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public interface KieSession
KieSession is the most common way to interact with the engine. A KieSession
allows the application to establish an iterative conversation with the engine, where the state of the
session is kept across invocations. The reasoning process may be triggered multiple times for the
same set of data. After the application finishes using the session, though, it must call the
dispose()
method in order to free the resources and used memory.
Simple example showing a KieSession executing rules for a given collection of java objects.
KieServices kieServices = KieServices.Factory.get(); KieContainer kContainer = kieServices.getKieClasspathContainer(); KieSession kSession = kContainer.newKieSession(); for( Object fact : facts ) { kSession.insert( fact ); } kSession.fireAllRules(); kSession.dispose();
Simple example showing a stateful session executing processes.
KieSession kSession = kbase.newStatefulKnowledgeSession(); kSession.startProcess("com.sample.processid"); kSession.signalEvent("SomeEvent", null); kSession.startProcess("com.sample.processid"); kSession.dispose();
KieSession support globals. Globals are used to pass information into the engine (like data or service callbacks that can be used in your rules and processes), but they should not be used to reason over. If you need to reason over your data, make sure you insert it as a fact, not a global.
Globals are shared among ALL your rules and processes, so be especially careful of (and avoid
as much as possible) mutable globals. Also, it is a good practice to set your globals before
inserting your facts or starting your processes. Rules engines evaluate rules at fact insertion
time, and so, if you are using a global to constraint a fact pattern, and the global is not set,
you may receive a NullPointerException
.
Globals can be resolved in two ways. The KieSession supports getGlobals() which returns the internal Globals, which itself can take a delegate. Calling of setGlobal(String, Object) will set the global on an internal Collection. Identifiers in this internal Collection will have priority over the externally supplied Globals delegate. If an identifier cannot be found in the internal Collection, it will then check the externally supplied Globals delegate, if one has been set.
Code snippet for setting a global:
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); ksession.setGlobal( "hbnSession", hibernateSession ); // sets a global hibernate session, that can be used for DB interactions in the rules. for( Object fact : facts ) { ksession.insert( fact ); } ksession.fireAllRules(); // this will now execute and will be able to resolve the "hbnSession" identifier. ksession.dispose();
Like StatelessKieSession this also implements CommandExecutor which can be used to script a KieSession. See CommandExecutor for more details.
org.drools.core.runtime.Globals
Method Summary | |
---|---|
void |
destroy()
Destroys session permanently. |
void |
dispose()
Releases all the current session resources, setting up the session for garbage collection. |
int |
getId()
|
Methods inherited from interface org.kie.api.runtime.rule.StatefulRuleSession |
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fireAllRules, fireAllRules, fireAllRules, fireAllRules, fireUntilHalt, fireUntilHalt |
Methods inherited from interface org.kie.api.runtime.CommandExecutor |
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execute |
Methods inherited from interface org.kie.api.runtime.KieRuntime |
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getCalendars, getChannels, getEnvironment, getGlobal, getGlobals, getKieBase, getSessionClock, getSessionConfiguration, registerChannel, setGlobal, unregisterChannel |
Methods inherited from interface org.kie.api.runtime.rule.Session |
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getAgenda, getEntryPoint, getEntryPoints, getQueryResults, halt, openLiveQuery |
Methods inherited from interface org.kie.api.runtime.rule.SessionEntryPoint |
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delete, getEntryPointId, getFactCount, getFactHandle, getFactHandles, getFactHandles, getObject, getObjects, getObjects, insert, retract, update |
Methods inherited from interface org.kie.api.runtime.process.ProcessRuntime |
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abortProcessInstance, createProcessInstance, getProcessInstance, getProcessInstance, getProcessInstances, getWorkItemManager, signalEvent, signalEvent, startProcess, startProcess, startProcessInstance |
Methods inherited from interface org.kie.api.event.rule.WorkingMemoryEventManager |
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addEventListener, addEventListener, getAgendaEventListeners, getWorkingMemoryEventListeners, removeEventListener, removeEventListener |
Methods inherited from interface org.kie.api.event.process.ProcessEventManager |
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addEventListener, getProcessEventListeners, removeEventListener |
Method Detail |
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int getId()
void dispose()
void destroy()
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