500 Servlet Exception

java.lang.NullPointerException
	at com.caucho.server.connection.AbstractHttpResponse.sendRedirect(AbstractHttpResponse.java:547)
	at com.xfz.servlet.CountArticle.doPost(CountArticle.java:58)
	at com.xfz.servlet.CountArticle.doGet(CountArticle.java:36)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:115)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:92)
	at com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChain.java:106)
	at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:173)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:229)
	at com.caucho.server.hmux.HmuxRequest.handleRequest(HmuxRequest.java:420)
	at com.caucho.server.port.TcpConnection.run(TcpConnection.java:511)
	at com.caucho.util.ThreadPool.runTasks(ThreadPool.java:520)
	at com.caucho.util.ThreadPool.run(ThreadPool.java:442)
	at java.lang.Thread.run(Thread.java:619)

Resin-3.0.22 (built Mon, 13 Nov 2006 09:32:38 PST)