JavaWeb学习笔记--Servlet代码集

登录系统
 提交表单数据
 打开PDF
Cookie
URL传递参数
 URL重写跟踪会话
 使用HttpSession对象跟踪会话
 Servlet间协作
 过滤器Filter

登录系统

<!DOCTYPE HTML PUBLIC "=//w3c//dtd html 4.0 transitional/cn">

<html>

  <head>

    <title>提交表单数据</title>

  </head>

  <body bgcolor="#FFFFFF">

  <h1 align="center"><b>欢迎登陆系统</b></h1>

  <form action = "servlet/GetPostData" method = "post">

  <p></p>

  	<table width = "52%"border="2" align ="center">

  		<tr bgcolor ="#FFFFCC">

	  		<td align = "center" width="43%"><div align="center">用户名：</div></td>

	  		<td width="57%">

	  		<div align="left">

	  			<input type ="text" name = "username">

	  		</div>

	  		</td>

  		</tr>

  		<tr bgcolor = "#ccff99">

	  		<td align = "center" width = "43%">

		  		<div align= "center">密码:</div>

		  	</td>

		  	<td width = "57%">

		  		<div align = left>

		  			<input type="password" name= "password">

		  		</div>

	  		</td>

  		</tr>

  		</table>

  		<p align="center">

  		<input type="reset" name= "Reset" value = "重置">

  		<input type="submit" name= "Submit2" value = "提交">

  </form>

  </body>

</html>

GetPostData.java

protected void processRequest(HttpServletRequest req,HttpServletResponse resp)

		throws ServletException,IOException{

		 resp.setContentType("text/html;charset=gb2312"); //确保汉字信息正确编码方式显示

		 req.setCharacterEncoding("gb2312");//确保参数信息以汉字编码方式提取

		 PrintWriter myout = resp.getWriter();

		 myout.println(

				 "<html>"+

				 "<head></head>"+

				 "<body bgcolor=\"#FDF5E6\">\n"+

				 "<h1 align=center>"+"get post data" + "</h1>\n"+

				 "<ul>\n"+

				 "<li><b>username</b>:"+

				 req.getParameter("username")+"\n"+

				 "<li><b>password</b>:"+

				 req.getParameter("password")+"\n"+

				 "</ul>\n"+

				 "</body></html>"

				 );

		 myout.close();

	}

	protected void doGet(HttpServletRequest req,HttpServletResponse resp)

		throws ServletException,IOException{

		processRequest(req,resp);

	}

	protected void doPost(HttpServletRequest req,HttpServletResponse resp)

			throws ServletException,IOException{

		processRequest(req,resp);

	}

============================================================

提交表单数据

<!DOCTYPE HTML PUBLIC "=//w3c//dtd html 4.0 transitional/cn">

<html>

  <head>

    <title>提交表单数据</title>

  </head>

  <body bgcolor="#FFFFFF">

	  <h1 align="center"><b>选择你喜欢的蔬菜</b></h1>

	  <form action="servlet/GetPostData" method="post">

		  <input type="checkbox" name="vegatablebox" value="Cucumber">黄瓜

		  <input type="checkbox" name="vegatablebox" value="Tomato">西红柿

		  <input type="checkbox" name="vegatablebox" value="Potato">土豆

		  <ul></ul>

		  <input type="reset" name="Reset" value="重置">

		  <input type="submit" name="Submit" value="提交">

	  </form>

  </body>

</html>

GetPostData.java

protected void processRequest(HttpServletRequest request, HttpServletResponse response)

			throws ServletException,IOException{

		response.setContentType("text/html;charset=gb2312"); //确保汉字信息正确编码方式显示

		request.setCharacterEncoding("gb2312");//确保参数信息以汉字编码方式提取

		String[] paramValues = request.getParameterValues("vegatablebox");

		PrintWriter out = response.getWriter();

		out.print(

				"<html>"+

				"<head><title>喜欢的蔬菜</title></head>"+

				"</body>"+

				"你喜欢的蔬菜是：");

		for(int vnum = 0 ; vnum < paramValues.length ; vnum++){

			out.print(paramValues[vnum]+" ");

