JBPM3 token 'Token(/)'can't be signalled cause it is currently not positioned


public void testDeployProcessDefinition(){

JbpmContext context = configuration.createJbpmContext() ;
try {
ProcessDefinition pd = new ProcessDefinition(processDefinitionName) ;
JbpmUtil.deployProcessDefinition(context, pd) ;
} catch (Exception e) {
context.setRollbackOnly() ;
e.printStackTrace();
}finally{
context.close() ;
}
}public void testStartNewProcessInstance(){
JbpmContext context = configuration.createJbpmContext() ;
try {
ProcessInstance pi = JbpmUtil.startNewProcessInstance(context, processDefinitionName) ;
System.out.println("Current ProcessInstance Id : "+pi.getId());
} catch (Exception e) {
context.setRollbackOnly() ;
e.printStackTrace();
}finally{
context.close() ;
}
}public void testFinishFullProcessInstace(){
JbpmContext context = configuration.createJbpmContext() ;
try {
JbpmUtil.finishFullProcessInstace(context) ;
} catch (Exception e) {
context.setRollbackOnly() ;
e.printStackTrace();
}finally{
context.close() ;
}
}

public static void finishFullProcessInstace(JbpmContext context){

ProcessInstance pi = context.getProcessInstance(DataUtil.getProcessInstanceId()) ;

context.getSession().setFlushMode(FlushMode.ALWAYS) ;
 
while( ! ( pi.getRootToken().getNode() instanceof EndState ) ){
Node node = pi.getRootToken().getNode() ;
if( node instanceof StartState ){
System.out.println("StartState : "+node.getName());
pi.signal() ;
}else if(node instanceof State){
System.out.println("State : "+node.getName());
pi.signal() ;
}else if(node instanceof TaskNode){
System.out.println("TaskNode : "+node.getName());
pi.signal() ;
}else if(node instanceof Node){
System.out.println(" Node : "+node.getName());
}else{
System.out.println("Unknown Node : "+node.getName() );
}
} 
 
}
流程定义文件：
<?xml version="1.0" encoding="UTF-8"?><process-definition
  xmlns=""  name="qingjia">
   <start-state name="start">
      <transition name="" to="state1"></transition>
   </start-state>
   <state name="state1">
      <transition name="" to="task1"></transition>
   </state>
   <task-node name="task1">
      <transition name="" to="end1"></transition>
   </task-node>
   <end-state name="end1"></end-state>
</process-definition>当我部署完流程定义后（testDeployProcessDefinition()），然后开始一个流程实例（testStartNewProcessInstance()），当先把流程跑一边的时候，总是报如标题的错误。请问是哪里调用有问题啊？
org.jbpm.JbpmException: token 'Token(/)' can't be signalled cause it is currently not positioned in a node
at org.jbpm.graph.exe.Token.signal(Token.java:134)
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:597)
at org.hibernate.proxy.pojo.cglib.CGLIBLazyInitializer.invoke(CGLIBLazyInitializer.java:147)
at org.jbpm.graph.exe.Token$$EnhancerByCGLIB$$b441ab2e.signal(<generated>)
at org.jbpm.graph.exe.ProcessInstance.signal(ProcessInstance.java:251)
at com.lee.util.JbpmUtil.finishFullProcessInstace(JbpmUtil.java:33)
at com.lee.test.Test.testFinishFullProcessInstace(Test.java:73)
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:597)
at junit.framework.TestCase.runTest(TestCase.java:154)
at junit.framework.TestCase.runBare(TestCase.java:127)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:118)
at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:130)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)