基于Servlet实现的简单登陆练习

时间静止不是简史

发布于 2020-07-26 00:15:43

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发布于 2020-07-26 00:15:43

文章被收录于专栏：Java探索之路Java探索之路

项目结构

效果演示

首先验证用户名，用户名密码正确则显示登陆成功的界面。然后记录访问次数，并且将访问访问量保存在本地文件中。而且，将编码格式配置在xml文件中，防止自己书写错误引起的编码错误的问题。

相关代码

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
 <!-- 配置全局属性，对请求和响应的编码格式进行配置 -->
   <context-param>
   		<param-name>reqcode</param-name>
   		<param-value>utf-8</param-value>
   </context-param>
   <context-param>
   		<param-name>repscode</param-name>
   		<param-value>text/html;charset=utf-8</param-value>
   </context-param>
   
  <display-name>12Login</display-name>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>com.bjsxt.servlet.LoginServlet</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>UserServlet</servlet-name>
    <servlet-class>com.bjsxt.servlet.UserServlet</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>MainServlet</servlet-name>
    <servlet-class>com.bjsxt.servlet.MainServlet</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>NumServlet</servlet-name>
    <servlet-class>com.bjsxt.servlet.NumServlet</servlet-class>
	
	<load-on-startup>1</load-on-startup><!-- 配置Servlet服务器启动加载 -->
  </servlet>

  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/login</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>UserServlet</servlet-name>
    <url-pattern>/user</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>MainServlet</servlet-name>
    <url-pattern>/main</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>NumServlet</servlet-name>
    <url-pattern>/num</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

LoginServlet.java

package com.bjsxt.servlet;

import java.io.IOException;

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

public class LoginServlet extends HttpServlet {
	@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		//获取SevletContext对象
		ServletContext sc = this.getServletContext();
		//获取共享数据
		String reqc = (String) sc.getInitParameter("reqcode");
		String respc = (String) sc.getInitParameter("repscode");
		
		//设置请求编码格式
		req.setCharacterEncoding(reqc);
		//设置响应编码格式
		resp.setContentType(respc);
		//获取session对象
		HttpSession session = req.getSession();
		String str= (session.getAttribute("flag")==null?"":"用户名或密码错误");
		session.invalidate();
		//获取请求信息
		//处理请求信息
		//相应处理结果
			//直接响应
		resp.getWriter().write("<html>");
		resp.getWriter().write("<head>");
		resp.getWriter().write("</head>");
		resp.getWriter().write("<body>");
		resp.getWriter().write("<form action='user' method='post'>");
		resp.getWriter().write("<font color='red'>"+str+"</font><br />");
		resp.getWriter().write("用户名：<input type='text' name='uname' /><br />");
		resp.getWriter().write("密码： <input type='password' name='pwd' /><br />");
		resp.getWriter().write("<input type='submit' value='登陆'>");
		resp.getWriter().write("</form>");
		resp.getWriter().write("</body>");
		resp.getWriter().write("</html>");
	}
}

UserServlet .java

package com.bjsxt.servlet;

import java.io.IOException;

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

public class UserServlet extends HttpServlet {
	@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		//获取SevletContext对象
		ServletContext sc = this.getServletContext();
		//获取共享数据
		String reqc = (String) sc.getInitParameter("reqcode");
		String respc = (String) sc.getInitParameter("repscode");
		
		//设置请求编码格式
		req.setCharacterEncoding(reqc);
		//设置响应编码格式
		resp.setContentType(respc); 
		//获取请求信息
		
		//处理请求信息
		String uname=req.getParameter("uname");
		String pwd=req.getParameter("pwd");
		if ("gaoqi".equals(uname)&&"123456".equals(pwd)) {
			
			//登陆成功
				//获取servletContext对象
				 //ServletContext sc = this.getServletContext();
				//从sc对象中获取计数器,没有就创建
				 Object obj = sc.getAttribute("nums");
				//判断
				 if (obj!=null) {
					//计数器自增
					 int nums=(int) obj;
					 nums++;
					 //存储计数器数据到servletContext对象上
			    	 sc.setAttribute("nums", nums);
				}else {
					 sc.setAttribute("nums", 1);
				}
			
