一个最简单的Activity入门流程代码

1.创建maven工程并导入pom文件

<dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.1.9.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>4.1.9.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.activiti</groupId>
            <artifactId>activiti-engine</artifactId>
            <version>5.22.0</version>
        </dependency>
        <dependency>
            <groupId>org.activiti</groupId>
            <artifactId>activiti-spring</artifactId>
            <version>5.22.0</version>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.4.193</version>
        </dependency>
    </dependencies>

2.在resources目录下新建一个xml文件（VacationRequest.bpmn20.xml），用来表示一个流程图信息，其本质是对流程图的转化

<?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>

3.创建java类，编写一个最简单的流程

使用Activity服务的第一步即创建ProcessEngine实例，它是整个Activity的引擎，几乎所有的引用都是由它生成的。我代码中使用的是基于默认创建配置，因为方便测试。当然也能借助于Spring的解析和依赖注入功能来创建引擎

在Spring配置文件（applicationContext.xml）下添加bean即可

  <bean id="processEngineConfiguration" class="org.activiti.engine.impl.cfg.StandaloneProcessEngineConfiguration">

    <property name="jdbcUrl" value="jdbc:h2:mem:activiti;DB_CLOSE_DELAY=1000" />
    <property name="jdbcDriver" value="org.h2.Driver" />
    <property name="jdbcUsername" value="sa" />
    <property name="jdbcPassword" value="" />

    <property name="databaseSchemaUpdate" value="true" />

    <property name="jobExecutorActivate" value="false" />

    <property name="mailServerHost" value="mail.my-corp.com" />
    <property name="mailServerPort" value="5025" />
  </bean>

public class OnboardingRequest {
    public static void main(String[] args) {
        //基于默认创建配置
        ProcessEngineConfiguration cfg = new StandaloneInMemProcessEngineConfiguration()
                .setJdbcUrl("jdbc:h2:mem:activiti;DB_CLOSE_DELAY=1000")
                .setJdbcUsername("sa")
                .setJdbcPassword("")
                .setJdbcDriver("org.h2.Driver")
                .setDatabaseSchemaUpdate(ProcessEngineConfiguration.DB_SCHEMA_UPDATE_TRUE);
        ProcessEngine processEngine = cfg.buildProcessEngine();
        String pName = processEngine.getName();
        String ver = processEngine.VERSION;
        System.out.println("ProcessEngine:"+pName+",Version:"+ver);
        //基于配置文件创建ProcessEngine
/*        ProcessEngine processEngine = ProcessEngines.getDefaultProcessEngine();
        String pName = processEngine.getName();
        String ver = processEngine.VERSION;
        System.out.println("ProcessEngine:"+pName+",Version:"+ver);*/

        //发布一个流程实例，发布意味着Activity引擎会把bpmn 2.0.xml解析成可以执行的东西，“发布包”的所有流程定义都将被存到数据库中，这样当重启引擎时
        //它依然可以获得已发布的流程定义
        RepositoryService repositoryService = processEngine.getRepositoryService();
        Deployment deployment = repositoryService.createDeployment()
                .addClasspathResource("onboarding.bpmn20.xml").deploy();
//        ProcessDefinition processDefinition = repositoryService.createProcessDefinitionQuery()
//                .deploymentId(deployment.getId()).singleResult();
        System.out.println("Number of process definition :"+repositoryService.createProcessDefinitionQuery().count());

        //启动一个流程实例，流程定义是“蓝图”（标准），流程实例是它的一个运行的存在
        Map<String, Object> variables = new HashMap<String, Object>();
        variables.put("employeeName", "Xujia");
        variables.put("numbleOfDays", new Integer(4));
        variables.put("vacationMotivation", "I'm really really tired !");
        RuntimeService runtimeService = processEngine.getRuntimeService();
        ProcessInstance processInstance = runtimeService.startProcessInstanceByKey("vacationRequest", variables);
        //验证是否开启了一个流程实例
        System.out.println("Numble of process instance :" + runtimeService.createProcessInstanceQuery().count());

        //查询所有task
        TaskService taskService = processEngine.getTaskService();
        List<Task> tasks =taskService.createTaskQuery().taskCandidateGroup("management").list();
        for (Task task : tasks) {
            System.out.println("Task available:"+task.getName());
        }
        //完成整个任务
        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);

        //挂起、**一个流程定义（不同于工单的挂起，类似于模型的启停状态）
        repositoryService.suspendProcessDefinitionByKey("vacationRequest");
        try {
            //挂起流程定义后即无法创建新流程了，会报出异常
            runtimeService.startProcessInstanceByKey("vacationRequest");
        } catch (ActivitiException e) {
            e.printStackTrace();
        }
        //**一个流程定义：   repositoryService.activateProcessDefinitionXXX方法

    }
}