Question

我正在尝试按照JSP和eve的教程在教程中编写相同的代码后仍然会收到以下错误。

java.lang.Error：未解决的compilationproblem：复制本地变量车。

我正在尝试使用以下代码运行servlet。

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Apache Tomcat / 7.0.53日志中提供了根本原因的完整堆栈跟踪。

Apache Tomcat / 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>

web.xml：

<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>

session.java

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
    }

}

Answer 1

由于您在运行时收到错误而不是编译时间，我不认为问题必须直接（如果有的话）使用您已经显示的代码。该代码是在打包WAR文件时编译的，而不是在部署WAR文件时编译的，如果你有WAR，我认为它编译得很好。

我猜测这个重复的变量是在JSP文件中定义的，它恰好也有一个名为＆＃34; cart＆＃34;的变量。 JSP文件是在即时编译的＃34;在运行时，通常在第一次请求时。如果你查看showcart.jsp，你应该看到真正的原因。堆栈跟踪似乎支持这一点，您可以通过将cart方法中的doGet重命名为其他内容来验证我说的内容 - 错误仍然会显示＆＃34; cart＆＃34;。如果您在showcart.jsp中看不到原因，可以发布其内容吗？

java.lang.Error：JSP中出现未解决的编译错误

1 个答案: