一個使用示例，五個操作步驟！從此輕松掌握項目中工作流的開發

建立流程

• 要想操作Activiti引擎,需要通過org.activiti.engine.ProcessEngine執行個體暴露的服務.就可以操作一個org.activiti.engine.ProcessEngine
• 建立一個請假申請的工作業務流程:

釋出流程

• 任何與“靜态”資源有關的資料(比如流程定義)都可以通過RepositoryService通路,從概念上講,所有靜态資料都是Activiti的資源内容
• 在src/test/resources/org/activiti/test目錄下建立一個新的xml檔案 VacationRequest.bpmn20.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<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>management</formalExpression>
        </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>           

• 為了讓Activiti引擎知道這個流程,我們必須先進行[釋出],釋出意味着引擎會把BPMN 2.0 xml解析成可以執行的東西,釋出包中的所有流程定義都會添加到資料庫中.這樣,當引擎重新開機時,它依然可以獲得[已釋出]的流程:

ProcessEngine processEngine = ProcessEngines.getDefaultProcessEngine();
RepositoryService repositoryService = processEngine.getRepositoryService();
repositoryService.createDeployment()
  .addClasspathResource("org/activiti/test/VacationRequest.bpmn20.xml")
  .deploy();

Log.info("Number of process definitions: " + repositoryService.createProcessDefinitionQuery().count());           

啟動一個流程執行個體

• 把流程定義釋出到Activiti引擎後,可以基于它發起新流程執行個體.
• 對每個流程定義,都可以有很多流程執行個體.流程定義是"藍圖",流程執行個體是它的一個運作的執行
• 所有與流程運作狀态相關的東西都可以通過RuntimeService獲得.有很多方法可以啟動一個新流程執行個體.
  • 可以在流程執行個體啟動時添加一些流程變量, 因為第一個使用者任務的表達式需要這些變量.流程變量經常會被用到,因為它們賦予來自同一個流程定義的不同流程執行個體的特别含義
  • 流程變量是區分流程執行個體的關鍵
  • 下面使用定義在流程定義xml 中的key來啟動流程執行個體:

Map<String, Object> variables = new HashMap<String, Object>();
variables.put("employeeName", "Kermit");
variables.put("numberOfDays", new Integer(4));
variables.put("vacationMotivation", "I'm really tired!");

RuntimeService runtimeService = processEngine.getRuntimeService();
ProcessInstance processInstance = runtimeService.startProcessInstanceByKey("vacationRequest", variables);

// Verify that we started a new process instance
Log.info("Number of process instances: " + runtimeService.createProcessInstanceQuery().count());           

完成任務

• 流程啟動後,第一步就是使用者任務.這是必須由系統使用者處理的一個環節.
• 使用者會有一個"任務清單",展示了所有必須由整個使用者處理的任務.下面是對應的查詢:

// Fetch all tasks for the management group
TaskService taskService = processEngine.getTaskService();
List<Task> tasks = taskService.createTaskQuery().taskCandidateGroup("management").list();
for (Task task : tasks) {
  Log.info("Task available: " + task.getName());
}           

• 為了讓流程執行個體繼續運作,我們需要完成整個任務.對Activiti來說,就是需要complete任務:

Task task = tasks.get(0);

Map<String, Object> taskVariables = new HashMap<String, Object>();
taskVariables.put("vacationApproved", "false");
taskVariables.put("managerMotivation", "We have a tight deadline!");
taskService.complete(task.getId(), taskVariables);           

• 然後流程執行個體就會進入到下一個環節
• 下一環節允許員工通過表單調整原始的請假申請.員工可以重新送出請假申請,這會使流程重新進入到第一個任務

挂起或激活一個流程

• 可以挂起一個流程定義,當挂起流程定義時,就不能建立新流程了,會抛出一個異常.可以通過RepositoryService挂起一個流程:

repositoryService.suspendProcessDefinitionByKey("vacationRequest");
try {
  runtimeService.startProcessInstanceByKey("vacationRequest");
} catch (ActivitiException e) {
  e.printStackTrace();
}           

• 要想重新激活一個流程定義,可以調用repositoryService.activateProcessDefinitionXXX方法
• 也可以挂起一個流程執行個體:
  • 挂起時,流程不能繼續執行:比如,完成任務會抛出異常,異步操作(比如定時器)也不會執行.挂起流程執行個體可以調用runtimeService.suspendProcessInstance方法
  • 激活流程執行個體可以調用runtimeService.activateProcessInstanceXXX方法