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Flowable6 – 事件
貌似从来没有专门介绍过Flowable的事件，只是在流程设计器部分提到过，那么就总结一下吧。
Flowable所有的事件类型，可以参见枚举：
org.flowable.common.engine.api.delegate.event.FlowableEngineEventType
比如最常用的：
/**
* A task has been created. This is thrown when task is fully initialized (before TaskListener.EVENTNAME_CREATE).
*/
TASK_CREATED,
/**
* A task has been completed. Dispatched before the task entity is deleted ( #ENTITY_DELETED). If the task is part of a process, this event is dispatched before the process moves on, as a
* result of the task completion. In that case, a #ACTIVITY_COMPLETED will be dispatched after an event of this type for the activity corresponding to the task.
*/
TASK_COMPLETED,
/**
* A process instance has been started. Dispatched when starting a process instance previously created. The event PROCESS_STARTED is dispatched after the associated event ENTITY_INITIALIZED and
* after the variables have been set.
*/
PROCESS_STARTED,
/**
* A process has been completed. Dispatched after the last activity is ACTIVITY_COMPLETED. Process is completed when it reaches state in which process instance does not have any transition to
* take.
*/
PROCESS_COMPLETED
这些事件是如何触发的呢？在AbstractEngineConfiguration内初始化了事件的Dispatcher：
public void initEventDispatcher() {
if (this.eventDispatcher == null) {
this.eventDispatcher = new FlowableEventDispatcherImpl();
}
//省略...
}
调用Dispatcher的dispatchEvent来触发事件，比如：
eventDispatcher.dispatchEvent(
FlowableTaskEventBuilder.createEntityEvent(
FlowableEngineEventType.TASK_CREATED,
task
),
processEngineConfiguration.getEngineCfgKey()
);
如何自定义监听这些事件呢？有两个办法：
- 像之前介绍的那样，在流程设计时，加入自定义的事件处理类。
- 在初始化ProcessEngineConfiguration时定义自己的处理类。
简单说一下第二种方法，首先需要实现接口：
public interface FlowableEventListener {
void onEvent(FlowableEvent var1);
boolean isFailOnException();
boolean isFireOnTransactionLifecycleEvent();
String getOnTransaction();
}
然后在实例化ProcessEngineConfiguration时引入实现类的集合：
configuration.setEventListeners(new ArrayList<FlowableEventListener>(){
{
add(new FlowableEventListenerImpl());
}
});
最后，想特别说一下：
/**
* A multi-instance activity has met its condition and completed successfully.
*/
MULTI_INSTANCE_ACTIVITY_COMPLETED_WITH_CONDITION
这个事件的触发条件：
- 多实例情况下。
- 达到了多实例节点的结束条件，也就是Completion condition的表达式为True。
这个事件比较有用，比如：流程的会签(多实例)节点达到结束条件时，可以清理一下冗余的数据，或者发送一条通知消息。
以上，就是关于事件的介绍，如有错误，欢迎指正。
