ssession和servletContext的比较
Servlet实现访问次数的例子
下面是通过servleContext来做访问次数
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.
//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.