在不使用表单参数的情况下将参数从 JSP 页面传递到 servlet

Question

I have been trying to pass parameters from my welcome.jsp page to details.java servlet.But the value that I am getting in servlet details.java is null. 这是welcome.jsp的代码

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>

<% 
String n=(String)session.getAttribute("name");
if(n==null)response.sendRedirect("login.html");

%>
Hello there!!
<%
out.println(n+"<br>");
String u=(String)session.getAttribute("userid");
out.println(u);
HttpSession session1=request.getSession();  
session1.setAttribute("userid",u); 
%>


<h3>Click here to see your salary details</h3>
<form action="Details">

<button>Salary details</button>
</form>
<h3>Click here to see your other details</h3>
<form action="">
<button>Other</button>
</form>
</body>
</html>

这是servlet详细信息的代码。java

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    PrintWriter out=response.getWriter();
    out.println(request.getParameter("userid"));
    //out.println(userid+"<br>");
    
    response.getWriter().append("Served at: ").append(request.getContextPath());
}

我得到的 output 是

null Served at: /login

有什么方法可以在不使用表单的情况下将这些参数值传递给我的 servlet？

Answer 1

您应该使用核心库中的c:set元素并将 scope 设置为请求。 文档中的示例：

<c:set var="foo" scope="request" value="..."/>

不要忘记在 JSP 的顶部声明标签库：

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>