**摘要：**本文通过一个工作流Activiti框架的具体使用示例，具体详尽的介绍了工作流Activiti框架的使用方式。

本文分享自华为云社区《一个使用示例，五个操作步骤！从此轻松掌握项目中工作流的开发》，作者：攻城狮Chova。

本文通过一个工作流Activiti框架的具体使用示例，具体详尽的介绍了工作流Activiti框架的使用方式。包括创建流程，发布流程，启动一个流程实例，完成一个流程实例以及挂起和激活一个流程实例。通过对工作流Activiti的具体使用步骤的掌握，基本上就能够学会了工作流Activiti的工作流程和具体使用。

创建流程

要想操作Activiti引擎,需要通过org.activiti.engine.ProcessEngine实例暴露的服务.就可以操作一个org.activiti.engine.ProcessEngine
创建一个请假申请的工作业务流程:

发布流程

任何与“静态”资源有关的数据(比如流程定义)都可以通过RepositoryService访问,从概念上讲,所有静态数据都是Activiti的资源内容
在src/test/resources/org/activiti/test目录下创建一个新的xml文件 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>

为了让Activiti引擎知道这个流程,我们必须先进行[发布],发布意味着引擎会把BPMN 2.0 xml解析成可以执行的东西,发布包中的所有流程定义都会添加到数据库中.这样,当引擎重启时,它依然可以获得[已发布]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());

启动一个流程实例

把流程定义发布到Activiti引擎后,可以基于它发起新流程实例.
对每个流程定义,都可以有很多流程实例.流程定义是"蓝图",流程实例是它的一个运行的执行
所有与流程运行状态相关的东西都可以通过RuntimeService获得.有很多方法可以启动一个新流程实例.
可以在流程实例启动时添加一些流程变量, 因为第一个用户任务的表达式需要这些变量.流程变量经常会被用到,因为它们赋予来自同一个流程定义的不同流程实例的特别含义
流程变量是区分流程实例的关键
下面使用定义在流程定义xml 中的key来启动流程实例:

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());

完成任务

流程启动后,第一步就是用户任务.这是必须由系统用户处理的一个环节.
用户会有一个"任务列表",展示了所有必须由整个用户处理的任务.下面是对应的查询:

// 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());
}

为了让流程实例继续运行,我们**需要完成整个任务.**对Activiti来说,就是需要complete任务:

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);

然后流程实例就会进入到下一个环节
下一环节允许员工通过表单调整原始的请假申请.员工可以重新提交请假申请,这会使流程重新进入到第一个任务

挂起或激活一个流程

可以挂起一个流程定义,当挂起流程定义时,就不能创建新流程了,会抛出一个异常.可以通过RepositoryService挂起一个流程:

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

要想重新激活一个流程定义,可以调用repositoryService.activateProcessDefinitionXXX方法
也可以挂起一个流程实例:
挂起时,流程不能继续执行:比如,完成任务会抛出异常,异步操作(比如定时器)也不会执行.挂起流程实例可以调用runtimeService.suspendProcessInstance方法
激活流程实例可以调用runtimeService.activateProcessInstanceXXX方法

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5步带你掌握工作流Activiti框架的使用

创建流程

发布流程

启动一个流程实例

完成任务

挂起或激活一个流程

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