Activiti - 多实例服务任务本身在循环中时出现异常答案

【问题标题】：Activiti - exception when multi-instance service task itself inside a loopActiviti - 多实例服务任务本身在循环中时出现异常
【发布时间】：2020-05-08 00:05:38
【问题描述】：

我有以下过程。在该过程中有一个多实例服务任务 (Service Task 3)，它本身就是循环的一部分。

问题是我在MyProcess 完成后收到以下异常。

但是，如果我使 Service Task 3 不是多实例，或者如果我使 Service Task 3 不是更大循环的一部分，那么我不会得到异常。因此，我提到的案例特别发生了异常。

org.activiti.engine.impl.pvm.PvmException: already taking a transition
at org.activiti.engine.impl.persistence.entity.ExecutionEntity.take(ExecutionEntity.java:453) ~[activiti-engine-5.22.0.jar:5.22.0]
at org.activiti.engine.impl.persistence.entity.ExecutionEntity.take(ExecutionEntity.java:438) ~[activiti-engine-5.22.0.jar:5.22.0]
at org.activiti.engine.impl.bpmn.behavior.BpmnActivityBehavior.performOutgoingBehavior(BpmnActivityBehavior.java:140) ~[activiti-engine-5.22.0.jar:5.22.0]
at org.activiti.engine.impl.bpmn.behavior.BpmnActivityBehavior.performDefaultOutgoingBehavior(BpmnActivityBehavior.java:66) ~[activiti-engine-5.22.0.jar:5.22.0]
at org.activiti.engine.impl.bpmn.behavior.FlowNodeActivityBehavior.leave(FlowNodeActivityBehavior.java:44) ~[activiti-engine-5.22.0.jar:5.22.0]
at org.activiti.engine.impl.bpmn.behavior.SequentialMultiInstanceBehavior.leave(SequentialMultiInstanceBehavior.java:75) ~[activiti-engine-5.22.0.jar:5.22.0]
at org.activiti.engine.impl.bpmn.behavior.MultiInstanceActivityBehavior.execute(MultiInstanceActivityBehavior.java:98) ~[activiti-engine-5.22.0.jar:5.22.0]
at org.activiti.engine.impl.bpmn.behavior.SequentialMultiInstanceBehavior.execute(SequentialMultiInstanceBehavior.java:90) ~[activiti-engine-5.22.0.jar:5.22.0]
at org.activiti.engine.impl.pvm.runtime.AtomicOperationActivityExecute.execute(AtomicOperationActivityExecute.java:60) ~[activiti-engine-5.22.0.jar:5.22.0]
at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:97) ~[activiti-engine-5.22.0.jar:5.22.0]

