"The api prescribes a set of fundamental rule engine operations. The set of operations is based upon the assumption that most clients will need to be able to execute a basic multi-step rule engine cycle, which consists of parsing rules, adding objects to an engine, firing rules and getting resultant objects from the engine. The set of operations also supports variations of the basic cycle, particularly variations that would occur in J2EE server deployments."
Goals:
Facilitate adding rule engine technology to Java applications.
Increase communication and standardization between rule engine vendors.
Make Java applications more portable from one rule engine vendor to another.
Provide implementation patterns for rules-based applications for the J2SE
platform.
Support rule engine vendors by offering a harmonized API that meets the needs
of their existing customers and is easily implemented.
Architecture:
The interfaces and classes defined by the specification are in the javax.rules and
javax.rules.admin packages. The javax.rules package contains classes and
interfaces that are aimed at runtime clients of the rule engine. The runtime client API
exposes methods to acquire a rule session for a registered rule execution set and
interact with the rule session. The administrator API-javax.rules.admin exposes methods to load an execution set from these external resources: URI, InputStream, XML Element,
binary abstract syntax tree, or Reader. The administrator API also provides methods
to register and unregister rule execution sets. Only registered rule execution sets are accessible through the runtime client API.
Major Rule Engine Vendors:
JBoss Business Process management suite - jBPM
PagaRULES - PegaRULES Process Commander
Following code illustrates how a Java application can use this API to integrate with any JSR-94 implemented Rule Engine
import javax.rules.RuleServiceProviderManager;
import javax.rules.StatefulRuleSession;
import javax.rules.StatelessRuleSession;
import javax.rules.admin.RuleAdministrator;
import javax.rules.admin.RuleExecutionSet;
// external imports
import org.jcp.jsr94.tck.model.Customer;
import org.jcp.jsr94.tck.model.Invoice;
/**
* This class implement a simple example using a rule execution set
* from the Test Compatibility Kit.
*
* See for the TCK for more information on the object model and the
* rule execution set.
*
* This example requires the following jar file to be present on your
* classpath:
* jsr94.jar
* jsr94-ri.jar
* jsr94-tck.jar
* xerces.jar
* jess.jar (The reference implementation)
*
* To run this example execute the following command in the lib
* directory of the jsr94 distribution:
* java -jar jsr94-example.jar
*/
public class Example
{
// The rule service provider uri as defined by the reference
// implementation.
private static final String RULE_SERVICE_PROVIDER = "org.jcp.jsr94.jess";
/**
* Main entry point.
*/
public static void main( String[] args )
{
try
{
// Load the rule service provider of the reference
// implementation.
// Loading this class will automatically register this
// provider with the provider manager.
Class.forName( "org.jcp.jsr94.jess.RuleServiceProviderImpl" );
// Get the rule service provider from the provider manager.
RuleServiceProvider serviceProvider = RuleServiceProviderManager.getRuleServiceProvider( RULE_SERVICE_PROVIDER );
// get the RuleAdministrator
RuleAdministrator ruleAdministrator = serviceProvider.getRuleAdministrator();
System.out.println("\nAdministration API\n");
System.out.println( "Acquired RuleAdministrator: " +
ruleAdministrator );
// get an input stream to a test XML ruleset
// This rule execution set is part of the TCK.
InputStream inStream = org.jcp.jsr94.tck.model.Customer.class.getResourceAsStream( "/org/jcp/jsr94/tck/tck_res_1.xml" );
System.out.println("Acquired InputStream to RI tck_res_1.xml: " +
inStream );
// parse the ruleset from the XML document
RuleExecutionSet res1 = ruleAdministrator.getLocalRuleExecutionSetProvider( null ).createRuleExecutionSet( inStream, null );
inStream.close();
System.out.println( "Loaded RuleExecutionSet: " + res1);
// register the RuleExecutionSet
String uri = res1.getName();
ruleAdministrator.registerRuleExecutionSet(uri, res1, null );
System.out.println( "Bound RuleExecutionSet to URI: " + uri);
// Get a RuleRuntime and invoke the rule engine.
