Java 在jsp中调用request.getAttribute时,该属性为null
它通过单击a href调用ServletJava 在jsp中调用request.getAttribute时,该属性为null,java,jsp,servlets,web,Java,Jsp,Servlets,Web,它通过单击a href调用Servlet <li ><a href="<%=request.getContextPath() %>/ProviderServlet">privilegeManagement</a></li> 此代码包含在main.jsp中的navigation.jsp中 <%@ page language="java" contentType="text/html; charset=UTF-8
<li ><a href="<%=request.getContextPath() %>/ProviderServlet">privilegeManagement</a></li>
此代码包含在main.jsp中的navigation.jsp中
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@page import="java.util.*"%>
<%@page import="com.chenfeng.javabean.ProviderArchives"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!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>main</title>
</head>
<body>
<%@ include file="navigation.jsp"%>
<div>
<%@ include file="management.jsp"%>
</div>
<div>
<%
String k = (String)request.getAttribute("hu");
out.println(k);
%>
<c:forEach items="${list}" var="item">
<tr>
<td>${item.provideID() }</td>
<td>${item.GID }</td>
<td>${item.Gname }</td>
<td>${item.PID }</td>
<td>${item.TEL }</td>
<td>${item.ADDR }</td>
<td>
<a href="QueryUserByIdServlet?id=${item.provideID }">Modify</a>
<a href="DeleteUserServlet?id=${item.provideID }">Delete</a>
</td>
</tr>
</c:forEach>
</div>
</body>
</html>
然后是我的servlet
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
ProviderDao pd = new ProviderDao();
List<ProviderArchives> list = pd.getArchives();
String str = "chenfeng";
req.setAttribute("list", list);
req.setAttribute("hu" , str);
getServletContext().getRequestDispatcher("/jsp/main.jsp").forward(req,resp);
}
@覆盖
受保护的void doGet(HttpServletRequest-req,HttpServletResponse-resp)抛出ServletException,IOException{
//TODO自动生成的方法存根
ProviderDao pd=新ProviderDao();
List List=pd.getArchives();
String str=“晨风”;
请求设置属性(“列表”,列表);
请求设置属性(“hu”,str);
getServletContext().getRequestDispatcher(“/jsp/main.jsp”).forward(req,resp);
}
然后是我的main.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@page import="java.util.*"%>
<%@page import="com.chenfeng.javabean.ProviderArchives"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>main</title>
</head>
<body>
<%@ include file="navigation.jsp"%>
<div>
<%@ include file="management.jsp"%>
</div>
<div>
<%
String k = (String)request.getAttribute("hu");
out.println(k);
%>
<c:forEach items="${list}" var="item">
<tr>
<td>${item.provideID() }</td>
<td>${item.GID }</td>
<td>${item.Gname }</td>
<td>${item.PID }</td>
<td>${item.TEL }</td>
<td>${item.ADDR }</td>
<td>
<a href="QueryUserByIdServlet?id=${item.provideID }">Modify</a>
<a href="DeleteUserServlet?id=${item.provideID }">Delete</a>
</td>
</tr>
</c:forEach>
</div>
</body>
</html>
主要的
${item.provideID()}
${item.GID}
${item.Gname}
${item.PID}
${item.TEL}
${item.ADDR}
然后,当我在服务器上运行时,它显示如下
提前感谢您的帮助 这很清楚。在转发
Servlet上下文对象时,可以设置请求对象的属性。
而不是:
getServletContext().getRequestDispatcher("/jsp/main.jsp").forward(req,resp);
写:
req.getRequestDispatcher("/jsp/main.jsp").forward(req,resp);
实际上,这段代码没有任何原因。但是eclipse遇到了问题。在我删除build目录中的类文件并重新构建它之后,真正的问题日志输出。您从未使用属性hu
,那么为什么它甚至在那里?您是否检查过以确保list
属性不为空?检查您的服务器日志我想一定有一个异常,您没有注意到这不是原因,我以前使用过您的建议。getServletContext()是项目的get absolute path,但req.getRequestDispatcher是相对路径。@JingHu然后,正如Tim所说,检查列表变量。它可能是空的。