title: If I use ObjectifyFilter I get error
body: <p>Ref: Objectify Version: 5.1.2, GWT:2.5.1, GAE:1.9.15  </p>
  
  <p>As per Objectify documentation, If I add ObjectifyFilter in web.xml, I get the following error:</p>
  
  <blockquote>
    <p>java.lang.NoSuchMethodError:
    java.util.concurrent.ConcurrentHashMap.keySet()Ljava/util/concurrent/ConcurrentHashMap$KeySetView;
      at
    com.googlecode.objectify.cache.PendingFutures.completeAllPendingFutures(PendingFutures.java:54)
      at
    com.googlecode.objectify.ObjectifyService$2.close(ObjectifyService.java:120)
      at
    com.googlecode.objectify.ObjectifyFilter.doFilter(ObjectifyFilter.java:49)
      at
    org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
      at
    com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
      at
    org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
      at
    com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:127)
      at
    org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
      at
    com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
      at
    org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
      at
    com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
      at
    org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
      at
    com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
      at
    org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
      at
    com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
      at
    org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
      at
    com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:366)
      at
    com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:349)
      at
    com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
      at
    org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
      at
    org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
      at
    org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
      at
    org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
      at
    org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
      at
    org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
      at
    com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:98)
      at
    org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
      at
    com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:491)
      at
    org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
      at org.mortbay.jetty.Server.handle(Server.java:326)     at
    org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
      at
    org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
      at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)  at
    org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)  at
    org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)  at
    org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
      at
    org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)</p>
  </blockquote>
  
  <p>If I don't use ObjectifyFilter in the web.xml, I get the following error:</p>
  
  <blockquote>
    <p>java.lang.IllegalStateException: You have not started an Objectify
    context. You are probably missing the ObjectifyFilter. If you are not
    running in the context of an http request, see the
    ObjectifyService.run() method.</p>
  </blockquote>
  
  <p>I made it work by doing the following in RemoteServiceServlet.</p>
  
  <pre><code>public void init()
  {
      session = ObjectifyService.begin();
  }
  
  public void destroy()
  {
      session.close();
  }
  </code></pre>
  
  <p>My question is,</p>
  
  <p>Why do I get error when I use ObjectifyFilter? It is as per documentation.</p>
  
  <p>What is that I am doing wrong?</p>