java.lang.Error:JSP中出现未解决的编译错误
在编写了教程中相同的代码之后,我试图遵循关于JSP和eve的教程,但仍然收到以下错误 错误:未解决的编译问题:重复的本地 可变购物车 我试图用以下代码运行servletjava.lang.Error:JSP中出现未解决的编译错误,java,jsp,Java,Jsp,在编写了教程中相同的代码之后,我试图遵循关于JSP和eve的教程,但仍然收到以下错误 错误:未解决的编译问题:重复的本地 可变购物车 我试图用以下代码运行servlet protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSessio
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
Cart cart = (Cart)session.getAttribute("cart");
if (cart == null) {
cart = new Cart();
}
cart.setTotalItems(7);
session.setAttribute("cart", cart);
getServletContext().getRequestDispatcher("/showcart.jsp").forward(request,response);
}
HTTP Status 500 - Servlet execution threw an exception
--------------------------------------------------------------------------------
type Exception report
message Servlet execution threw an exception
description The server encountered an internal error that prevented it from fulfilling this request.
exception
javax.servlet.ServletException: Servlet execution threw an exception
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause
java.lang.Error: Unresolved compilation problem:
Duplicate local variable cart
demo.Session.doGet(Session.java:32)
javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
注意,根本原因的完整堆栈跟踪可在Apache Tomcat/7.0.53日志中找到
ApacheTomcat/7.0.53 showcart.jsp:
<?xml version="1.0" encoding="ISO-8859-1" ?>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
<title>Insert title here</title>
</head>
<body>
<%@ page import= "demo.*" %>
<% Cart cart= (Cart)session.getAttribute("cart");%>
Items in cart : <%= cart.getTotalItems() %>
</body>
</html>
由于您是在运行时而不是在编译时得到错误,我认为问题不必直接与您所展示的代码有关(如果有的话)。这段代码是在打包WAR文件时编译的,而不是在部署WAR文件时编译的,如果您有WAR文件,我假设它编译得很好
我猜这个重复的变量是在JSP文件中定义的,它碰巧还有一个名为“cart”的变量。JSP文件通常在第一次请求时在运行时“动态”编译。如果您查看
showcart.jsp
,您应该会看到真正的原因。堆栈跟踪似乎支持这一点,您可以通过将doGet
方法中的cart
重命名为其他内容来验证我所说的内容——错误仍然是“cart”。如果在showcart.jsp
中看不到原因,可以发布其内容吗?在哪一行出现错误?可以给出完整的堆栈跟踪吗?您使用的是哪个servlet容器?雄猫?什么版本?@AlvinThompson使用Tomcat 7.0还请说明上面的doGet
方法属于哪个类,并添加web.xml
文件的相关部分(servlet
和servlet映射
)。谢谢。我想这节课是课时
。让我想想…+1-同时看看生成的“showCart.java”文件,看看java编译器到底在抱怨什么。@StephenC?!哇,我一直在看你的节目!祝你晚会好运。:)@史蒂芬奇:如果你不是美国人,那么有一位名叫斯蒂芬·科尔伯特的名人。阿尔文——当你知道美国以外的人对美国文化了解很多时,你可能会感到惊讶。s/we's/think we/p:-)
<servlet>
<description></description>
<display-name>Session</display-name>
<servlet-name>Session</servlet-name>
<servlet-class>demo.Session</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Session</servlet-name>
<url-pattern>/Session</url-pattern>
</servlet-mapping>
</web-app>
package demo;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* Servlet implementation class Session
*/
public class Session extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public Session() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
Cart cart = (Cart)session.getAttribute("cart");
if (cart == null) {
cart = new Cart();
}
cart.setTotalItems(7);
session.setAttribute("cart", cart);
getServletContext().getRequestDispatcher("/showcart.jsp").forward(request,response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
}