System.out.println( "\nRuntime API\n" );
RuleRuntime ruleRuntime = serviceProvider.getRuleRuntime();
System.out.println( "Acquired RuleRuntime: " + ruleRuntime );
// create a StatelessRuleSession
StatelessRuleSession statelessRuleSession =
(StatelessRuleSession) ruleRuntime.createRuleSession(uri,
new HashMap(), RuleRuntime.STATELESS_SESSION_TYPE);
System.out.println( "Got Stateless Rule Session: " +
statelessRuleSession );
// call executeRules with some input objects
// Create a Customer as specified by the TCK documentation.
Customer inputCustomer = new Customer("test");
inputCustomer.setCreditLimit(5000);
// Create an Invoice as specified by the TCK documentation.
Invoice inputInvoice = new Invoice("Invoice 1");
inputInvoice.setAmount(2000);
// Create a input list.
List input = new ArrayList();
input.add(inputCustomer);
input.add(inputInvoice);
// Print the input.
System.out.println("Calling rule session with the following data");
System.out.println("Customer credit limit input: " +
inputCustomer.getCreditLimit());
System.out.println(inputInvoice.getDescription() +
" amount: " + inputInvoice.getAmount() +
" status: " + inputInvoice.getStatus());
// Execute the rules without a filter.
List results = statelessRuleSession.executeRules(input);
System.out.println( "Called executeRules on Stateless Rule Session: " + statelessRuleSession );
System.out.println( "Result of calling executeRules: " +
results.size() + " results." );
// Loop over the results.
Iterator itr = results.iterator();
while(itr.hasNext()) {
Object obj = itr.next();
if (obj instanceof Customer)
System.out.println("Customer credit limit result: " +
((Customer) obj).getCreditLimit());
if (obj instanceof Invoice)
System.out.println(((Invoice) obj).getDescription() +
" amount: " + ((Invoice) obj).getAmount() +
" status: " + ((Invoice) obj).getStatus());
}
// Release the session.
statelessRuleSession.release();
System.out.println( "Released Stateless Rule Session." );
System.out.println();
// create a StatefulRuleSession
StatefulRuleSession statefulRuleSession =
(StatefulRuleSession) ruleRuntime.createRuleSession( uri,
new HashMap(),
RuleRuntime.STATEFUL_SESSION_TYPE );
System.out.println( "Got Stateful Rule Session: " + statefulRuleSession );
// Add another Invoice.
Invoice inputInvoice2 = new Invoice("Invoice 2");
inputInvoice2.setAmount(1750);
input.add(inputInvoice2);
System.out.println("Calling rule session with the following data");
System.out.println("Customer credit limit input: " +
inputCustomer.getCreditLimit());
System.out.println(inputInvoice.getDescription() +
" amount: " + inputInvoice.getAmount() +
" status: " + inputInvoice.getStatus());
System.out.println(inputInvoice2.getDescription() +
" amount: " + inputInvoice2.getAmount() +
" status: " + inputInvoice2.getStatus());
// add an Object to the statefulRuleSession
statefulRuleSession.addObjects( input );
System.out.println( "Called addObject on Stateful Rule Session: "
+ statefulRuleSession );
statefulRuleSession.executeRules();
System.out.println( "Called executeRules" );
// extract the Objects from the statefulRuleSession
results = statefulRuleSession.getObjects();
System.out.println( "Result of calling getObjects: " +
results.size() + " results." );
// Loop over the results.
itr = results.iterator();
while(itr.hasNext()) {
Object obj = itr.next();
if (obj instanceof Customer)
System.out.println("Customer credit limit result: " +
((Customer) obj).getCreditLimit());
if (obj instanceof Invoice)
System.out.println(((Invoice) obj).getDescription() +
" amount: " + ((Invoice) obj).getAmount() +
" status: " + ((Invoice) obj).getStatus());
}
// release the statefulRuleSession
statefulRuleSession.release();
System.out.println( "Released Stateful Rule Session." );
System.out.println();
}
catch (NoClassDefFoundError e)
{
if (e.getMessage().indexOf("JessException") != -1)
{
System.err.println("Error: The reference implementation Jess could not be found.");
}
else
{
System.err.println("Error: " + e.getMessage());
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
More info:
http://jcp.org/aboutJava/communityprocess/first/jsr094/index.html
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