在response.sendRedirect()方法后加return語句即可，如下：
response.sendRedirect("index.jsp");
return;
原因是：在程序中兩次調用了response.sendRedirect()方法。
jdk5.0文檔中很清楚地介紹了出現IllegalStateException異常的可能情況:
1）同一個頁面中再次調用response.sendRedirect()方法。
2）提交的URL錯誤，即不是個有效的URL。
filter中多次chain.doFilter(request, response);也會這樣，要保證一個filter只進行一次doFilter
java.lang.IllegalStateException
at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:405)
at org.apache.catalina.servlets.DefaultServlet.serveResource(DefaultServlet.java:779)
at org.apache.catalina.servlets.DefaultServlet.doGet(DefaultServlet.java:385)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:627)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:96)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.ebizer.framework.star.filter.CoreUrlRewriteFilter.doFilterInternal(CoreUrlRewriteFilter.java:120)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:581)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:843)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:679)
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1293)
at java.lang.Thread.run(Thread.java:595)