工作流系列(5.1)-Activiti流程文件解析功能架构设计

对于解析流程文件，Activiti使用的是流模式，在5.12.1之前使用的是推模式（SAX），而在此之后使用的拉模式（STAX）。

配置文件

之前也讲到，流程文件是通过XML文件配置的，如下所示：

<definitions id="definitions"
             targetNamespace="http://activiti.org/bpmn20"
             xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xmlns:activiti="http://activiti.org/bpmn">

  <process id="vacationRequest" name="Vacation request">

    <startEvent id="request" activiti:initiator="employeeName">
      <extensionElements>
        <activiti:formProperty id="numberOfDays" name="Number of days" type="long" value="1" required="true"/>
        <activiti:formProperty id="startDate" name="First day of holiday (dd-MM-yyy)" datePattern="dd-MM-yyyy hh:mm" type="date" required="true" />
        <activiti:formProperty id="vacationMotivation" name="Motivation" type="string" />
      extensionElements>
    startEvent>
    <sequenceFlow id="flow1" sourceRef="request" targetRef="handleRequest" />

    <userTask id="handleRequest" name="Handle vacation request" >
      <documentation>
        ${employeeName} would like to take ${numberOfDays} day(s) of vacation (Motivation: ${vacationMotivation}).
      documentation>
      <extensionElements>
         <activiti:formProperty id="vacationApproved" name="Do you approve this vacation" type="enum" required="true">
          <activiti:value id="true" name="Approve" />
          <activiti:value id="false" name="Reject" />
        activiti:formProperty>
        <activiti:formProperty id="managerMotivation" name="Motivation" type="string" />
      extensionElements>
      <potentialOwner>
        <resourceAssignmentExpression>
          <formalExpression>managementformalExpression>
        resourceAssignmentExpression>
      potentialOwner>
    userTask>
    <sequenceFlow id="flow2" sourceRef="handleRequest" targetRef="requestApprovedDecision" />

    <exclusiveGateway id="requestApprovedDecision" name="Request approved?" />
    <sequenceFlow id="flow3" sourceRef="requestApprovedDecision" targetRef="sendApprovalMail">
      <conditionExpression xsi:type="tFormalExpression">${vacationApproved == 'true'}conditionExpression>
    sequenceFlow>

    <task id="sendApprovalMail" name="Send confirmation e-mail" />
    <sequenceFlow id="flow4" sourceRef="sendApprovalMail" targetRef="theEnd1" />
    <endEvent id="theEnd1" />

    <sequenceFlow id="flow5" sourceRef="requestApprovedDecision" targetRef="adjustVacationRequestTask">
      <conditionExpression xsi:type="tFormalExpression">${vacationApproved == 'false'}conditionExpression>
    sequenceFlow>

    <userTask id="adjustVacationRequestTask" name="Adjust vacation request">
      <documentation>
        Your manager has disapproved your vacation request for ${numberOfDays} days.
        Reason: ${managerMotivation}
      documentation>
      <extensionElements>
        <activiti:formProperty id="numberOfDays" name="Number of days" value="${numberOfDays}" type="long" required="true"/>
        <activiti:formProperty id="startDate" name="First day of holiday (dd-MM-yyy)" value="${startDate}" datePattern="dd-MM-yyyy hh:mm" type="date" required="true" />
        <activiti:formProperty id="vacationMotivation" name="Motivation" value="${vacationMotivation}" type="string" />
        <activiti:formProperty id="resendRequest" name="Resend vacation request to manager?" type="enum" required="true">
          <activiti:value id="true" name="Yes" />
          <activiti:value id="false" name="No" />
        activiti:formProperty>
      extensionElements>
      <humanPerformer>
        <resourceAssignmentExpression>
          <formalExpression>${employeeName}formalExpression>
        resourceAssignmentExpression>
      humanPerformer>
    userTask>
    <sequenceFlow id="flow6" sourceRef="adjustVacationRequestTask" targetRef="resendRequestDecision" />

    <exclusiveGateway id="resendRequestDecision" name="Resend request?" />
    <sequenceFlow id="flow7" sourceRef="resendRequestDecision" targetRef="handleRequest">
      <conditionExpression xsi:type="tFormalExpression">${resendRequest == 'true'}conditionExpression>
    sequenceFlow>

     <sequenceFlow id="flow8" sourceRef="resendRequestDecision" targetRef="theEnd2">
      <conditionExpression xsi:type="tFormalExpression">${resendRequest == 'false'}conditionExpression>
    sequenceFlow>
    <endEvent id="theEnd2" />

  process>

definitions>

这只一个流程文件，摘自Activiti用户手册

BPMN2.0元素与Activiti的支持

对于BPMN元素的介绍，可以看 工作流系列(2)-BPMN简介。

Activiti对于BPMN元素的支持，只列出最基本的元素

事件(Event)

简单的介绍开始结束事件，其他的比如边界事件等暂不介绍

BPMN元素	Activiti 类	配置文件表示
开始事件	StartEvent
结束事件	EndEvent

活动(Activity)

活动包含任务、子流程

任务(Task)

