不知道为什么出现错误，求解决

Question

HTTP Status 500 - An exception occurred processing JSP page /index.jsp at line 33

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type Exception report

message An exception occurred processing JSP page /index.jsp at line 33

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /index.jsp at line 33

30: 		    <tr>
31: 		    	<% 
32: 			    	 ItemsDao action=new ItemsDao();
33: 			    	 Item item=action.getItemById(Integer.parseInt(request.getParameter("id")));
34: 			    	 if(item!=null)
35: 			    	 {
36: 			    	%>


Stacktrace:
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

root cause

java.lang.NumberFormatException: null
	java.lang.Integer.parseInt(Unknown Source)
	java.lang.Integer.parseInt(Unknown Source)
	org.apache.jsp.index_jsp._jspService(index_jsp.java:101)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

note The full stack trace of the root cause is available in the Apache Tomcat/7.0.56 logs.

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Apache Tomcat/7.0.56

Answer 1

很明显啊 java.lang.NumberFormatException 空指针异常