Interface KieSession

  • All Superinterfaces:
    CommandExecutor, EntryPoint, KieRuntime, KieRuntimeEventManager, ProcessEventManager, ProcessRuntime, RuleRuntime, RuleRuntimeEventManager, StatefulProcessSession, StatefulRuleSession

    public interface KieSession
    extends StatefulRuleSession, StatefulProcessSession, CommandExecutor, KieRuntime
    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 );

    Simple example showing a stateful session executing processes.

     KieSession kSession = kbase.newKieSession();
     kSession.signalEvent("SomeEvent", null);

    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:

     KieSession ksession = kbase.newKieSession();
     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.

    Like StatelessKieSession this also implements CommandExecutor which can be used to script a KieSession. See CommandExecutor for more details.

    See Also:
    • Method Detail

      • getId

        int getId()
        Deprecated. use getIdentifier() instead
        id of this session
      • getIdentifier

        long getIdentifier()
      • dispose

        void dispose()
        Releases all the current session resources, setting up the session for garbage collection. This method must always be called after finishing using the session, or the engine will not free the memory used by the session. If a logger has been registered on this session it will be automatically closed.
      • destroy

        void destroy()
        Destroys session permanently. In case of session state being persisted in data store it will be removed from it otherwise it falls back to default dispose() method. NOTE: Name and location of this method will most likely change before 6.0.Final as it applies only to persistent sessions
      • submit

        void submit​(KieSession.AtomicAction action)
        Submit an action that will be executed atomically on this session. This is useful when using fireUntilHalt to avoid evaluations against partially modified objects.
      • getKieRuntime

        <T> T getKieRuntime​(java.lang.Class<T> cls)
        Returns a runtime for the given interface. This method is used to retrieve runtime extensions to the engine. It is used as the hook point for the custom pluggable knowledge extensions like the bayes engine and the DMN engine. E.g.: DMNRuntime dmnRuntime = session.getKieRuntime( DMNRuntime.class );
        cls - the runtime interface for the extension
        the runtime instance for the extension