Question

我有一个关于servlet和jsp的问题。

的Servlet

public class Servlet extends javax.servlet.http.HttpServlet {

    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        Integer i = new Integer(15);
        request.setAttribute("var", i);
        RequestDispatcher Dispatcher = getServletContext().getRequestDispatcher("/index.jsp");
        Dispatcher.forward(request, response);
    }

JSP页面：

<html>
  <head>
    <title></title>
  </head>
  <body>
        <form id="id" method="get" action="servlet">
            <%= (request.getAttribute("var")) %>
        </form>
  </body>
</html>

结果我希望看到15，但我看到null。为什么会这样？

Answer 1

请求参数从视图发送到控制器，请求属性用于传递当前请求中的数据以帮助构建新响应。因此，您should not use scriplets使用Expression Language访问请求属性：

<body>
    <!-- No need to use a form for this page -->
    The request attribute: ${var}
</body>

请注意，根据您当前的请求，您应该在servlet上执行GET请求。由于您的servlet名称是 servlet （我建议您立即更改），您应该访问以下URL：http://yourServerName/yourApplicationName/servlet

Answer 2

使用request.getAttribute（“var”）;

Answer 3

我不知道在servlet中但是在struts 2中你需要getter和setter方法来从jsp发送数据，你试试这个：

public class Servlet extends javax.servlet.http.HttpServlet 
{
    private Integer i;
    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        i = new Integer(15);
        request.setAttribute("var", i);
        RequestDispatcher Dispatcher = getServletContext().getRequestDispatcher("/index.jsp");
        Dispatcher.forward(request, response);
    }

  public Integer getI()
  {
     return i;
  }
  public void setI(Integer i)
  {
    this.i = i;
   }

 }//also lacked this

从Servlet向JSP发送变量

3 个答案: