package servlet;
// Servlet开发所需要的包
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloServlet extends HttpServlet
{
  public void doGet(HttpServletRequest request,HttpServletResponse response)
throw IOException,ServletException
  {
   response.setContentType("text/html;charset=gb2312");
   PrintWriter out = response.getWriter();
   out.print("Servlet测试！");
  }
}

<servlet>
  <servlet-name>hello</servlet-name>
  <servlet-class>servlet.HelloServlet</servlet-class>
</serlvet>

<servlet-mapping>
  <servlet-name>hello</servlet-name>
  <url-pattern>/hello</url-pattern>
</servlet-mapping>

package servlet;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import javabean.*;
public class LoginProcess extends HttpServlet
{
  public void doGet(HttpServletRequest request,HttpServletResponse response)
   throws IOException,ServletException
  {
   // 第一步：获取用户的输入信息
   String username = request.getParameter("username");
   String userpass = request.getParameter("userpass");
   // 第二步：调用JavaBean
   User user = new User();
   user.setUsername(username);
   user.setUserpass(userpass);
   boolean b = user.check();
   // 第三步：选择一个界面对用户进行响应
   String forward;
   if(b)
     forward = "success.jsp";
   else
     forward = "failure.jsp";
   RequestDispatcher rd = request.getRequestDispatcher(forward);
   rd.forward(request,response);
  }
}

  <servlet>
   <servlet-name>process</servlet-name>
   <servlet-class>servlet.LoginProcess</servlet-class>
  </servlet>
  <servlet-mapping>
   <servlet-name>process</servlet-name>
   <url-pattern>/process</url-pattern>
  </servlet-mapping>

<%@ page contentType="text/html;charset=gb2312"%>
请登录<br>
<form name="form1" method="post" action="process">
  用户ID：<input type="text" name="username"><br>
  口令：<input type="password" name="userpass"><br>
    <input type="submit" value="登录"><input type="reset" value="重置">
</form>
<%@ include file="contact.jsp"%>

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