用JBPM做OA工作流时抛异常

今天在用JBPM做OA工作流，提交文档时抛org.jbpm.JbpmException: can't signal token 'null' (4): it is suspended
at org.jbpm.graph.exe.Token.signal(Token.java:181)
at org.jbpm.graph.exe.Token.signal(Token.java:139)
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$$EnhancerByCGLIB$$5cbb31cd.signal(<generated>)
at Jbmp_SubmitDocument5.testSubmitDocument(Jbmp_SubmitDocument5.java:22)
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 junit.framework.TestSuite.runTest(TestSuite.java:208)
at junit.framework.TestSuite.run(TestSuite.java:203)
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:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)

异常，看下数据库JBPM_TOKEN表中的ISSUSPENDED字段的值是TRUE，修改该字段值为FALSE便不报错了，但当把流跳到下一结点时又遇到一样的问题，有什么办法解决？求大神帮助

还有一个问题是获取某个用户的任务列表时获取不到，我又根据Hibernate 发的sql语句查找对应数据库，JBPM_TASKINSTANCE表中无数据，我明明已经将公文和流程互相绑定了，为什么没往数据库中插入数据，互绑的代码如下：
//创建流程实例，并与公文互相绑定
public class Jbpm_CreateProcessInstance4 extends TestCase {
static JbpmConfiguration jbpmConfiguration = JbpmConfiguration.getInstance();
public void testCreateProcessInstance(){
JbpmContext context = jbpmConfiguration.createJbpmContext();
//获取流程定义
ProcessDefinition definition = (ProcessDefinition) context.getGraphSession().findLatestProcessDefinition("测试流程");

//通过流程定义来创建一个流程实例
ProcessInstance processInstance = new ProcessInstance(definition);
//保存流程实例
context.save(processInstance);

Document doc = (Document)context.getSession().load(Document.class, 1);
System.err.println("document is:"+doc.getCreator());
//绑定流程到公文
processInstance.getContextInstance().createVariable("document", doc.getId());
//绑定公文到流程
doc.setProcessInstanceId(processInstance.getId());


context.close();
}
}

在线等，求大神解救，万分感谢！