ssession和servletContext的比较

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servlet

Servlet Java Access HTML

Servlet实现访问次数的例子

//ShowTimesServlet.java /*Servlet实现访问次数的例子!*/
import java.io.*;
import java.util.zip.*;
import javax.servlet.*;
import javax.servlet.http.*;
/*
 这个类实现访问次数。显示访问次数！看是第几次访问！
*/
public class ShowTimesServlet extends HttpServlet {

 public void doGet(HttpServletRequest request,HttpServletResponse response)
               throws ServletException, java.io.IOException {

            response.setContentType("text/html");
   HttpSession session = request.getSession();
   String heading;
   Integer accessCount =(Integer)session.getAttribute("accessCount");
   if(accessCount == null) {
    accessCount = new Integer(0);
    heading = "Welcom,You are first time to visit!";
   }
   else {
    heading = "Welcome Backer";
    accessCount = new Integer(accessCount.intValue()+1);
   }
      session.setAttribute("accessCount",accessCount);
   PrintWriter out = response.getWriter();
   out.println("The title:"+heading);
   out.println("Access count: "+accessCount);
 }

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

}

下面是通过servleContext来做访问次数

package org.linweihan.test;

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 TestServletContext extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		ServletContext servletContext = this.getServletContext();
		Integer accessCount =(Integer)servletContext.getAttribute("accessCount");
		if(accessCount == null){
			accessCount = 0;
		}else{
			accessCount = accessCount + 1;
			
		}
		servletContext.setAttribute("accessCount", accessCount);
		PrintWriter out = response.getWriter();
		out.println("<html><body><h2>"+accessCount+"</body></html>");
	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
	}
	


}

区别在于session是局部的,servletContext是共享的.
当换了另一个窗口开始访问又从0开始计数,而servletContext则是接下去计数.

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