计数器抱空指针错误
时间:2008-05-10 10:55:53
来源:论坛整理 作者: 编辑:chinaitzhe
下面是程序:
application.jsp
<%@ page language="java" contentType="text/html;charset=GB2312"%>
<%
int count = 0;
String counter_name = request.getParameter("counter_name"); //计数器名
try
{
count = Integer.parseInt((application.getAttribute(counter_name).toString()));
}
catch(Exception e){}
out.println("自从应用服务器启动后,此页面已经访问了" count "次");
count ;
application.setAttribute(counter_name,new Integer(count));
%>
以下是使用计数器的页面
test_application.jsp
<%@ page language="java" contentType="text/html;charset=GB2312"%>
<html>
<head>
<title>No Document </title>
<meta-equiv="Content-Type" content="text/html;charset=gb2312">
</head>
<body>
测试application的页面. <br>
<jsp:include page="application.jsp">
<jsp:param name="counter_name" value="test_application"/>
</jsp:include>
</body>
</html>
网友回复:报错信息如下j
ava.lang.NullPointerException
at org.apache.jsp.application_jsp._jspService(application_jsp.java:61)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:390)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:683)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:585)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:505)
at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:967)
at org.apache.jsp.test_005fapplication_jsp._jspService(test_005fapplication_jsp.java:64)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:390)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
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:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:212)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:634)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)
at java.lang.Thread.run(Thread.java:619)
网友回复:我在我的电脑上测试了,没有出错,正常显示
关键字：计数器,指针,错误,
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