[jboss-dev-forums] [Design of JBoss ESB] - Re: Supporting entry-point

[beve]

As an example of entry point usage (from the Drools Fusion User Guide):
rule "apply fee on withdraws on branches"
  | when
  |     WithdrawRequest( $ai : accountId, processed == true ) from entry-point "Branch Stream"
  |     CheckingAccount( accountId == $ai )
  | then
  |     // apply a $2 fee on the account
  | end
Instead of inserting events directly into the working memory, you insert them into the entry point as shown in the following example:
// create your rulebase and your session as usual
  | StatefulKnowledgeSession session = ...
  | 
  | // get a reference to the entry point
  | WorkingMemoryEntryPoint atmStream = session.getWorkingMemoryEntryPoint( "ATM Stream" );
  | 
  | // and start inserting your facts into the entry point
  | atmStream.insert( aWithdrawRequest );
By requesting the WorkingMemoryEntryPoint from the session we are able to insert our facts into it and this will be separate from the "default" working memory.

In the ESB will want to give users the ability to use entry points in thier rules. To do this we need to let them specify which objects(facts) should be inserted in to the separate entry-points. Currently all are inserted in the the working memory (which I understand is simply a WorkingMemoryEntryPoint named "DEFAULT").

Burr suggested that the following configuration option to be added:
<object-path esb="body.TheOrderHeader" entry-point="OrderStream" />
And this would result in something like this in the ESB code base:
WorkingMemoryEntryPoint atmStream = session.getWorkingMemoryEntryPoint( "OrderStream" );
  | atmStream.insert(orderHeader);
  | 

Burr also mentioned that we should support the ability to set the startTimeStamp on an event:
anonymous wrote : The date time stamp should be based on message DOB but perhaps overrideable here as well
Every event in Drools has an associated timestamp assigned which by default is read from Session Clock. 
This startTimeStamp is assigned to the event at the time the event is inserted into the working memory. 
But you are given the opportunity to have Drools use a different timestamp, for instance the DOB of the ESB Message object, by specifying that the timestamp of the fact being should be used instead:
@timestamp( <attributeName> )
So if we specified dob as the attribute name, the object being inserted is expected to have a field named dob, and that that field contains the timestamp that will be used when creating the EventFactHandle.
Just how this is going to look I don't know at the moment and I'd need to look into this and try it out.




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