for循環拋出異常
<%@ page language="java" import="java.util.*" contentType="text/html; charset=UTF-8"
? ? pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>request內置對象</h1>
<%
? request.setCharacterEncoding("utf-8");
%>
?用戶名：<%=request.getParameter("usename") %><br>
?愛好：<%?
?String[] favorites=request.getParameterValues("favorite");?
?for(int i=0;i<favorites.length;i++)
?{
out.println(favorites[i]+" ");
?}
?%>
</body>
</html>
HTTP Status 500 – Internal Server Error
Type Exception Report
Message An exception occurred processing JSP page [/request.jsp] at line [14]
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?[/request.jsp]?at?line?[14]
11:??用戶名：<%=request.getParameter("usename")?%><br>
12:??愛好：<%?
13:??String[]?favorites=request.getParameterValues("favorite");?
14:??for(int?i=0;i<favorites.length;i++)
15:??{
16:? ?out.println(favorites[i]+" ");
17:??}
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:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)Root Cause
java.lang.NullPointerException org.apache.jsp.request_jsp._jspService(request_jsp.java:126) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:742) 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:742) 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.
2018-08-17
你的上一個跳轉頁面有信息沒有填，造成空指針異常，
空指針異常不能捕捉，解決方法就是將容易為空的字段加上非空判斷，阻止此字段為空時運行代碼造成報錯。
2018-07-11
加一句判斷非空?if(request.getparameterValues(favorite)!=null) ?{ ????String[]?favorites=request.getParameterValues("favorite");? ??????for(int?i=0;i<favorites.length;i++) ??????{ ????????out.println(favorites[i]+" "); ??????} ? ?}2018-07-11
2018-07-11