ControllerBean中如何实现弹出窗口

单据设置了简单工作流，单子提交之后审核人在消息中心审批此单子，工作流走到第一个自动节点的时候调XXControllerBean中的_passAudit(Context ctx, IObjectPK pk, IObjectValue model)方法，检测是否符合某项条件，如果不符合条件弹出窗口提示审核人进行手动修改。
比如：我在XXControllerBean中的_passAudit(Context ctx, IObjectPK pk, IObjectValue model)方法写了一段代码
if(kpqty.compareTo(ysqty)!=0){
String msg="申请数量："+kpqty+"，和应收数量："+ysqty+"不一致，相差："+kpqty.subtract(ysqty)+"吨，请修改应收数量！";
throw new BOSException(msg);
}
调试的时候可以走到此方法中，工作流也可以正常走完，但是后台有报错，实现不了弹窗。
报错如下：
2015-07-25 15:40:58 信息 [con.out] [2015-07-25 15:40:58,516 ERROR at
com.kingdee.bos.workflow.util.InvocationExecutor.execute(InvocationExecutor.java:37)]申请数量：151.47，和应收数
量：150.00不一致，相差：1.47吨，请修改应收数量！
com.kingdee.bos.BOSException: 申请数量：151.47，和应收数量：150.00不一致，相差：1.47吨，请修改应收数量！
at com.kingdee.eas.fi.xsfksq.app.XskpControllerBean._passAudit(XskpControllerBean.java:248)
at com.kingdee.eas.framework.app.AbstractCoreBillBaseControllerBean.passAudit
(AbstractCoreBillBaseControllerBean.java:81)
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 com.kingdee.bos.metadata.function.FunctionInvoke.innerLocalInvoke(FunctionInvoke.java:277)
at com.kingdee.bos.metadata.function.FunctionInvoke.localInvokeNoProxy(FunctionInvoke.java:117)
at com.kingdee.bos.workflow.biz.FunctionHelper.invokeAutomatic(FunctionHelper.java:86)
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 com.kingdee.bos.workflow.util.InvocationExecutor.execute(InvocationExecutor.java:28)
at com.kingdee.bos.workflow.transaction.WfTxInvoker.invoke(WfTxInvoker.java:33)
at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.kingdee.bos.workflow.metas.InvokeMethodDelegateControllerBean.invoke
(InvokeMethodDelegateControllerBean.java:77)
at com.kingdee.bos.workflow.metas.InvokeMethodDelegateControllerBean._invokeRequiresNew
(InvokeMethodDelegateControllerBean.java:24)
at com.kingdee.bos.workflow.metas.AbstractInvokeMethodDelegateControllerBean.invokeRequiresNew
(AbstractInvokeMethodDelegateControllerBean.java:28)
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 com.kingdee.bos.transaction.EJBTxFacade.TxInvokerBean.invoke(TxInvokerBean.java:116)
at com.kingdee.bos.transaction.EJBTxFacade.TxInvokerBean.INVOKE_REQUIRES_NEW(TxInvokerBean.java:69)
at com.kingdee.bos.transaction.EJBTxFacade.TxInvokerBean_LocalObjectImpl_2.INVOKE_REQUIRES_NEW(Unknown
Source)
at com.kingdee.bos.transaction.EJBTransactionProxy.invoke(EJBTransactionProxy.java:195)
at com.kingdee.bos.transaction.EJBTransactionProxy.invoke(EJBTransactionProxy.java:324)
at $Proxy143.invokeRequiresNew(Unknown Source)
at com.kingdee.bos.workflow.metas.InvokeMethodDelegate.invokeRequiresNew(InvokeMethodDelegate.java:43)
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 com.kingdee.bos.ResponseInvocationHandler.invoke(ResponseInvocationHandler.java:193)
at $Proxy142.invokeRequiresNew(Unknown Source)
at com.kingdee.bos.workflow.transaction.WfTxHelper.invokeRequiresNew(WfTxHelper.java:93)
at com.kingdee.bos.workflow.enactment.app.DefaultApplicationManager.invokeAutomaticRequiresNew
(DefaultApplicationManager.java:711)
at com.kingdee.bos.workflow.enactment.app.DefaultApplicationManager.invokeTool
(DefaultApplicationManager.java:596)
at com.kingdee.bos.workflow.enactment.app.DefaultApplicationManager.invokeApplication
(DefaultApplicationManager.java:339)
at com.kingdee.bos.workflow.enactment.ToolActivityRunner.start(ToolActivityRunner.java:86)
at com.kingdee.bos.workflow.enactment.WfActivity.activate(WfActivity.java:1242)
at com.kingdee.bos.workflow.enactment.WfProcess.transInternal(WfProcess.java:2697)
at com.kingdee.bos.workflow.enactment.WfEngine.trans(WfEngine.java:1191)
at com.kingdee.bos.workflow.enactment.WfEngine.transSupport(WfEngine.java:1155)
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 com.kingdee.bos.workflow.util.InvocationExecutor.execute(InvocationExecutor.java:28)
at com.kingdee.bos.workflow.transaction.WfTxInvoker.invoke(WfTxInvoker.java:33)
at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.kingdee.bos.workflow.metas.InvokeMethodDelegateControllerBean.invoke
(InvokeMethodDelegateControllerBean.java:77)
at com.kingdee.bos.workflow.metas.InvokeMethodDelegateControllerBean._invokeRequired
(InvokeMethodDelegateControllerBean.java:31)
at com.kingdee.bos.workflow.metas.AbstractInvokeMethodDelegateControllerBean.invokeRequired
(AbstractInvokeMethodDelegateControllerBean.java:46)
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 com.kingdee.bos.transaction.EJBTxFacade.TxInvokerBean.invoke(TxInvokerBean.java:116)
at com.kingdee.bos.transaction.EJBTxFacade.TxInvokerBean.INVOKE_REQUIRED(TxInvokerBean.java:57)
at com.kingdee.bos.transaction.EJBTxFacade.TxInvokerBean_LocalObjectImpl_2.INVOKE_REQUIRED(Unknown
Source)
at com.kingdee.bos.transaction.EJBTransactionProxy.invoke(EJBTransactionProxy.java:171)
at com.kingdee.bos.transaction.EJBTransactionProxy.invoke(EJBTransactionProxy.java:324)
at $Proxy143.invokeRequired(Unknown Source)
at com.kingdee.bos.workflow.metas.InvokeMethodDelegate.invokeRequired(InvokeMethodDelegate.java:61)
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 com.kingdee.bos.ResponseInvocationHandler.invoke(ResponseInvocationHandler.java:193)
at $Proxy142.invokeRequired(Unknown Source)
at com.kingdee.bos.workflow.transaction.WfTxHelper.invokeRequired(WfTxHelper.java:72)
at com.kingdee.bos.workflow.enactment.thread.TransRunner.transInWfTx(TransRunner.java:56)
at com.kingdee.bos.workflow.enactment.thread.TransRunner.run(TransRunner.java:35)
at com.kingdee.bos.util.ThreadPool$Worker.run(ThreadPool.java:164)

麻烦各位指教