Activiti 流程启动及节点流转源码分析

作者：jiankunking 出处：http://blog.csdn.net/jiankunking

本文主要是以activiti-study中的xiaomage.xml流程图为例进行跟踪分析

具体的流程图如下：



流程图对应的XML文件如下：

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:activiti="http://activiti.org/bpmn" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:omgdc="http://www.omg.org/spec/DD/20100524/DC" xmlns:omgdi="http://www.omg.org/spec/DD/20100524/DI" typeLanguage="http://www.w3.org/2001/XMLSchema" expressionLanguage="http://www.w3.org/1999/XPath" targetNamespace="http://www.activiti.org/test">
<process id="MyProcess" name="MyProcess">
<documentation>Place documentation for the 'MyProcess' process here.</documentation>
<startEvent id="startevent1" name="Start"/>
<userTask id="sss" name="ddd" activiti:assignee="fq"/>
<sequenceFlow id="flow1" name="" sourceRef="startevent1" targetRef="sss"/>
<endEvent id="endevent1" name="End"/>
<sequenceFlow id="flow2" name="" sourceRef="sss" targetRef="endevent1"/>
</process>
<bpmndi:BPMNDiagram id="BPMNDiagram_MyProcess">
<bpmndi:BPMNPlane bpmnElement="MyProcess" id="BPMNPlane_MyProcess">
<bpmndi:BPMNShape bpmnElement="startevent1" id="BPMNShape_startevent1">
<omgdc:Bounds height="35" width="35" x="340" y="150"/>
</bpmndi:BPMNShape>
<bpmndi:BPMNShape bpmnElement="sss" id="BPMNShape_sss">
<omgdc:Bounds height="55" width="105" x="305" y="250"/>
</bpmndi:BPMNShape>
<bpmndi:BPMNShape bpmnElement="endevent1" id="BPMNShape_endevent1">
<omgdc:Bounds height="35" width="35" x="340" y="370"/>
</bpmndi:BPMNShape>
<bpmndi:BPMNEdge bpmnElement="flow1" id="BPMNEdge_flow1">
<omgdi:waypoint x="357" y="185"/>
<omgdi:waypoint x="357" y="250"/>
</bpmndi:BPMNEdge>
<bpmndi:BPMNEdge bpmnElement="flow2" id="BPMNEdge_flow2">
<omgdi:waypoint x="357" y="305"/>
<omgdi:waypoint x="357" y="370"/>
</bpmndi:BPMNEdge>
</bpmndi:BPMNPlane>
</bpmndi:BPMNDiagram>
</definitions>

流程实例创建过程如下（下图转载自：activiti 源码笔记之startProcess）：



流程启动跟踪分析：

图一：



图二：



图三：



图四：



以上主要是跟踪分析了，三个节点之间的流转情况。

在流转的时候需要注意以下两个接口：

原子操作（AtomicOperation）接口：

public interface AtomicOperation {

AtomicOperation PROCESS_START = new AtomicOperationProcessStart();
AtomicOperation PROCESS_START_INITIAL = new AtomicOperationProcessStartInitial();
AtomicOperation PROCESS_END = new AtomicOperationProcessEnd();
AtomicOperation ACTIVITY_START = new AtomicOperationActivityStart();
AtomicOperation ACTIVITY_EXECUTE = new AtomicOperationActivityExecute();
AtomicOperation ACTIVITY_END = new AtomicOperationActivityEnd();
AtomicOperation TRANSITION_NOTIFY_LISTENER_END = new AtomicOperationTransitionNotifyListenerEnd();
AtomicOperation TRANSITION_DESTROY_SCOPE = new AtomicOperationTransitionDestroyScope();
AtomicOperation TRANSITION_NOTIFY_LISTENER_TAKE = new AtomicOperationTransitionNotifyListenerTake();
AtomicOperation TRANSITION_CREATE_SCOPE = new AtomicOperationTransitionCreateScope();
AtomicOperation TRANSITION_NOTIFY_LISTENER_START = new AtomicOperationTransitionNotifyListenerStart();

