原理：设置 web.xml，使 Servlet 在项目启动时自动创建对象，各用户访问 Servlet 可实现在 Servlet 下的对象共享，再通过 Session 可将 JSP 也实现对象共享。
将要共享的对象 ShareInfo.java
/**
*
*/
package test;
/**
* @author Administrator
*
*/
public class ShareInfo
{
private int val = 0;
/**
*
*/
public ShareInfo()
{
// TODO Auto-generated constructor stub
}
/**
* 累加
*/
public void add()
{
val = val + 1;
}
/**
* 取值
*
* @return
*/
public int getVal()
{
return val;
}
}
启动时加载的 Servlet
package servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import test.ShareInfo;
/**
* Servlet implementation class Info
*/
@WebServlet(name = "info", urlPatterns = { "/info" })
public class Info extends HttpServlet
{
private static final long serialVersionUID = 1L;
// 声明共享对象
private ShareInfo shareInfo = null;
/**
* @see HttpServlet#HttpServlet()
*/
public Info()
{
super();
// TODO Auto-generated constructor stub
}
/**
* @see Servlet#init(ServletConfig)
*/
public void init(ServletConfig config) throws ServletException
{
// TODO Auto-generated method stub
// 创建共享对象
shareInfo = new ShareInfo();
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
// TODO Auto-generated method stub
doPost(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
// TODO Auto-generated method stub
// 对象得到共享
// 对象内数字累加
shareInfo.add();
// 存入 session,jsp 页面也将获得共享
HttpSession httpSession = request.getSession();
httpSession.setAttribute("INFO", shareInfo);
processRequest(String.valueOf(shareInfo.getVal()), request, response);
}
/**
* return text to explorer
*
* @param strMessage
* @param request
* @param response
* @throws ServletException
* @throws IOException
*/
protected void processRequest(String strMessage, HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try
{
out.print(strMessage);
}
finally
{
out.close();
}
}
}
设置启动 Servlet 的 web.xml
<servlet> <servlet-name>Info</servlet-name> <servlet-class>servlet.Info</servlet-class> <load-on-startup>1</load-on-startup> </servlet>
获得共享的 jsp
<%@page import="test.ShareInfo"%>
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@ page import="test.ShareInfo"%>
<%
ShareInfo shareInfo = null;
Object object = session.getAttribute("INFO");
if (object != null)
{
shareInfo = (ShareInfo) object;
shareInfo.add();
}
else
{
out.print("没有找到对象，用户需要访问一次 servlet 获取 session 赋值");
return;
}
%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>GlassFish JSP Page</title>
</head>
<body>
<%=shareInfo.getVal()%>
</body>
</html>
源码下载
http://download.csdn.net/detail/joyous/5345508
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