12.10. Declaring and Using Entry Points

Entry points are declared implicitly by making direct use of them in rules. Referencing an entry point in a rule will make the engine, at compile time, identify and create the proper internal structures to support that entry point.
For example, a banking application that has transactions fed into the engine via streams could have one stream for all of the transactions executed at ATMs. A rule for this scenario could state, "A withdrawal is only allowed if the account balance is greater than the withdrawal amount the customer has requested."

Example 12.8. Example ATM Rule

rule "authorize withdraw"
   when
       WithdrawRequest( $ai : accountId, $am : amount ) from entry-point "ATM Stream"
       CheckingAccount( accountId == $ai, balance > $am )
   then
       // authorize withdraw
   end
When the engine compiles this rule, it will identify that the pattern is tied to the entry point "ATM Stream." The engine will create all the necessary structures for the rule-base to support the "ATM Stream", and this rule will only match WithdrawRequest events coming from the "ATM Stream."
Note the ATM example rule joins the event (WithdrawalRequest) from the stream with a fact from the main working memory (CheckingAccount).
The banking application may have a second rule that states, "A fee of $2 must be applied to a withdraw request made via a branch teller."

Example 12.9. Using Multiple Streams

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
This rule matches events of the same type (WithdrawRequest) as the example ATM rule but from a different stream. Events inserted into the "ATM Stream" will never match the pattern on the second rule, which is tied to the "Branch Stream;" accordingly, events inserted into the "Branch Stream" will never match the pattern on the example ATM rule, which is tied to the "ATM Stream".
Declaring the stream in a rule states that the rule is only interested in events coming from that stream.
Events can be inserted manually into an entry point instead of directly into the working memory.

Example 12.10. Inserting Facts into an Entry Point

   // create your rulebase and your session as usual
   KieSession 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 );
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