JavaEE---Servlet会话跟踪之SessionContext

最新推荐文章于 2024-12-02 11:16:08 发布

原创最新推荐文章于 2024-12-02 11:16:08 发布 · 779 阅读

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本文详细介绍了JavaWeb程序设计中如何通过Servlet实现用户数量的实时统计，并在页面上进行展示。包括如何获取ServletContext，使用线程同步确保数据一致性，以及设置响应类型和内容。

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参考自《Java Web程序设计》

package servlet;

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

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 IndexServlet extends HttpServlet {
	public IndexServlet() {
		super();
	}
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		ServletContext ctx = this.getServletContext();//如何获得，与获得Session的区别
		synchronized (this){
			Integer counter = (Integer) ctx.getAttribute("UserNumber");
			int tmp = 0;
			if(counter == null){
				counter = new Integer(1);
			}else{
				tmp = counter.intValue() + 1;
				counter = new Integer(tmp);
			}
			ctx.setAttribute("UserNumber", counter);
		}
		response.setContentType("text/html;charset=GBK");
		PrintWriter out = response.getWriter();
		out.println("<h1>这是第一页</h1>");
		out.println("<a href='UserNumber'>人数统计</a>");//相对地址
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doGet(request,response);
	}
	public void init() throws ServletException {
		// Put your code here
	}

}

package servlet;

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

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 UserNumber extends HttpServlet {
	public UserNumber() {
		super();
	}
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
        ServletContext ctx = this.getServletContext();
        Integer counter = (Integer)ctx.getAttribute("UserNumber");
        response.setContentType("text/html;charset=GBK");
        PrintWriter out = response.getWriter();
        if(counter != null){
        	out.println("已经有"+counter.intValue()+"人访问过该网站");
        }else{
        	out.println("你是第一个访问该网站的人");
        }
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
         doGet(request,response);
	}
	public void init() throws ServletException {
		// Put your code here
	}

}