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JBoss BRMS - 呼叫Rule 與 BPMN 的API

學 BRMS 呼叫 Rules 與 BPMN 的 API 真的很划算,因為學一套 API 在 Rules 與 BPMN 都在用。而且概念還滿簡單的。

最主要就是這四個Class, 會使用他們基本上大概就可以操作JBoss Rules (Drools) 與 jBPM了!


  • KnowledgeBuilder
  • KnowledgeBase
  • StatefulKnowledgeSession
  • StatelessKnowledgeSession

KnowledgeBuilder

望文生義,這個Class 就是專門把各地的的資源,如 Drl 的檔案,jBPM 的 BPMN, 整包的binary package讀取進來,透過KnowledgeBuilderFactory 取得Builder。

如何建立一個Builder 並載入需要的Rule與資源?

A. 載入Drools ,
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();kbuilder.add( ResourceFactory.newUrlResource( "file://myrules.drl" ),ResourceType.DRL);
B.載入 Excel 的 Decision Table,

DecisionTableConfiguration dtconf = KnowledgeBuilderFactory.newDecisionTableConfiguration();
dtconf.setInputType( DecisionTableInputType.XLS );
dtconf.setWorksheetName( "Tables_2" );
kbuilder.add( ResourceFactory.newUrlResource( "file://IntegrationExampleTest.xls" ),ResourceType.DTABLE,dtconf );


C.載入 jBPM 的BPMN2.0檔案

kbuilder.add( ResourceFactory.newUrlResource( "file://myProcess.bpmn2" ),
ResourceType.BPMN2 );


D.從遠端的BRMS管理網站讀取打包好的package檔案(包含了以上三種)

String url = "http://IP:PORT/jboss-brms/rest/packages/xx.yy.aa/binary"; UrlResource resource = (UrlResource) ResourceFactory.newUrlResource(url); resource.setBasicAuthentication("enabled"); resource.setUsername("ID"); resource.setPassword("PWD"); kbuilder.add(resource, ResourceType.PKG);
E. 除了以上寫在程式內的方式外,還可以獨立用XML定義,可以新增一個sampleRule.xml <change-set xmlns='http://drools.org/drools-5.0/change-set'xmlns:xs='http://www.w3.org/2001/XMLSchema-instance'xs:schemaLocation='http://drools.org/drools-5.0/change-set.xsd http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-api/src/main/resources/change-set-1.0.0.xsd' >   <add>   <resource source='http:org/domain/myrules.drl' type='DRL' />   <resource source='classpath:data/IntegrationExampleTest.xls' type="DTABLE"> <decisiontable-conf input-type="XLS" worksheet-name="Tables_2" />   </resource>   </add> </change-set> kbuilder.add( ResourceFactory.newUrlResource( "sampleRule.xml" ), ResourceType.CHANGE_SET );
讀取後,最好保持好習慣確認一下有沒有錯誤,
if ( kbuilder.hasErrors() ) {
log.exception( kbuilder.getErrors().toString());
}

當Builder把資源讀取完之後,就會把編譯後可以執行的 binary放置的地方拉。所以如果你想要更新引擎上面執行的Rules還是流程,就要重新載入這個部分!因為要將所有的Rule 編譯,所以會滿耗費資源的,因此我建議大家啦~ 如果可以就把這個KnowledgeBase 暫存起來在系統裡,反覆地使用會比較好!

KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();kbase.addKnowledgePackages( kbuilder.getKnowledgePackages() );

這個Session 會保持一連串呼叫的狀態。因為他會保留context中的資訊,可以再上一個執行結果之下再做更多的計算跟使用。以jBPM來說,大部份都是使用這種session.
呼叫之後就可以直接insert Facts ,insert的 Fact都會被留在working memory裡面,狀態也會保存。直到session 結束為止。

StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();

for( Object fact : facts ) {
     ksession.insert( fact );
}

ksession.fireAllRules();
ksession.dispose();


StatelessKnowledgeSession

這個Session 並不會保持狀態,也就是說,上一次的變動與下一次的變動是獨立的。因為是這種特性,它可以重複的被一直使用。所以適合在需要一直重複執行然後取得一個結果的規則。
執行的方式,就是呼叫execute, 直接把物件帶入,

StatelessKnowledgeSession ksession = kbase.newStatelessKnowledgeSession();
ksession.execute( collection );

如果想要同時輸入不同的物件,就需要借助 CommandFactory 把物件存放在一個 collection裡面執行啦。

List cmds = new ArrayList();
cmds.add( CommandFactory.newSetGlobal( "list1", new ArrayList() ) );
cmds.add( CommandFactory.newInsert( new Person( "jon", 102 ) ) );

StatelessKnowledgeSession ksession = kbase.newStatelessKnowledgeSession(); 
ksession.execute( CommandFactory.newBatchExecution( cmds ) );

以上。





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