, host:localhost,=20
> resultType:FAILED, resultExceptionMessage:sfStart: '
>=20
> Is there anyone who can show me an example how to use these two=20
> components?
>=20
> Thanks
> Qinyi
>=20
>=20
>=20
>=20
>=20
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