Servlet中include方法和forward方法的区别_sevlet的include-优快云博客

本文介绍了一个基于Java的简单登录系统实现，包括登录页面的设计、登录验证逻辑及Servlet间的转发与包含机制。通过示例展示了如何使用JSP进行用户输入收集，以及如何利用Servlet进行业务逻辑处理。

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/*login.jsp*/

<%@ page contentType="text/html;charset=GBK" language="java" pageEncoding="GBK"%>

<body>

<form action="login.do" name="LoginForm" method="get">
用户名：<input type="text" name="uname"><br>
密码：<input type="password" name="upwd"><br>
<input type="hidden" name="uid" value="432022199008081888">
<input type="submit" value="登陆">
<input type="reset" value="重置">
</form>
</body>
</html>

/*LoginServlet*/

package com.session;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

  response.setContentType("text/html; charset=GBK");
  request.setCharacterEncoding("GBK");
  response.setCharacterEncoding("GBK");

  String uname = request.getParameter("uname");
  String upwd = request.getParameter("upwd");
  String uid = request.getParameter("uid");
  RequestDispatcher rd = request.getRequestDispatcher("forward.do");

  if ("".equals(uname) || "".equals(upwd)) {
   response.sendRedirect("bad.html");
  } else {
   rd.forward(request, response);
  }
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}

/*ForwardServlet*/

package com.session;

import java.io.IOException;
import java.io.PrintWriter;

public class ForwardServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

  response.setContentType("text/html");
  PrintWriter out = response.getWriter();

  request.setCharacterEncoding("GBK");
  String uname = request.getParameter("uname");
  String upwd = request.getParameter("upwd");
  String uid = request.getParameter("uid");

  out.println("<!DOCTYPE HTML PUBLIC /"-//W3C//DTD HTML 4.01 Transitional//EN/">");
  out.println("<HTML>");
  out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
  out.println(" <BODY>");

  out.println("uname: " + uname + "<br>");
  out.println("upwd: " + upwd + "<br>");
  out.println("uid: " + uid + "<br>");
  RequestDispatcher rd = request.getRequestDispatcher("include.do");
  rd.include(request, response);
  out.println(" </BODY>");
  out.println("</HTML>");
  out.flush();
  out.close();
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  doGet(request, response);

}

}

/*IncludeServlet*/

package com.session;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class IncludeServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

  response.setContentType("text/html");
  PrintWriter out = response.getWriter();
  out.println("<!DOCTYPE HTML PUBLIC /"-//W3C//DTD HTML 4.01 Transitional//EN/">");
  out.println("<HTML>");
  out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
  out.println(" <BODY>");
  out.print("    This is a forward servlet");
  out.println(" </BODY>");
  out.println("</HTML>");
  out.flush();
  out.close();
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}

其实Servlet的forward方法就是将请求继续往下传，因此在这个过程中，传递的参数一直都是可以访问到的

include的方法其实是将另一个servlet中的输出内容包含进来