		}

		out.print(

				"</body></html>"

				);

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

============================================================

打开PDF

public void pdfInfo(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		response.setContentType("application/pdf");

		ServletOutputStream out = response.getOutputStream();

		//response.setHeader("Content-disposition", "attachment;filename=sample.pdf");

		//不在网页中直接显示，而是下载

		File pdf = null;

		BufferedInputStream buf = null;

		try{

			pdf=new File("f:\\sample.pdf");

			response.setContentLength((int)pdf.length());

			FileInputStream input = new FileInputStream(pdf);

			buf = new BufferedInputStream(input);

			int readBytes=0;

			while((readBytes=buf.read())!=-1)

				out.write(readBytes);

		}catch(IOException e){

			out.println("File not found!");

		}finally{

			if(out!=null){

				out.close();

			}if(buf!=null)

				buf.close();

		}

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		pdfInfo( request,  response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		pdfInfo( request,  response);

	}

============================================================

public void processRequest(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		Cookie cookie = null;

		//获取请求相关的Cookie

		Cookie[] cookies = request.getCookies();

		//判断Cookie ServletStudy是否存在,若存在，数值+1

		/*if(cookies!= null){

			for(int i = 0 ; i <cookies.length ; i ++){

				if(cookies[i].getName().equals("VisitTimes")){

					String v = cookies[i].getValue();

					int value = Integer.parseInt(v)+1;

					cookies[i].setValue(Integer.toString(value));

					//将值更新后的cookie重新写回响应

					response.addCookie(cookies[i]);

					cookie=cookies[i];

				}

			}

		}//end if

		*/

		if(cookies!= null){

			for(int i = 0 ; i <cookies.length ; i ++){

				if(cookies[i].getName().equals("VisitTimes")){

					cookie=cookies[i];

					break;

				}

			}

		}//end if

		if(cookie == null){

			int maxAge=-1;

			//创建Cookie对象

			cookie=new Cookie("VisitTimes","1");

			cookie.setPath(request.getContextPath());

			cookie.setMaxAge(maxAge);

			response.addCookie(cookie);

		}//end if

		else{

			//定义一个存放次数的变量

			int count = 0;

			//通过getValue()方法得到从客户端myCookie的值,得到的值是一个String类型的要将转换成int类型的,才能进行计数操作

			count = Integer.parseInt(cookie.getValue());

			//累加访问的次数

			count++;

			//把count的值添加到定义的Cookie对象中

			cookie.setValue(String.valueOf(count));

			//设置Cookie的最大保存时间

			//cookie.setMaxAge(60 * 60 * 24 * 30);

			//把Cookie添加到客户端

			response.addCookie(cookie);

		}

		//显示信息

		response.setContentType("text/html;charset=gb2312"); //确保汉字信息正确编码方式显示

		response.setCharacterEncoding("gb2312");//确保参数信息以汉字编码方式提取

		PrintWriter out = response.getWriter();

		out.println("<html>");

		out.println("<head>");

		out.println("<title>Cookie 跟踪会话</title>");

		out.println("</head>");

		out.println("<body>");

		out.println("<h2>您好！</h2>");

		out.println("欢迎您"+cookie.getValue()+"访问本页面<br>");

		out.println("</body>");

		out.println("</html>");

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

============================================================

URL传递参数

URLRewrite.java

public void processRequest(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		response.setContentType("text/html,charset=GB2312");

		response.setCharacterEncoding("gb2312");//确保参数信息以汉字编码方式提取

		PrintWriter out = response.getWriter();

		String contextPath = request.getContextPath();

		String encodedUrl = response.encodeURL(contextPath+

				"/servlet/URLRewriteServer?name=张三&age=27");

		out.println("<html>");

		out.println("<head>");

		out.println("<title>URL Rewriter</title>");

		out.println("</head>");

		out.println("<body>");

		out.println("<h1>URL重写演示：发送参数</h1>");

		out.println("转到URL2<a href=\""+encodedUrl+"\">here</a>");

		out.println("</body>");

		out.println("</html>");

