org.drools.runtime.StatelessKnowledgeSession Maven / Gradle / Ivy
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/*
* Copyright 2010 JBoss Inc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.drools.runtime;
import org.drools.command.Command;
import org.drools.command.CommandFactory;
import org.drools.event.KnowledgeRuntimeEventManager;
import org.drools.runtime.process.StatelessProcessSession;
import org.drools.runtime.rule.StatelessRuleSession;
/**
* StatelessKnowledgeSession provides a convenience API, wrapping StatefulKnowledgeSession. It avoids the need to
* call dispose(). Stateless sessions do not support
* iterative invocations, the act of calling execute(...) is a single
* shot method that will internally instantiate a StatefulKnowledgeSession, add all the user data and execute user commands, call fireAllRules, and then
* call dispose(). While the main way to work with this class is via the BatchExecution Command as supported by the CommandExecutor interface,
* two convenience methods are provided for when simple object insertion is all that's required.
*
*
* Simple example showing a stateless session executing for a given collection of java objects using the convenience api. It will iterate the collection inserting
* each element in turn
*
*
* KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
* kbuilder.add( ResourceFactory.newFileSystemResource( fileName ), ResourceType.DRL );
* assertFalse( kbuilder.hasErrors() );
* if (kbuilder.hasErrors() ) {
* System.out.println( kbuilder.getErrors() );
* }
* KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
* kbase.addKnowledgePackages( kbuilder.getKnowledgePackages() );
*
* StatelessKnowledgeSession ksession = kbase.newStatelessKnowledgeSession();
* ksession.execute( collection );
*
*
*
* If this was done as a single Command it would be as follows:
*
*
* ksession.execute( CommandFactory.newInsertElements( collection ) );
*
*
*
* Note if you wanted to insert the collection itself, and not the iterate and insert the elements, then CommandFactory.newInsert( collection ) would do the job.
*
*
*
* The CommandFactory details the supported commands, all of which can be marshalled using XStream and the BatchExecutionHelper. BatchExecutionHelper provides details
* on the XML format as well as how to use Drools Pipeline to automate the marshalling of BatchExecution and ExecutionResults.
*
*
*
* StatelessKnowledgeSessions support globals, scoped in a number of ways. I'll cover the non-command way first,
* as commands are scoped to a specific execution call. Globals can be resolved in three ways. The StatelessKnowledgeSession
* supports getGlobals(), which returns a Globals instance. These globals are shared for ALL execution calls, so be especially careful of mutable
* globals in these cases - as often execution calls can be executing simultaneously in different threads. Globals also supports a delegate, which
* adds a second way of resolving globals. Calling of setGlobal(String, Object) will actually be set on an internal Collection, identifiers in this internal
* Collection will have priority over supplied delegate, if one is added. If an identifier cannot be found in
* the internal Collection, it will then check the delegate Globals, if one has been set.
*
*
* Code snippet for setting a session scoped global:
*
* StatelessKnowledgeSession ksession = kbase.newStatelessKnowledgeSession();
* ksession.setGlobal( "hbnSession", hibernateSession ); // sets a global hibernate session, that can be used for DB interactions in the rules.
* ksession.execute( collection ); // this will now execute and will be able to resolve the "hbnSession" identifier.
*
*
*
* The third way is execution scopped globals using the CommandExecutor and SetGlobal Commands:
*
*
*
* List cmds = new ArrayList();
* cmds.add( CommandFactory.newSetGlobal( "list1", new ArrayList() ) );
* cmds.add( CommandFactory.newInsert( new Person( "jon", 102 ) ) );
*
* ksession.execute( CommandFactory.newBatchExecution( cmds ) );
*
*
*
* The CommandExecutor interface also supports the ability to export data via "out" parameters. Inserted facts, globals and query results can all be returned.
*
*
*
* List cmds = new ArrayList();
* cmds.add( CommandFactory.newSetGlobal( "list1", new ArrayList(), true ) );
* cmds.add( CommandFactory.newInsert( new Person( "jon", 102 ), "person" ) );
* cmds.add( CommandFactory.newQuery( "Get People" "getPeople" );
*
* ExecutionResults results = ksession.execute( CommandFactory.newBatchExecution( cmds ) );
* results.getValue( "list1" ); // returns the ArrayList
* results.getValue( "person" ); // returns the inserted fact Person
* results.getValue( "Get People" );// returns the query as a QueryResults instance.
*
*
*
* @see org.drools.runtime.CommandExecutor
* @see org.drools.runtime.command.CommandFactory
* @see org.drools.runtime.command.BatchExecution
* @see org.drools.runtime.ExecutionResults.BatchExecutionResults
* @see org.drools.runtime.help.BatchExecutionHelp
* @see org.drools.runtime.pipeline.PipelineFactory
* @see org.drools.runtime.Globals
*/
public interface StatelessKnowledgeSession
extends
StatelessRuleSession,
StatelessProcessSession,
CommandExecutor,
KnowledgeRuntimeEventManager {
/**
* Return the Globals store
*/
Globals getGlobals();
/**
* Sets a global value on the globals store
* @param identifer the global identifier
* @param value the value assigned to the global identifier
*/
void setGlobal(String identifer,
Object value);
}