			//创建session对象，获取用户名信息
			HttpSession hs = req.getSession();
			//hs是一个map，即键值对的集合，键名需要加引号，后来使用键名获取值时也要加引号
			hs.setAttribute("uname", uname);
			//响应处理结果
			resp.sendRedirect("main");
			
		}else {
			//登录失败
			
			//创建session并增加登陆失败标记
			HttpSession session = req.getSession();
			session.setAttribute("flag", "loginfalse");
			//响应处理结果
			resp.sendRedirect("login");
		}
		
		
	}
}

MainServlet .java

package com.bjsxt.servlet;

import java.io.IOException;

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

public class MainServlet extends HttpServlet {
	@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		//获取SevletContext对象
		ServletContext sc = this.getServletContext();
		//获取共享数据
		String reqc = (String) sc.getInitParameter("reqcode");
		String respc = (String) sc.getInitParameter("repscode");
		
		//设置请求编码格式
		req.setCharacterEncoding(reqc);
		//设置响应编码格式
		resp.setContentType(respc);
		//获取请求信息
			//获取servletContext对象
			//ServletContext sc = this.getServletContext();
			//获取计数器数据
			Object nums = sc.getAttribute("nums");
		//处理请求信息
		//响应请求结果
			//直接响应
			resp.getWriter().write("<html>");
			resp.getWriter().write("<head>");
			resp.getWriter().write("</head>");
			resp.getWriter().write("<body>");
			resp.getWriter().write("<h2>"+"欢迎"+req.getSession().getAttribute("uname")+"进入时间静止不是简史的博客"+"</h2>");
			resp.getWriter().write("<hr />");
			resp.getWriter().write("当前网页访问次数为："+nums);
			resp.getWriter().write("</body>");
			resp.getWriter().write("</html>");
			
			//请求转发
			//重定向
	}
}

NumServlet .java

package com.bjsxt.servlet;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;

public class NumServlet extends HttpServlet {

	//在服务器启动时将num.txt中的数据存储到ServletContext中去
	public void init() throws ServletException {
		
		//获取ServletContext对象
		ServletContext sc = this.getServletContext();
		//获取num.txt中存储的浏览器浏览的次数
			//获取nums.txt的绝对路径
			String path = sc.getRealPath("num/nums.txt");
			//创建File对象
			File f = new File(path);
			//读取nums.txt中的数据
			//获取资源流对象
			FileInputStream fis=null;
			InputStreamReader isr=null;
			BufferedReader br=null;
			
			try {
				fis=new FileInputStream(f);
				isr=new InputStreamReader(fis);
				br=new BufferedReader(isr);
				
				//读取
				String nums = br.readLine();
				//将数据存储到ServletContext中
				sc.setAttribute("nums", Integer.parseInt(nums));
			} catch (Exception e) {
				e.printStackTrace();
			}finally{
				try {
					br.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
				try {
					isr.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
				try {
					fis.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			
	}
	
	
	//在服务器关闭的时候，将nums.txt中的数据存储到servletContext中
	public void destroy() {
		//获取ServletContext对象
		ServletContext sc = this.getServletContext();
		//获取计数器数据
		int nums = (int) sc.getAttribute("nums");
		//将计数器数据存储到nums.txt文件中
			//获取nums.txt的绝对路径
			String path = sc.getRealPath("num/nums.txt");
			//获取file对象
			File f = new File(path);
			//获取资源流对象
			FileOutputStream fos=null;
			OutputStreamWriter osw=null;
			BufferedWriter bw=null;
			try {
				fos=new FileOutputStream(f);
				osw = new OutputStreamWriter(fos);
				bw = new BufferedWriter(osw);
				
				//将数据写入到num.txt中
				bw.write(nums+"");
				bw.flush();
			} catch (Exception e) {
				e.printStackTrace();
			}finally{
				try {
					bw.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
				try {
					osw.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
				try {
					fos.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
	}



}

源码分享：链接：https://pan.baidu.com/s/1LNtaEn7RgceO1Zez9DyLRA 提取码：w739

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原始发表：2019-04-16 ，如有侵权请联系 cloudcommunity@tencent.com 删除

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