自从JBPM 4发布以后，很多人谈到jBPM和它的命运。两个jBPM项目的大牛Tom Baeyens和Joram Barrez离开了jBPM项目，并开始了一个命名为“Activiti”的项目，该项目由Alfresco公司支持。当前jBPM（4.4）的稳定版本是没有红帽在JBoss SOA平台商业支持，但尽管如此，JBPM5是BPM解决方案的一个非常好的选择。它也集成了Drools，所以人们也可以轻松整合BPM规则系统，此外，JBPM5支持BPMN2.0。
这篇文章，介绍了一些简单的步骤来开启JBPM 5.0，非常简单的低层次的例子来理解JBPM API。该示例包括所示代码的流程定义的执行。
KnowledgeBase:
The jBPM API allows you to first create a knowledge base. The Knowledge Base is a repository of all the application’s knowledge definitions. It may contain rules, processes, functions etc. The Knowledge Base itself does not contain instance data, known as facts; instead, sessions are created from the Knowledge Base into which data can be inserted and where process instances may be started. The following code snippet shows how to create a knowledge base consisting of only one process definition.
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource("TestProcess.bpmn"), ResourceType.BPMN2); KnowledgeBase kbase = kbuilder.newKnowledgeBase();Knowledge Session:
Next step is to start a session to interact with created knowledge base. The following code snippet shows how easy it is to create a session based on the earlier created knowledge base, and to start a process.
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); ProcessInstance processInstance = ksession.startProcess("first_test");Events:
JBPM API allows you to listens to some events during process execution to interact with JBPM runtime. A ProcessEventListener can be used to listen to process-related events, like starting or completing a process, entering and leaving a node, etc. You can set your listener class using following line of code.
ksession.addEventListener(new TestEventListener());Input Parameters:
You can also provide some input parameters to help you executing your business logic meanwhile the process is executing. Following code sample shows how to provide input parameters to a process execution.
Map<String, Object> inputParams = new HashMap<String, Object>(); inputParams.put("name", "i am an input parameter."); ProcessInstance processInstance = ksession.startProcess("first_test", inputParams);You can access this parameter during process execution in your event listener implementation.
public class TestEventListener implements ProcessEventListener { @Override public void beforeNodeTriggered(ProcessNodeTriggeredEvent event) { System.out.println("Before Node triggered event received for node: "+ event.getNodeInstance().getNodeName()); Object obj = event.getNodeInstance().getVariable("name"); System.out.println("Input Parameter of ProcessInstance: "+obj.toString()); } }Now, let’s put up all together in a test class. Followings are libraries I have includes in my eclipse workspace. You can download them from here.
BPMN 2.0 Process Definition
Following is a sample process definition that I have used in my test class. It contains three nodes: start, script task and end node. ScriptTask simply prints something when it executes. The id attribute in Process tag is used in starting workflow from session.
<definitions id="Definition" targetNamespace="http://www.jboss.org/drools" typeLanguage="http://www.java.com/javaTypes" expressionLanguage="http://www.mvel.org/2.0" xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.omg.org/spec/BPMN/20100524/MODEL BPMN20.xsd" xmlns:g="http://www.jboss.org/drools/flow/gpd" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" xmlns:tns="http://www.jboss.org/drools"> <process processType="Private" isExecutable="true" id="first_test" name="Hello"> <!-- nodes --> <startEvent id="_1" name="Start" > </startEvent> <scriptTask id="_2" name="Hello" > <script>System.out.println("This is my first test process.");</script> </scriptTask> <endEvent id="_3" name="End" > <terminateEventDefinition/> </endEvent> <!-- connections --> <sequenceFlow id="_1-_2" sourceRef="_1" targetRef="_2" /> <sequenceFlow id="_2-_3" sourceRef="_2" targetRef="_3" /> </process> </definitions>TestEventListener.java
import org.drools.event.process.ProcessCompletedEvent; import org.drools.event.process.ProcessEventListener; import org.drools.event.process.ProcessNodeLeftEvent; import org.drools.event.process.ProcessNodeTriggeredEvent; import org.drools.event.process.ProcessStartedEvent; import org.drools.event.process.ProcessVariableChangedEvent; public class TestEventListener implements ProcessEventListener { @Override public void beforeNodeTriggered(ProcessNodeTriggeredEvent event) { System.out.println("Before Node triggered. "+event.getNodeInstance().getNodeName()); Object obj = event.getNodeInstance().getVariable("name"); System.out.println("Input Parameter of ProcessInstance: "+obj.toString()); } @Override public void afterNodeLeft(ProcessNodeLeftEvent arg0) {} @Override public void afterNodeTriggered(ProcessNodeTriggeredEvent arg0) {} @Override public void afterProcessCompleted(ProcessCompletedEvent arg0) {} @Override public void afterProcessStarted(ProcessStartedEvent arg0) {} @Override public void afterVariableChanged(ProcessVariableChangedEvent arg0) {} @Override public void beforeNodeLeft(ProcessNodeLeftEvent arg0) {} @Override public void beforeProcessCompleted(ProcessCompletedEvent arg0) {} @Override public void beforeProcessStarted(ProcessStartedEvent arg0) {} @Override public void beforeVariableChanged(ProcessVariableChangedEvent arg0) {} }FirstTest.java
import java.util.HashMap; import java.util.Map; import org.drools.KnowledgeBase; import org.drools.builder.KnowledgeBuilder; import org.drools.builder.KnowledgeBuilderFactory; import org.drools.builder.ResourceType; import org.drools.io.ResourceFactory; import org.drools.runtime.StatefulKnowledgeSession; import org.drools.runtime.process.ProcessInstance; public class FirstTest { public static void main(String[] args) { KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource("conf/TestProcess.bpmn"), ResourceType.BPMN2); KnowledgeBase kbase = kbuilder.newKnowledgeBase(); StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); ksession.addEventListener(new TestEventListener()); Map<String, Object> inputParams = new HashMap<String, Object>(); inputParams.put("name", "i am an input parameter."); ProcessInstance processInstance = ksession.startProcess("first_test", inputParams); } }