java.lang.NullPointerException
    at SurveyServlet.filterHtml(SurveyServlet.java:59)
    at SurveyServlet.doPost(SurveyServlet.java:30)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:228)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:216)
    at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:866)
    at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:716)
    at org.apache.tomcat.(AprEndpoint.java:1498)
    at java.lang.Thread.run(Thread.java:619)

空指针还是要看代码的 建议lz贴关键代码

谢谢  我检查一下 是代码问题。