title: Why always getting Nullpointer when doubleclicking link on XPage?
body: <p>I have a difficult problem: I always get a Nullpointer exception on my webpace, when I
  rapidly click on the same link. Or when I reload the page rapidly.
  This is the error I get:</p>
  
  <pre><code>java.lang.NullPointerException
      com.ibm.xsp.webapp.FacesServlet.acquireSyncToken(FacesServlet.java:285)
      com.ibm.xsp.webapp.FacesServletEx.serviceView(FacesServletEx.java:161)
      com.ibm.xsp.webapp.FacesServlet.service(FacesServlet.java:160)
      com.ibm.xsp.webapp.FacesServletEx.service(FacesServletEx.java:138)
      com.ibm.xsp.webapp.DesignerFacesServlet.service(DesignerFacesServlet.java:103)
      com.ibm.designer.runtime.domino.adapter.ComponentModule.invokeServlet(ComponentModule.java:576)
      com.ibm.domino.xsp.module.nsf.NSFComponentModule.invokeServlet(NSFComponentModule.java:1281)
      com.ibm.designer.runtime.domino.adapter.ComponentModule$AdapterInvoker.invokeServlet(ComponentModule.java:847)
      com.ibm.designer.runtime.domino.adapter.ComponentModule$ServletInvoker.doService(ComponentModule.java:796)
      com.ibm.designer.runtime.domino.adapter.ComponentModule.doService(ComponentModule.java:565)
      com.ibm.domino.xsp.module.nsf.NSFComponentModule.doService(NSFComponentModule.java:1265)
      com.ibm.domino.xsp.module.nsf.NSFService.doServiceInternal(NSFService.java:653)
      com.ibm.domino.xsp.module.nsf.NSFService.doService(NSFService.java:476)
      com.ibm.designer.runtime.domino.adapter.LCDEnvironment.doService(LCDEnvironment.java:341)
      com.ibm.designer.runtime.domino.adapter.LCDEnvironment.service(LCDEnvironment.java:297)
      com.ibm.domino.xsp.bridge.http.engine.XspCmdManager.service(XspCmdManager.java:272)
  </code></pre>
  
  <p>Question: Can someone explain in detail what this acquireSyncToken does? Maybe then I can find the bug...</p>
  
  <p>In my XPages I use</p>
  
  <pre><code>sessionScope.get(key) // same with applicationScope
  sessionScope.put(key, value) // same with applicationScope
  </code></pre>
  
  <p>a LOT ;)
  I tried very much, e.g. to wrap my lookups within</p>
  
  <pre><code>synchronize(applicationScope){
  // lookups and so on...
  }
  </code></pre>
  
  <p>and stuff like that, but that only made it worse, so I removed the synchronize-stuff...</p>
  
  <p><strong>Environment</strong>:</p>
  
  <pre><code>Domino Server 8.5.3 FP1
  XPages
  testing on modern Browsers like FF, Chrome
  MacOS / Win7
  </code></pre>
  
  <p><strong>Architecture</strong>:
  I have one BIG xPage, where I basically add some CustomControls and due to the current URL embed another XPage.
  Inside the CustomControls and XPages I have more Custom Controls and I added some Views as Datasources and did the wildest things with "repeat controls" and SSJS inside Computed Fields.
  The heavy-weight DB-Lookups are cached in the applicationScope.</p>
  
  <p>For more Info, please ask!
  Thanks in advance!</p>