只介绍常用的，当然还有其他的比如：业务规则任务、接受任务等

BPMN元素	Activiti 类	配置文件表示
用户任务	UserTask
服务任务	ServiceTask
手工任务	ManualTask

还有比如：脚本任务 ScriptTask

<scriptTask id="theScriptTask" name="Execute script" scriptFormat="groovy">
  <script>
    sum = 0
    for ( i in inputArray ) {
      sum += i
    }
  script>
scriptTask>

子流程

• 嵌入子流程 subProcess

<subProcess id="subProcess">
  <startEvent id="subProcessStart" />
  ... other Sub-Process elements ...
  <endEvent id="subProcessEnd" />
 subProcess>

• 调用子流程 callActivity

<callActivity id="callCheckCreditProcess" name="Check credit" calledElement="checkCreditProcess" />

网关

BPMN元素	Activiti 类	配置文件表示
并行网关	ParallelGateway
排他网关	ExclusiveGateway
包容网关	InclusiveGateway

链接对象

BPMN元素	Activiti 类	配置文件表示
顺序流	SequenceFlow

在顺序流中可以增加条件，比如

<sequenceFlow id="flow3" sourceRef="requestApprovedDecision" targetRef="sendApprovalMail">
      <conditionExpression xsi:type="tFormalExpression">${vacationApproved == 'true'}conditionExpression>
    sequenceFlow>

解析架构设计

Activiti的解析工作，就是将配置文件中的元素转换为对应的Java类，如果说Java类在对顶层，则配置文件就位于最底层，而在这两者中间就是转换器与解析器。
首先对于每一个元素都有公共的属性，比如id、name等，对于这些公共属性，我们可以将其提取到公共的方法中进行解析。但是每个元素都有自己独特的属性，所以Activiti为每一个元素都定义了解析器或转换器，以便当每个元素增添属性时，只需要修改特定的解析器就可以实现。

元素与转换

BpmnXMLConverter是转换的入口，它读取配置文件并进行循环解析，通过注册不同的转换器来转换不同的元素，而在转化器中通过自己解析或调用解析器解析元素，并最终构建BpmnModel对象。
很多元素都具有相同的构造，所以拥有一个公共的解析方式；拥有公共的扩展属性（ExtensionAttribute），这些使用同一个解析器循环处理。

转化器

元素	Java类	转换器	备注
endEvent	EndEvent	EndEventXMLConverter
startEvent	StartEvent	StartEventXMLConverter
businessRuleTask	BusinessRuleTask	BusinessRuleTaskXMLConverter
manualTask	ManualTask	ManualTaskXMLConverter
receiveTask	ReceiveTask	ReceiveTaskXMLConverter
scriptTask	ScriptTask	ScriptTaskXMLConverter
serviceTask	ServiceTask	ServiceTaskXMLConverter
sendTask	SendTask	SendTaskXMLConverter
userTask	UserTask	UserTaskXMLConverter
task	Task	TaskXMLConverter
callActivity	CallActivity	CallActivityXMLConverter
eventGateway	EventGateway	EventGatewayXMLConverter
exclusiveGateway	ExclusiveGateway	ExclusiveGatewayXMLConverter
inclusiveGateway	InclusiveGateway	InclusiveGatewayXMLConverter
parallelGateway	ParallelGateway	ParallelGatewayXMLConverter
complexGateway	ComplexGateway	ComplexGatewayXMLConverter
sequenceFlow	SequenceFlow	SequenceFlowXMLConverter
catchEvent	CatchEvent	CatchEventXMLConverter
throwEvent	ThrowEvent	ThrowEventXMLConverter
boundaryEvent	BoundaryEvent	BoundaryEventXMLConverter
textAnnotation	TextAnnotation	TextAnnotationXMLConverter
association	Association	AssociationXMLConverter
dataStoreReference	DataStoreReference	DataStoreReferenceXMLConverter
valuedDataObject	ValuedDataObject	ValuedDataObjectXMLConverter
alfrescoStartEvent	AlfrescoStartEvent	AlfrescoStartEventXMLConverter
alfrescoUserTask	AlfrescoUserTask	AlfrescoUserTaskXMLConverter

解析器

解析器所在包是org.activiti.bpmn.converter.child和org.activiti.bpmn.converter.parse

元素	Java类	解析器	备注
process	Process	ProcessParse
subProcess	SubProcess	SubProcessParser
bpmndi:BPMNEdge	GraphicInfo	BpmnEdgeParser	解析的是顺序流等线段图形位置等信息
bpmndi:BPMNShape	GraphicInfo	BpmnShapeParser	解析的是任务等非线段图形位置、宽高等信息
lane	Lane	LaneParser
pool	Pool	ParticipantParser
messageFlow	MessageFlow	MessageFlowParser
activiti:executionListener	ExecutionListener	ExecutionListenerParser	执行监听器
activiti:taskListener	ActivitiListener	TaskListenerParser	任务监听器解析
multiInstanceLoopCharacteristics	MultiInstanceLoopCharacteristics	MultiInstanceParser	解析包括loopCardinality、isSequential、completionCondition等信息