Activiti 流程启动的几种方式

最近在断断续续的学习activiti工作流引擎，为了增强自己对activiti的理解，特此将学习内容整理在博文上，方便自己回忆。

Activiti 的流程启动总结来说有四种启动方式，分别是根据key启动、根据processDefinitionId启动、根据message启动，通过ProcessInstanceBuilder启动。

1、processDefinitionKey启动

根据processDefinitionKey启动也就是根据流程定义文件的key启动，是activiti最常用的启动方式（流程定义文件，key为my-process），代码如下：

<process id="my-process">
    <startEvent id="start" />
    <sequenceFlow id="flow1" sourceRef="start" targetRef="someTask" />
    <userTask id="someTask" name="Activiti is awesome!" />
    <sequenceFlow id="flow2" sourceRef="someTask" targetRef="end" />
    <endEvent id="end" />
</process>

processDefinitionKey启动，代码如下：

@Test
@org.activiti.engine.test.Deployment(resources = "my-process.bpmn20.xml")
public void testStartProcessInstanceByKey() {

    RuntimeService runtimeService = activitiRule.getRuntimeService();

    Map<String, Object> map = Maps.newHashMap();
    map.put("name", "zhangxingr");
    map.put("sex", "man");
    map.put("age", "21");

    ProcessInstance processInstance = runtimeService.startProcessInstanceByKey("my-process", map);
    logger.info("processInstance = {}", processInstance);
}

2、processDefinitionId启动

@Test
@org.activiti.engine.test.Deployment(resources = "my-process.bpmn20.xml")
public void testStartProcessInstanceById() {

    RuntimeService runtimeService = activitiRule.getRuntimeService();

    Map<String, Object> map = Maps.newHashMap();
    map.put("name", "zhangxingr");
    map.put("sex", "man");
    map.put("age", "21");

    ProcessDefinition processDefinition = activitiRule.getRepositoryService()
        .createProcessDefinitionQuery().singleResult();

    ProcessInstance processInstance = runtimeService
        .startProcessInstanceById(processDefinition.getId(), map);
    logger.info("processInstance = {}, process'key = {}, process'name = {}",
    processInstance, processInstance.getProcessDefinitionKey(),
    processInstance.getName());
}

3、message启动

根据message启动就要复杂一些，需要改动一下流程定义文件的startEvent，增加messageEventDefinition，流程定义文件如下：

<message id="messageStart" name="my-message"/>
    <process id="my-process">
    <startEvent id="start">
    <messageEventDefinition messageRef="messageStart"/>
    </startEvent>
    <sequenceFlow id="flow1" sourceRef="start" targetRef="someTask" />
    <userTask id="someTask" name="Activiti is awesome!" />
    <sequenceFlow id="flow2" sourceRef="someTask" targetRef="end" />
    <endEvent id="end" />
</process>

message启动，代码如下：

@Test
@org.activiti.engine.test.Deployment(resources = "my-process-message.bpmn20.xml")
public void testMessageStart() {

    RuntimeService runtimeService = activitiRule.getRuntimeService();

    ProcessInstance processInstance = runtimeService
        .startProcessInstanceByMessage("my-message");

    logger.info("processInstance = {}", processInstance);
}

根据message启动底层源码实现最终其实还是会走到用processDefinitionId来启动来，所以建议直接使用processDefinitionId方式启动，底层代码如下：

public ProcessInstance execute(CommandContext commandContext) {

    if (messageName == null) {
      throw new ActivitiIllegalArgumentException("Cannot start process instance by message: message name is null");
    }

    MessageEventSubscriptionEntity messageEventSubscription = commandContext.getEventSubscriptionEntityManager().findMessageStartEventSubscriptionByName(messageName, tenantId);

    if (messageEventSubscription == null) {
      throw new ActivitiObjectNotFoundException("Cannot start process instance by message: no subscription to message with name '" + messageName + "' found.", MessageEventSubscriptionEntity.class);
    }

    String processDefinitionId = messageEventSubscription.getConfiguration();
    if (processDefinitionId == null) {
      throw new ActivitiException("Cannot start process instance by message: subscription to message with name '" + messageName + "' is not a message start event.");
    }

    DeploymentManager deploymentCache = commandContext.getProcessEngineConfiguration().getDeploymentManager();

    ProcessDefinition processDefinition = deploymentCache.findDeployedProcessDefinitionById(processDefinitionId);
    if (processDefinition == null) {
      throw new ActivitiObjectNotFoundException("No process definition found for id '" + processDefinitionId + "'", ProcessDefinition.class);
    }

    ProcessInstanceHelper processInstanceHelper = commandContext.getProcessEngineConfiguration().getProcessInstanceHelper();
    ProcessInstance processInstance = processInstanceHelper.createAndStartProcessInstanceByMessage(processDefinition, messageName, processVariables, transientVariables);

    return processInstance;
}

从上面可以看到，最终还是生成了一个processDefinitionId然后调createAndStartProcessInstanceByMessage来启动，具体可以去跟下源码。

4、processInstanceBuilder启动

@Test
@org.activiti.engine.test.Deployment(resources = "my-process.bpmn20.xml")
public void testProcessInstanceBuilder() {

    RuntimeService runtimeService = activitiRule.getRuntimeService();

    Map<String, Object> map = Maps.newHashMap();
    map.put("name", "zhangxingr");
    map.put("sex", "man");
    map.put("age", "21");

    ProcessInstanceBuilder builder = runtimeService.createProcessInstanceBuilder();
    ProcessInstance processInstance = builder.processDefinitionKey("my-process")
        .businessKey("businessKey001")
        .name("我的流程实例")
        .start();

    logger.info("processInstance = {}", processInstance);
}

到此Activiti 流程启动的几种方式介绍完成。