在 jBPM 商业流程中有一个 ProcessEventListener ，可以用来回调流程的执行过程，但是这个 Listener 的执行顺序非常奇怪。

首先我们先看看这个 interface

public interface ProcessEventListener {

  void beforeProcessStarted( ProcessStartedEvent event );
  void afterProcessStarted( ProcessStartedEvent event );
  void beforeProcessCompleted( ProcessCompletedEvent event );
  void afterProcessCompleted( ProcessCompletedEvent event );
  void beforeNodeTriggered( ProcessNodeTriggeredEvent event );
  void afterNodeTriggered( ProcessNodeTriggeredEvent event );
  void beforeNodeLeft( ProcessNodeLeftEvent event );
  void afterNodeLeft( ProcessNodeLeftEvent event );
  void beforeVariableChanged(ProcessVariableChangedEvent event);
  void afterVariableChanged(ProcessVariableChangedEvent event);

}

我相信大多数人看到这些方法回调大致可以猜测 afterProcessStarted 应该是在流程开始之后被调用，然而实际的调用顺序是这样的：

- beforeProcessStarted
  - beforeNodeTriggered
    - beforeNodeLeft
      - beforeNodeTriggered
        - beforeVariableChanged
          afterVariableChanged
        - beforeNodeLeft
          - beforeNodeTriggered
            - beforeNodeLeft
              - beforeNodeTriggered
                afterNodeTriggered
              afterNodeLeft
            - beforeNodeLeft
                beforeNodeTriggered
                afterNodeTriggered
              afterNodeLeft
            afterNodeTriggered
          afterNodeLeft
        afterNodeTriggered
      afterNodeLeft
    afterNodeTriggered
  afterProcessStarted

afterProcessStarted 会在流程结束时被调用。有人提过 bug 但是官方认为这是程序设计，所以使用文档的形式 将这种方式说明了。

查看源代码可以在 RuleExecutor 中可以看到：

jbpm listener

实验

假设有如下图的流程

jbpm process

那么打印所有的日志可以观察到：

- DefaultRuleContainer beforeVariableChanged ==>[ProcessVariableChanged(id=age; instanceId=age; oldValue=null; newValue=18; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterVariableChanged ==>[ProcessVariableChanged(id=age; instanceId=age; oldValue=null; newValue=18; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeProcessStarted ==>[ProcessStarted(name=BPTest; id=FlowTest.BPTest)]
- event ==>[ProcessStarted(name=BPTest; id=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeTriggered ==>[ProcessNodeTriggered(nodeId=4; id=0; nodeName=StartPoint; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeLeft ==>[ProcessNodeLeft(nodeId=4; id=0; nodeName=StartPoint; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeTriggered ==>[ProcessNodeTriggered(nodeId=7; id=1; nodeName= 年龄是否大于 18; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeLeft ==>[ProcessNodeLeft(nodeId=7; id=1; nodeName= 年龄是否大于 18; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeTriggered ==>[ProcessNodeTriggered(nodeId=2; id=2; nodeName=A1Task; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeLeft ==>[ProcessNodeLeft(nodeId=2; id=2; nodeName=A1Task; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeTriggered ==>[ProcessNodeTriggered(nodeId=6; id=3; nodeName=A2Task; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeLeft ==>[ProcessNodeLeft(nodeId=6; id=3; nodeName=A2Task; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeTriggered ==>[ProcessNodeTriggered(nodeId=3; id=4; nodeName=End; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeNodeLeft ==>[ProcessNodeLeft(nodeId=3; id=4; nodeName=End; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer beforeProcessCompleted ==>[ProcessCompleted(name=BPTest; id=FlowTest.BPTest)]
- DefaultRuleContainer afterProcessCompleted ==>[ProcessCompleted(name=BPTest; id=FlowTest.BPTest)]
- event ==>[ProcessCompleted(name=BPTest; id=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeLeft ==>[ProcessNodeLeft(nodeId=3; id=4; nodeName=End; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeTriggered ==>[ProcessNodeTriggered(nodeId=3; id=4; nodeName=End; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeLeft ==>[ProcessNodeLeft(nodeId=6; id=3; nodeName=A2Task; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeTriggered ==>[ProcessNodeTriggered(nodeId=6; id=3; nodeName=A2Task; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeLeft ==>[ProcessNodeLeft(nodeId=2; id=2; nodeName=A1Task; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeTriggered ==>[ProcessNodeTriggered(nodeId=2; id=2; nodeName=A1Task; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeLeft ==>[ProcessNodeLeft(nodeId=7; id=1; nodeName= 年龄是否大于 18; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeTriggered ==>[ProcessNodeTriggered(nodeId=7; id=1; nodeName= 年龄是否大于 18; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeLeft ==>[ProcessNodeLeft(nodeId=4; id=0; nodeName=StartPoint; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterNodeTriggered ==>[ProcessNodeTriggered(nodeId=4; id=0; nodeName=StartPoint; processName=BPTest; processId=FlowTest.BPTest)]
- DefaultRuleContainer afterProcessStarted ==>[ProcessStarted(name=BPTest; id=FlowTest.BPTest)]

reference