org.drools.agent.KnowledgeAgentFactory Maven / Gradle / Ivy
package org.drools.agent;
import java.util.Properties;
import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseFactory;
import org.drools.ProviderInitializationException;
import org.drools.io.ResourceFactory;
/**
*
* The KnowlegeAgent is created by the KnowlegeAgentFactory. The KnowlegeAgent provides automatic loading, caching and
* re-loading, of resources and is configured from a properties files. The KnowledgeAgent can update or rebuild this KnowlegeBase
* as the resources it uses are changed. The strategy for this is determined by the configuration given to the factory, but it is
* typically pull based using regular polling. We hope to add push based updates and rebuilds in future versions.
*
*
*
* The Following example constructs an agent that will build a new KnowledgeBase from the files specified in the path String.
* It will poll those files every 60 seconds, which is the default when polling is enabled and the service started, to see if they are updated.
* If new files are found it will construct a new KnowledgeBase. If the change set specifies a resource that is a directory it's contents will be scanned for changes too.
*
*
*
* KnowledgeAgent kagent = KnowledgeAgentFactory.newKnowledgeAgent( "MyAgent" );
* kagent.applyChangeSet( ResourceFactory.newUrlResource( url ) );
* KnowledgeBase kbase = kagent.getKnowledgeBase();
*
*
* If you wish to change to change the polling time of the scanner, this can be done with the ResourceChangeScannerService on the ResourceFactory
*
* // Set the interval on the ResourceChangeScannerService if the default of 60s is not desirable.
* ResourceChangeScannerConfiguration sconf = ResourceFactory.getResourceChangeScannerService().newResourceChangeScannerConfiguration();
* sconf.setProperty( "drools.resource.scanner.interval",
* "30" ); // set the disk scanning interval to 30s, default is 60s
* ResourceFactory.getResourceChangeScannerService().configure( sconf );
*
*
* The KnowledgeAgent can accept a configuration that allows for some of the defaults to be changed, see KnowledgeAgentConfiguration for details of
* all the support configuration properties. An example property is "drools.agent.scanDirectories", by default any specified directories are
* scanned for new additions, it is possible to disable this.
*
*
* KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
*
* KnowledgeAgentConfiguration kaconf = KnowledgeAgentFactory.newKnowledgeAgentConfiguration();
* kaconf.setProperty( "drools.agent.scanDirectories",
* "false" ); // we do not want to scan directories, just files
*
* KnowledgeAgent kagent = KnowledgeAgentFactory.newKnowledgeAgent( "test agent", // the name of the agent
* kaconf );
* kagent.applyChangeSet( ResourceFactory.newUrlResource( url ) ); // resource to the change-set xml for the resources to add
*
*
*
* You'll notice the property "drools.agent.newInstance", which defaults to true, currently this cannot be set to false. This property when
* true means the KnowledgeBase will be rebuilt as a new instance when changes are detected and that new instance will be available when
* kagent.getKnowledgeBase() is next called. We hope to add incremental KnowledgeBase support in the future, when a "false" value will be supported
* for this property.
*
*
*
* KnowledgeAgents can take a empty KnowledgeBase or a populated one. If a populated KnowledgeBase is provided, the KnowledgeAgent
* will iterate KnowledgeBase and subscribe to the Resource that it finds. While it is possible for the KnowledgeBuilder to build
* all resources found in a directory, that information is lost by the KnowledgeBuilder so those directories will not be continuously scanned.
* Only directories specified as part of the applyChangeSet(Resource) method are monitored.
*
*
*
* Resource scanning is not on by default, it's a service and must be started, the same is for notification. This can be done via the ResourceFactory.
*
*
*
* ResourceFactory.getResourceChangeNotifierService().start();
* ResourceFactory.getResourceChangeScannerService().start();
*
*
*
* For resources that are "polled" from a remote source (via http or similar) - sometimes you may want a local file based cache,
* in case the remote service is not available for whatever reason.
* To enable this:
* Set the system property: "drools.resource.urlcache" to a directory which can be written to and read from
* as a cache - so remote resources will be cached with last known good copies. This will allow the service to be restarted
* even if the remote source is not available.
* For example -Ddrools.resource.urlcache=/home/rulecaches
*
*
*
* @see org.drools.agent.KnowledgeAgent
* @see org.drools.agent.KnowledgeAgentConfiguration
*
*/
public class KnowledgeAgentFactory {
private static KnowledgeAgentProvider provider;
public static KnowledgeAgentConfiguration newKnowledgeAgentConfiguration() {
return getKnowledgeAgentProvider().newKnowledgeAgentConfiguration();
}
public static KnowledgeAgentConfiguration newKnowledgeAgentConfiguration(Properties properties) {
return getKnowledgeAgentProvider().newKnowledgeAgentConfiguration( properties );
}
public static KnowledgeAgent newKnowledgeAgent(String name) {
return getKnowledgeAgentProvider().newKnowledgeAgent( name,
KnowledgeBaseFactory.newKnowledgeBase() );
}
public static KnowledgeAgent newKnowledgeAgent(String name,
KnowledgeBase kbase) {
return getKnowledgeAgentProvider().newKnowledgeAgent( name,
kbase );
}
public static KnowledgeAgent newKnowledgeAgent(String name,
KnowledgeAgentConfiguration configuration) {
return getKnowledgeAgentProvider().newKnowledgeAgent( name,
KnowledgeBaseFactory.newKnowledgeBase(),
configuration );
}
public static KnowledgeAgent newKnowledgeAgent(String name,
KnowledgeBase kbase,
KnowledgeAgentConfiguration configuration) {
return getKnowledgeAgentProvider().newKnowledgeAgent( name,
kbase,
configuration );
}
private static synchronized void setKnowledgeAgentProvider(KnowledgeAgentProvider provider) {
KnowledgeAgentFactory.provider = provider;
}
private static synchronized KnowledgeAgentProvider getKnowledgeAgentProvider() {
if ( provider == null ) {
loadProvider();
}
return provider;
}
private static void loadProvider() {
try {
// we didn't find anything in properties so lets try and us reflection
Class cls = (Class) Class.forName( "org.drools.agent.impl.KnowledgeAgentProviderImpl" );
setKnowledgeAgentProvider( cls.newInstance() );
} catch ( Exception e ) {
throw new ProviderInitializationException( "Provider org.drools.agent.KnowledgeAgentProvider could not be set." );
}
}
}