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

　URLRewriteServer.java

public void processRequest(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		response.setContentType("text/html,charset=GB2312");

		response.setCharacterEncoding("gb2312");//确保参数信息以汉字编码方式提取

		PrintWriter out = response.getWriter();

		out.println("<html>");

		out.println("<head>");

		out.println("<title>URL Rewriter</title>");

		out.println("</head>");

		out.println("<body>");

		out.println("<h1>URL重写演示：接收参数</h1>");

		out.println("下面是接收的参数:<br>");

		String paramname= request.getParameter("name");

		String x = new String(paramname.getBytes("ISO-8859-1"), "GBK");

		//直接显示汉字会导致乱码，所以先转换为GBK

		//out.println("name="+request.getParameter("name"));

		out.println(x);

		out.println("age="+request.getParameter("age"));

		out.println("</body>");

		out.println("</html>");

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

　　注意

String paramname= request.getParameter("name");

String x = new String(paramname.getBytes("ISO-8859-1"), "GBK");

        //直接显示汉字会导致乱码，所以先转换为GBK

============================================================

URL重写跟踪会话

URLRewrite.java

public class URLRewrite extends HttpServlet {

	public void processRequest(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		response.setContentType("text/html,charset=GB2312");

		response.setCharacterEncoding("gb2312");//确保参数信息以汉字编码方式提取

		PrintWriter out = response.getWriter();

		String contextPath = request.getContextPath();

		String encodedUrl = response.encodeURL(contextPath+

				"/servlet/URLRewriteServer?name=张三&age=27");

		out.println("<html>");

		out.println("<head>");

		out.println("<title>URL Rewriter</title>");

		out.println("</head>");

		out.println("<body>");

		out.println("<h1>URL重写演示：发送参数</h1>");

		out.println("转到URL2<a href=\""+encodedUrl+"\">here</a>");

		out.println("</body>");

		out.println("</html>");

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

}

URLRewriteServer.java

public class URLRewriteServer extends HttpServlet {

	public void processRequest(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		response.setContentType("text/html,charset=GB2312");

		response.setCharacterEncoding("gb2312");//确保参数信息以汉字编码方式提取

		PrintWriter out = response.getWriter();

		out.println("<html>");

		out.println("<head>");

		out.println("<title>URL Rewriter</title>");

		out.println("</head>");

		out.println("<body>");

		out.println("<h1>URL重写演示：接收参数</h1>");

		out.println("下面是接收的参数:<br>");

		String paramname= request.getParameter("name");

		String x = new String(paramname.getBytes("ISO-8859-1"), "GBK");

		//直接显示汉字会导致乱码，所以先转换为GBK

		//out.println("name="+request.getParameter("name"));

		out.println(x);

		out.println("age="+request.getParameter("age"));

		out.println("</body>");

		out.println("</html>");

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

}

============================================================

使用HttpSession对象跟踪会话

HitCounter.java

public class HitCounter extends HttpServlet {

	static final String COUNTER_KEY="Counter";

	protected void processRequest(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		//获取会话对象

		HttpSession session = request.getSession(true);

		response.setContentType("text/html;charset=GB2312");

		response.setCharacterEncoding("gb2312");//确保参数信息以汉字编码方式提取

		PrintWriter out = response.getWriter();

		//从会话中获取属性

		int count =1;

		Integer i = (Integer)session.getAttribute(COUNTER_KEY);

		//如果存在以前的数值

		if(i!=null){

			count=i.intValue()+1;

		}

		//将属性信息存入会话

		session.setAttribute(COUNTER_KEY, new Integer(count));

		Date lastAccessed = new Date(session.getLastAccessedTime());

		Date sessionCreated = new Date(session.getCreationTime());

		DateFormat formatter = DateFormat.getDateTimeInstance(DateFormat.MEDIUM,DateFormat.MEDIUM);

