doPost 在转发 servlet 之后答案

【问题标题】：doPost after a forward servletsdoPost 在转发 servlet 之后
【发布时间】：2016-05-18 21:20:07
【问题描述】：

我是使用 JSP 和 servlet 的新手，所以我不知道我是否以正确的方式来做这件事。就这样吧。

我正在尝试使用我的 firstServlet 执行 doPost 以填充表，然后使用第二个我将尝试进行插入，但我需要 index.jsp 表中的数据，但是当我执行 secondServlet 时，我得到了一个空数据

index.html

    <%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!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>Insert title here</title>
</head>
<body>
    <table>
        <tr> 
            <td id="data"><%=(String)request.getAttribute("data") %> </td>
        </tr>
    </table>
    <form action="firstServlet" method="post">
        <input type="text" id="text1">
        <input type="submit" id="btn">
    </form>
    <form action="secondServlet" method="post">
        <input type="text" id="text2">
        <input type="submit" id="btn">
    </form>
</body>
</html>

firstServlet

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class firstServlet
 */
@WebServlet("/firstServlet")
public class firstServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public firstServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.getWriter().append("Served at: ").append(request.getContextPath());
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setAttribute("data", "Here's my data");
        request.getRequestDispatcher("index.jsp").forward(request, response);
        //doGet(request, response);
    }

}

secondServlet

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class secondServlet
 */
@WebServlet("/secondServlet")
public class secondServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public secondServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.getWriter().append("Served at: ").append(request.getContextPath());
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String s = (String) request.getAttribute("data");
        request.setAttribute("data", s);
        request.getRequestDispatcher("index.jsp").forward(request, response);
        //doGet(request, response);
    }

}

【问题讨论】：

标签： java spring jsp servlets model-view-controller

【解决方案1】：

使用HttpSession 对象很容易传递数据。

在您的第一个 servlet 的 doPost 中，您将拥有如下内容：

request.getSession().setAttribute("DATA", "Here's my data");

在第二个 Servlet 中，您可以像这样检索数据：

String myData = (String)request.getSession().getAttribute("DATA");

从现在开始，只要会话有效，该 DATA 属性就会保留在用户会话中。您可以使用以下方法从会话中删除属性：

session.removeAttribute("DATA"); //OR request.getSession().removeAttribute("DATA");

【讨论】：

@OscarFlores 不要忘记，如果某个答案对您有帮助，您可以点赞并接受它，以便其他用户更容易找到有用的答案