xml 是：

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:activiti="http://activiti.org/bpmn" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:omgdc="http://www.omg.org/spec/DD/20100524/DC" xmlns:omgdi="http://www.omg.org/spec/DD/20100524/DI" typeLanguage="http://www.w3.org/2001/XMLSchema" expressionLanguage="http://www.w3.org/1999/XPath" targetNamespace="http://www.activiti.org/test">
  <process id="myProcess" name="My process" isExecutable="true">
    <startEvent id="startevent1" name="Start"></startEvent>
    <endEvent id="endevent1" name="End"></endEvent>
    <serviceTask id="servicetask1" name="Service Task 1" activiti:delegateExpression="${serviceTask1}"></serviceTask>
    <sequenceFlow id="flow1" sourceRef="startevent1" targetRef="servicetask1"></sequenceFlow>
    <serviceTask id="servicetask2" name="Service Task 2" activiti:delegateExpression="${serviceTask2}"></serviceTask>
    <exclusiveGateway id="exclusivegateway1" name="Exclusive Gateway"></exclusiveGateway>
    <sequenceFlow id="flow2" sourceRef="servicetask1" targetRef="exclusivegateway1"></sequenceFlow>
    <sequenceFlow id="flow3" name="list not empty" sourceRef="exclusivegateway1" targetRef="servicetask2">
      <conditionExpression xsi:type="tFormalExpression"><![CDATA[{!isEmpty}]]></conditionExpression>
    </sequenceFlow>
    <serviceTask id="servicetask3" name="Service Task 3" activiti:delegateExpression="${serviceTask3}">
      <multiInstanceLoopCharacteristics isSequential="true" activiti:collection="myList" activiti:elementVariable="element"></multiInstanceLoopCharacteristics>
    </serviceTask>
    <sequenceFlow id="flow5" sourceRef="servicetask2" targetRef="servicetask3"></sequenceFlow>
    <sequenceFlow id="flow6" name="list empty" sourceRef="exclusivegateway1" targetRef="endevent1">
      <conditionExpression xsi:type="tFormalExpression"><![CDATA[${myList.isEmpty()}]]></conditionExpression>
    </sequenceFlow>
  </process>
  <bpmndi:BPMNDiagram id="BPMNDiagram_myProcess">
    <bpmndi:BPMNPlane bpmnElement="myProcess" id="BPMNPlane_myProcess">
      <bpmndi:BPMNShape bpmnElement="startevent1" id="BPMNShape_startevent1">
        <omgdc:Bounds height="35.0" width="35.0" x="180.0" y="250.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="endevent1" id="BPMNShape_endevent1">
        <omgdc:Bounds height="35.0" width="35.0" x="443.0" y="360.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="servicetask1" id="BPMNShape_servicetask1">
        <omgdc:Bounds height="55.0" width="105.0" x="280.0" y="240.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="servicetask2" id="BPMNShape_servicetask2">
        <omgdc:Bounds height="55.0" width="105.0" x="576.0" y="240.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="exclusivegateway1" id="BPMNShape_exclusivegateway1">
        <omgdc:Bounds height="40.0" width="40.0" x="440.0" y="247.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="servicetask3" id="BPMNShape_servicetask3">
        <omgdc:Bounds height="55.0" width="105.0" x="576.0" y="130.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNEdge bpmnElement="flow1" id="BPMNEdge_flow1">
        <omgdi:waypoint x="215.0" y="267.0"></omgdi:waypoint>
        <omgdi:waypoint x="280.0" y="267.0"></omgdi:waypoint>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="flow2" id="BPMNEdge_flow2">
        <omgdi:waypoint x="385.0" y="267.0"></omgdi:waypoint>
        <omgdi:waypoint x="440.0" y="267.0"></omgdi:waypoint>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="flow3" id="BPMNEdge_flow3">
        <omgdi:waypoint x="480.0" y="267.0"></omgdi:waypoint>
        <omgdi:waypoint x="576.0" y="267.0"></omgdi:waypoint>
        <bpmndi:BPMNLabel>
          <omgdc:Bounds height="14.0" width="100.0" x="489.0" y="267.0"></omgdc:Bounds>
        </bpmndi:BPMNLabel>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="flow5" id="BPMNEdge_flow5">
        <omgdi:waypoint x="628.0" y="240.0"></omgdi:waypoint>
        <omgdi:waypoint x="628.0" y="185.0"></omgdi:waypoint>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="flow6" id="BPMNEdge_flow6">
        <omgdi:waypoint x="460.0" y="287.0"></omgdi:waypoint>
        <omgdi:waypoint x="460.0" y="360.0"></omgdi:waypoint>
        <bpmndi:BPMNLabel>
          <omgdc:Bounds height="14.0" width="100.0" x="470.0" y="309.0"></omgdc:Bounds>
        </bpmndi:BPMNLabel>
      </bpmndi:BPMNEdge>
    </bpmndi:BPMNPlane>
  </bpmndi:BPMNDiagram>
</definitions>

Activiti 版本是 5.22.0。

有人遇到过这个问题可以帮忙吗？

【问题讨论】：

你能在xml视图中分享你的过程吗？你用的是什么版本的activiti？
我现在添加了。

标签： activiti bpmn

【解决方案1】：

这似乎是一个空集合的错误。

引用Activiti Ticket tracker (Issue 748):

当我们正在循环的集合在循环后的任何时候变为空时，我正面临一个多实例任务的新问题，这些任务因 PvmException("already getting a transition") 而失败。

您应该尝试在循环之前创建一个新的不可修改列表。检查原始列表不为空后，创建一个新列表以进行循环。

【讨论】：