JSP代码

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <!--action表示提交至服务器哪个资源 method表示以什么方式提交-->
	<form action="doLog" method="post">
	用户名:<input type="text" name="username"><br>
	密码:<input type="password" name="password"><br>
	<input type="submit" value="登录">
	</form>

</body>
</html>

jsp调用doLog

package Serv;

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

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 doLog
 */
@WebServlet("/doLog")
public class doLog extends HttpServlet {
	private static final long serialVersionUID = 1L;
    private static String name=null;
    /**
     * @see HttpServlet#HttpServlet()
     */
    public doLog() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//设置文档类型 字符集 
				response.setContentType("text/html;charset=utf-8");
				//获取输出流
				PrintWriter out=response.getWriter();
				request.setCharacterEncoding("utf-8");
				//获得客户端参数
				String uname=request.getParameter("username");
				name=uname;
				String upwd=request.getParameter("password");
				//请求重映像时路径区分大小写----相对路径
				//请求重映像时路径区分大小写----相对路径
				//请求重映像时路径区分大小写----相对路径
				//response.sendRedirect("DoWelcome");
				//请求重映像时路径区分大小写----绝对路径
				
				//不能使用equals会发生空指针异常
				//使用
				if (uname.equals("admin")&&upwd.equals("123")){
					response.sendRedirect("DoWelcome");
				} else {
					response.sendRedirect("login.jsp");
				}
//				if (!uname.equals("admin")||!upwd.equals("123")){
//					response.sendRedirect("login.jsp");
//				} else {
//					response.sendRedirect("DoWelcome");
//				}
				//response.sendRedirect(request.getContextPath()+"/DoWelcome");
				out.close();
	}
	
	public  String  Getname() {
		return name;
	}
	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

欢迎界面

package Serv;

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

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 DoWelcome
 */
@WebServlet("/DoWelcome")
public class DoWelcome extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DoWelcome() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");
		PrintWriter out=response.getWriter();
		doLog d=new doLog();
		String uname=d.Getname();
		out.println("Welcome "+uname);
		out.close();
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

登陆界面

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输入用户信息

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输入正确

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输入错误
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在这里插入图片描述

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