AtomicOperation DELETE_CASCADE = new AtomicOperationDeleteCascade();
AtomicOperation DELETE_CASCADE_FIRE_ACTIVITY_END = new AtomicOperationDeleteCascadeFireActivityEnd();

void execute(InterpretableExecution execution);

boolean isAsync(InterpretableExecution execution);
}

注意：

void execute(InterpretableExecution execution);

InterpretableExecution接口：

public interface InterpretableExecution extends ActivityExecution, ExecutionListenerExecution, PvmProcessInstance {

void take(PvmTransition transition);

void take(PvmTransition transition, boolean fireActivityCompletedEvent);

void setEventName(String eventName);

void setEventSource(PvmProcessElement element);

Integer getExecutionListenerIndex();
void setExecutionListenerIndex(Integer executionListenerIndex);

ProcessDefinitionImpl getProcessDefinition();

void setActivity(ActivityImpl activity);

void performOperation(AtomicOperation etomicOperation);

boolean isScope();

void destroy();

void remove();

InterpretableExecution getReplacedBy();
void setReplacedBy(InterpretableExecution replacedBy);

InterpretableExecution getSubProcessInstance();
void setSubProcessInstance(InterpretableExecution subProcessInstance);

InterpretableExecution getSuperExecution();

void deleteCascade(String deleteReason);

boolean isDeleteRoot();

TransitionImpl getTransition();
void setTransition(TransitionImpl object);

void initialize();

void setParent(InterpretableExecution parent);

void setProcessDefinition(ProcessDefinitionImpl processDefinitionImpl);

void setProcessInstance(InterpretableExecution processInstance);

boolean isEventScope();

void setEventScope(boolean isEventScope);

StartingExecution getStartingExecution();

void disposeStartingExecution();
}

注意：

void performOperation(AtomicOperation etomicOperation);

单独摘出来的两个方法是图一中：



上下文、原子操作、执行器实体三者相互调用的关键。

上图的具体调用情况如下：

ExecutionEntity类中的：

public void performOperation(AtomicOperation executionOperation) {
if (executionOperation.isAsync(this)) {
scheduleAtomicOperationAsync(executionOperation);
} else {
performOperationSync(executionOperation);
}
}

protected void performOperationSync(AtomicOperation executionOperation) {
Context
.getCommandContext()
.performOperation(executionOperation, this);
}

performOperation函数中调用上下文CommandContext类中的：

public void performOperation(AtomicOperation executionOperation, InterpretableExecution execution) {
nextOperations.add(executionOperation);
if (nextOperations.size()==1) {
try {
Context.setExecutionContext(execution);
while (!nextOperations.isEmpty()) {
AtomicOperation currentOperation = nextOperations.removeFirst();
if (log.isTraceEnabled()) {
log.trace("AtomicOperation: {} on {}", currentOperation, this);
}
if (execution.getReplacedBy() == null) {
currentOperation.execute(execution);
} else {
currentOperation.execute(execution.getReplacedBy());
}
}
} finally {
Context.removeExecutionContext();
}
}
}

performOperation函数调用原子操作（AtomicOperation）接口中的void execute(InterpretableExecution execution)来处理。

该处的处理分为两种情况：

1、根据AtomicOperation接口标识来继续进行流转

（再次调用ExecutionEntity类中的performOperation(AtomicOperation executionOperation)方法）

比如：

PROCESS_START=》PROCESS_START_INITIAL=》ACTIVITY_EXECUTE。。。。。。

具体可以参考本文图一到图四的代码跟踪中的标识。

2、根据节点上的ActivityBehavior类进行不同的处理



Activiti节点（开始、结束、任务、网关等等）都是Activity类型的，只是其挂的ActivityBehavior不同，通过不同的ActivityBehavior来实现相应的操作。

作者：jiankunking 出处：http://blog.csdn.net/jiankunking