jbpm4.3 修复 fork join bug

    在jbpm4.3 中使用 fork 分支，如果使用了assignmentHandler 在最后一个分支join的时候 会报如下的错误信息。
  
     INFO - Log4jLog.info(54) | exception while executing command org.jbpm.pvm.internal.cmd.CompositeCmd@1cd1e4e

java.lang.NullPointerException
at org.jbpm.pvm.internal.wire.usercode.UserCodeReference.getProcessDefinition(UserCodeReference.java:75)
at org.jbpm.pvm.internal.wire.usercode.UserCodeReference.getObject(UserCodeReference.java:60)
at org.jbpm.pvm.internal.wire.usercode.UserCodeReference.getObject(UserCodeReference.java:51)
at org.jbpm.pvm.internal.model.ExecutionImpl.initializeAssignments(ExecutionImpl.java:759)
at org.jbpm.jpdl.internal.activity.TaskActivity.execute(TaskActivity.java:95)
at org.jbpm.jpdl.internal.activity.TaskActivity.execute(TaskActivity.java:58)
at org.jbpm.pvm.internal.model.op.ExecuteActivity.perform(ExecuteActivity.java:60)
at org.jbpm.pvm.internal.model.ExecutionImpl.performAtomicOperationSync(ExecutionImpl.java:656)
at org.jbpm.pvm.internal.model.ExecutionImpl.fire(ExecutionImpl.java:566)
at org.jbpm.pvm.internal.model.ExecutionImpl.take(ExecutionImpl.java:472)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:197)
at org.jbpm.pvm.internal.model.ExecutionImpl_$$_javassist_61.take(ExecutionImpl_$$_javassist_61.java)
at org.jbpm.jpdl.internal.activity.JoinActivity.execute(JoinActivity.java:93)
at org.jbpm.jpdl.internal.activity.JoinActivity.execute(JoinActivity.java:49)
at org.jbpm.pvm.internal.model.op.ExecuteActivity.perform(ExecuteActivity.java:60)
at org.jbpm.pvm.internal.model.ExecutionImpl.performAtomicOperationSync(ExecutionImpl.java:656)
at org.jbpm.pvm.internal.model.ExecutionImpl.performAtomicOperation(ExecutionImpl.java:616)
at org.jbpm.pvm.internal.model.ExecutionImpl.signal(ExecutionImpl.java:417)
at org.jbpm.pvm.internal.model.ExecutionImpl.signal(ExecutionImpl.java:403)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:197)
at org.jbpm.pvm.internal.model.ExecutionImpl_$$_javassist_61.signal(ExecutionImpl_$$_javassist_61.java)
at org.jbpm.pvm.internal.task.TaskImpl.complete(TaskImpl.java:194)
at org.jbpm.pvm.internal.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:65)
at org.jbpm.pvm.internal.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:32)
at org.jbpm.pvm.internal.cmd.CompositeCmd.execute(CompositeCmd.java:43)
at org.jbpm.pvm.internal.cmd.CompositeCmd.execute(CompositeCmd.java:35)
   
     在网上经过海量信息的查找，找到了一个解决方法，还是临远大哥是牛人。如下：

      这是jbpm-4.3的一个bug，修改修改ExecutionImpl的原代码。
      修改方法见这里。
       http://community.jboss.org/thread/146754?tstart=0

      为方便大家，我把已经修改好的jbpm.jar 传上来（已经经过测试，bug的确修复了）