使用　XPAGER 分页标记V1.2　的问题

使用String s = new String(request.getParameter("key").getBytes("gb2312"),"ISO8859-1");出现以下错误500 Servlet Exception
java.lang.NullPointerException
at _xwzx._admin._modify_0list3__jsp._jspService(/ahedu/xwzx/admin/modify_list3.jsp:42)
at com.caucho.jsp.JavaPage.service(JavaPage.java:75)
at com.caucho.jsp.Page.subservice(Page.java:506)
at com.caucho.server.http.FilterChainPage.doFilter(FilterChainPage.java:182)
at com.caucho.server.http.Invocation.service(Invocation.java:315)
at com.caucho.server.http.CacheInvocation.service(CacheInvocation.java:135)
at com.caucho.server.http.RunnerRequest.handleRequest(RunnerRequest.java:344)
at com.caucho.server.http.RunnerRequest.handleConnection(RunnerRequest.java:274)
at com.caucho.server.TcpConnection.run(TcpConnection.java:139)
at java.lang.Thread.run(Thread.java:536)
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Resin 2.1.9 (built Tue Apr 15 14:28:40 PDT 2003)