ServletContextDemo

1、servlet 之间共享数据

package xw.servlet;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * 演示向Servletcontext中保存数据
 *
 */
public class AServletContext extends HttpServlet {

    /*
     * 1. 获取ServletContext对象
     * 2. 调用其setAttribute()方法完成保存数据
     */    

    public void doGet(HttpServletRequest request, HttpServletResponse response){
        ServletContext servletContext=this.getServletContext();
        servletContext.setAttribute("name","zhangsan");
    }
}

package xw.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;
/**
 * 演示从ServletContext中获取数据
 */
public class BServletContext extends HttpServlet {
    /*
     * 1. 获取ServletContext对象
     * 2. 调用其getAttribute()方法完成获取数据
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        ServletContext servletContext=this.getServletContext();
        System.out.println(servletContext.getAttribute("name"));
    }
}

先运行AServletContext  再运行 BServletContext

2、ServletContext 统计页面访问量

package xw.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;
/**
 * 统计访问量
 */
public class CServletContext extends HttpServlet {

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

        /*
         * 1. 获取ServletContext对象
         * 2. 从ServletContext对象中获取名为count的属性
         *   3. 如果存在：给访问量加1，然后再保存回去；
         *   4. 如果不存在：说明是第一次访问，向Servletcontext中保存名为count的属性，值为1
         */
        ServletContext app = this.getServletContext();
        Integer count = (Integer)app.getAttribute("count");
        if(count == null) {
            app.setAttribute("count", );
        } else {
            app.setAttribute("count", count+);
        }

        /*
         * 向浏览器输出
         *   需要使用响应对象！
         */
        PrintWriter pw = response.getWriter();
        pw.print("<h1>" + count + "</h1>");
    }

}

访问路径，显示效果如下：

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" 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