2:17 p.m.
Hi Pritam,
As you mentioned, KA loads, caches and reload kbases. When the KA process a
change-set, adds a Listener to every resource so it can detect when they are
modified. In order to detect these modifications, two services should be
running: *ResourceChangeScannerService* and *ResourceChangeNotifierService *(as
you are already doing).
Listeners are only set for those resources of a change-set, if the initial
kbase contained preloaded rules, their resources are not monitored. What I
recommend to use change-sets. It seams that your error is in the change-set
structure. You must pass a xml definition of a change-set to
KA#applyChangeSet() and not a path to a file. Here is an example of a well
formed change-set that can be passed to applyChangeSet():
*String xml = "";*
* xml += "<change-set xmlns='http://drools.org/drools-5.0/change-set
'";*
* xml += "
xmlns:xs='http://www.w3.org/2001/XMLSchema-instance'";*
* xml += " xs:schemaLocation='
http://drools.org/drools-5.0/change-set drools-change-set-5.0.xsd' >";*
* xml += " <add> ";*
* xml += " <resource
source='http://localhost:9000/rule1.drl'
type='DRL' />";*
* xml += " <resource
source='http://localhost:9000/rule2.drl'
type='DRL' />";*
* xml += " </add> ";*
* xml += "</change-set>";*
This is a change-set that contains 2 resources. They are accessed using
http, but you can use *file://* if they are local.
Best,
On Thu, Jan 14, 2010 at 10:17 PM, Pritam <infinity2heaven(a)gmail.com> wrote:
Before I ask the problem, here's the design I currently have:
Our "site" (webapp) has 100 pages. While rendering each page, the rule
engine is called for filtering the page contents. We have 100 drl files
(corresponding to each page). Since creating of a KnowledgeBase is
expensive, I'm using a KnowledgeAgent.getKnowledeBase() since the javadocs
mentions it as "it loads, caches, reloads knowledgeBase."
However after using the sample code given, a change in the rule file is not
reloading the knowledgeBase automatically. Note that I cache the
knowledgeAgent since I need one agent per knowledge base (is there a better
way to manage multiple drl files in one knowledge base and agent?)
Is something wrong with the below code?
// ruleFile is a complete file path on server
public static KnowledgeBase createKnowledgeBaseFromAgent(String ruleFile)
throws DroolsParserException, IOException {
ResourceChangeScannerConfiguration sconf = ResourceFactory
.getResourceChangeScannerService()
.newResourceChangeScannerConfiguration();
// static map of knowledgeAgents
if (knowledgeAgents.containsKey(ruleFile)) {
return
((KnowledgeAgent)knowledgeAgents.get(ruleFile)).getKnowledgeBase();
}
sconf.setProperty("drools.resource.scanner.interval", "5");
ResourceFactory.getResourceChangeScannerService().configure(sconf);
KnowledgeBase knowledgeBase = createKnowledgeBase(ruleFile);
ResourceFactory.getResourceChangeScannerService().start();
ResourceFactory.getResourceChangeNotifierService().start();
KnowledgeAgentConfiguration conf =
KnowledgeAgentFactory.newKnowledgeAgentConfiguration();
conf.setProperty("drools.agent.scanDirectories", "true");
final KnowledgeAgent agent =
KnowledgeAgentFactory.newKnowledgeAgent(
"my agent", knowledgeBase, conf);
// agent.applyChangeSet(ResourceFactory.newFileResource(ruleFile));
setKnowledgeAgent(ruleFile, agent);
return agent.getKnowledgeBase();
}
public static KnowledgeBase createKnowledgeBase(
KnowledgeBaseConfiguration config,
KnowledgeBuilderConfiguration knowledgeBuilderConfig,
String ruleFile) throws DroolsParserException, IOException {
// else, create a knowledgeBase
KnowledgeBuilder knowledgeBuilder =
KnowledgeBuilderFactory.newKnowledgeBuilder(knowledgeBuilderConfig);
knowledgeBuilder.add(ResourceFactory.newFileResource(ruleFile),
ResourceType.DRL);
if (knowledgeBuilder.hasErrors()) {
throw new RuntimeException(knowledgeBuilder.getErrors().toString());
}
KnowledgeBase knowledgeBase =
KnowledgeBaseFactory.newKnowledgeBase(config);
knowledgeBase.addKnowledgePackages(knowledgeBuilder.getKnowledgePackages());
return knowledgeBase;
}
I commented out
agent.applyChangeSet(ResourceFactory.newFileResource(ruleFile));
since I get a NPE
java.lang.NullPointerException
at
org.drools.agent.impl.KnowledgeAgentImpl.processChangeSet(KnowledgeAgentImpl.java:135)
Pl suggest
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