		//输出对话信息

		out.println("<html>");

		out.println("<head>");

		out.println("<title>会话计数器</title>");

		out.println("</head>");

		out.println("<body>");

		out.println("你的会话ID:<b>"+session.getId()+"<br>");

		out.println("会话创建时间："+formatter.format(sessionCreated)+"<br>");

		out.println("会话上次访问时间："+formatter.format(lastAccessed)+"<br>");

		out.println("</b>会话期间你向页面发起<b>"+count+"</b>次请求");

		out.println("<form method=GET action=\""+request.getRequestURI()+"\">");

		out.println("<input type='submit'"+"value=\"再次点击...\">");

		out.println("</form>");

		out.println("</body>");

		out.println("</html>");

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

}

============================================================

Servlet间协作

Main.java

public class Main extends HttpServlet {

	public void processRequest(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		String m_userID = request.getParameter("userID");

		if(m_userID==null) m_userID="";

		String m_password = request.getParameter("password");

		if(m_password==null) m_password="";

		if(m_userID.equals("guest")&&m_password.equals("guest")){

			RequestDispatcher dispatcher =request.getRequestDispatcher("/servlet/LoginSuccess");

			dispatcher.forward(request,response);

			//RequestDispatcher.forward()方法

			//将当前的request和response重定向到该 RequestDispacher指定的资源。

		}else{

			RequestDispatcher dispatcher =request.getRequestDispatcher("/servlet/LoginFail");

			dispatcher.forward(request,response);

		}

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

}

LoginSuccess.java

public class LoginSuccess extends HttpServlet {

	public void processRequest(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		response.setContentType("text/html;charset=GB2312");

		response.setCharacterEncoding("gb2312");

		PrintWriter out = response.getWriter();

		String name = request.getParameter("userID");

		out.println("<html>");

		out.println("<head>");

		out.println("<title>登录成功</title>");

		out.println("</head>");

		out.println("<body>");

		out.println("<h1>欢迎！"+name+ "您已成功登录系统...</h1>");

		out.println("</body>");

		out.println("</html>");

		out.close();

	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		processRequest(request,response);

	}

}

LoginFail.java

代码和LoginSuccess.java类似，只改了汉字

dl.html

<!DOCTYPE HTML PUBLIC "=//w3c//dtd html 4.0 transitional/cn">

<html lang='zh'>

  <head>

    <title>登录</title>

  </head>

  <h1 align="center"><b>欢迎登陆系统</b></h1>

  <form name="login" method = "post" action="servlet/Main">

　　<div align="center">用户名：</div>

　　<input type ="text" name = "userID" value="">

　　<div align= "center">密码:</div>

　　<input type="password" name= "password" value="">

　　<input type="reset" name= "reset" value = "重置">

　　<input type="submit" name= "tj" value = "提交">

  </form>

  </body>

</html>

============================================================

过滤器Filter

在上一部分的程序基础上加上

TimeTrackerFilter.java

public class TimeTrackFilter implements Filter {

	private FilterConfig filterConfig=null;

	public void destroy() {

		this.filterConfig=null;

	}

	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

			throws IOException, ServletException {

		Date startTime , endTime;

		double totalTime;

		StringWriter sw = new StringWriter();

		System.out.println("我在Filter中");

		try{

			Thread.sleep(2000);

		}catch(InterruptedException e){

			System.out.println(e.toString());

		}

		startTime = new Date();

		chain.doFilter(request, response);

		endTime = new Date();

		totalTime = endTime.getTime()- startTime.getTime();

		System.out.println("我在Filter中");

		PrintWriter writer = new PrintWriter(sw);

		writer.println("==============");

		writer.println("耗时"+totalTime+"毫秒");

		writer.println("==============");

		filterConfig.getServletContext().log(sw.getBuffer().toString());

	}

	public void init(FilterConfig fConfig) throws ServletException {

		this.filterConfig=fConfig;

	}

}

　　需要完成destory() init() doFilter() 三个函数

其余效果均与上一个程序相同，在服务器控制台会有如下显示

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