测试jsp登录页面，记录多个用户登录网站时的用户数

HTTP Status 500 – Internal Server Error

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Type Exception Report

Message An exception occurred processing JSP page [/index.jsp] at line [22]

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

org.apache.jasper.JasperException: An exception occurred processing JSP page [/index.jsp] at line [22]

19: <%
20:      Object o2=application.getAttribute("UserNumber");
21:      if(o2!=null){
22:     	 int number1=(Integer)o2;
23:     	 out.println("褰撳墠鐧诲綍鐢ㄦ埛"+number1+"涓紒"+"<br/>");
24:      }
25: %>


Stacktrace:
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:584)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:481)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

Root Cause

java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
	org.apache.jsp.index_jsp._jspService(index_jsp.java:133)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

Note The full stack trace of the root cause is available in the server logs.

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Apache Tomcat/8.5.32

 

后来发现是我在session.setAttribute方法中对于设置的用户数量，用了"UserNumber"，找不到错误时，改为"userNumber"就好了。疑惑，现在还是不知道为什么这样就不行了。