我在一个Filter里面，语句 chain.doFilter(request,response)弹出空指针异常，求大神解答。具体的异常信息见下：
com.ibm.websphere.servlet.error.ServletErrorReport: java.lang.NullPointerExceptionRoot Cause:java.lang.NullPointerExceptionnullStackTrace:java.lang.NullPointerExceptioncom.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:152)soon.servlet.SoonFilter.doFilter(SoonFilter.java:29)com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:188)com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:116)com.ibm.ws.webcontainer.filter.WebAppFilterChain._doFilter(WebAppFilterChain.java:77)com.ibm.ws.webcontainer.filter.WebAppFilterManager.doFilter(WebAppFilterManager.java:908)com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:934)com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:502)com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:181)com.ibm.ws.webcontainer.servlet.CacheServletWrapper.handleRequest(CacheServletWrapper.java:91)com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:864)com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1592)com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:186)com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:452)com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:511)com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:305)com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.ready(HttpInboundLink.java:276)com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.sendToDiscriminators(NewConnectionInitialReadCallback.java:214)com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.complete(NewConnectionInitialReadCallback.java:113)com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1646)