检索 ArrayList 作为会话属性

Question

假设我得到 class:

import java.io.Serializable;


public class UrlEntry implements Serializable
{
    private String shortUrl;
    private String longUrl;
    private long clicks;


    public UrlEntry(String shortUrl, String longUrl, long clicks)
    {
        this.shortUrl = shortUrl;
        this.longUrl = longUrl;
        this.clicks = clicks;
    }


    public String getShortUrl()
    {
        return shortUrl;
    }
    public void setShortUrl(String shortUrl)
    {
        this.shortUrl = shortUrl;
    }
    public String getLongUrl()
    {
        return longUrl;
    }
    public void setLongUrl(String longUrl)
    {
        this.longUrl = longUrl;
    }
    public long getClicks()
    {
        return clicks;
    }
    public void setClicks(long clicks)
    {
        this.clicks = clicks;
    }

    public UrlEntry(){}


}

这是来自控制器 servlet 的代码

HttpSession session =  request.getSession(true);
ArrayList<UrlEntry> list = new ArrayList<UrlEntry>();
list.add(new UrlEntry("abc","site1.com",1));
list.add(new UrlEntry("def","site2.com",2));
list.add(new UrlEntry("ghi","site3.com",3));
session.setAttribute("urls", list);                     
response.sendRedirect("index.jsp");

这是来自 index.jsp 的部分代码这很好用

<%=request.getSession().getAttribute("urls")%>

但这不起作用：

<%=(ArrayList<UrlEntry>)request.getSession().getAttribute("urls")%>

有错误

UrlEntry cannot be resolved to a type
<%=(ArrayList<UrlEntry>)request.getSession().getAttribute("urls")%>

我做错了什么？我应该将 UrlEntry 声明为可序列化吗？也许构造函数有问题？

Answer 1

错误是由 JSP 编译器引发的。它告诉您需要将 UrlEntry 的导入指令添加到 JSP 页面。

Answer 2

您必须先在 jsp 页面中导入 UrlEntry class。

<%@page import="packageName.UrlEntry"%>

检索 ArrayList 作为会话属性

retreiving ArrayList as a session attribute

java

session

jsp

servlets

session-variables