java在Servlet中存取Session，servletsession,下面例子演示如何在Htt
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java在Servlet中存取Session，servletsession,下面例子演示如何在Htt
下面例子演示如何在HttpServlet中存取Session。 Session实例可以通过HttpServletRequest的getSession()方法获得，此方法会返回一个布尔值来表示是否成功得到了Session。
然后我们尝试获得键名为“VisitCounter”的session值，然后将获得的值转换为Integer对象。 如果是空则说明session还没有设置，就往session中添加VisitCounter。否认则对VisitCounter+1并保存到session中。
import java.io.*;import javax.servlet.*;import javax.servlet.http.*;/** * Example Servlet * @author byrx.net */public class ExampleServlet extends HttpServlet { /** Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods. * @param request servlet request * @param response servlet response */ protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); printPageStart(out); //Obtain the session object, create a new session if doesn't exist HttpSession session = request.getSession(true); //Check if our session variable is set, if so, get the session variable value //which is an Integer object, and add one to the value. //If the value is not set, create an Integer object with the default value 1. //Add the variable to the session overwriting any possible present values. Integer param = (Integer) session.getAttribute("MySessionVariable"); if (param != null) { session.setAttribute("MySessionVariable", new Integer(param.intValue() + 1)); param = (Integer) session.getAttribute("MySessionVariable"); } else { param = new Integer(1); session.setAttribute("MySessionVariable", param); } out.println("You have displayed this page <b>" + param.intValue() + "</b> times this session.<br/><br/>"); out.println("Hit the browsers refresh button."); printPageEnd(out); } /** Prints out the start of the html page * @param out the PrintWriter object */ private void printPageStart(PrintWriter out) { out.println("<html>"); out.println("<head>"); out.println("<title>Example Servlet of how to store and retrieve session variables</title>"); out.println("</head>"); out.println("<body>"); } /** Prints out the end of the html page * @param out the PrintWriter object */ private void printPageEnd(PrintWriter out) { out.println("</body>"); out.println("</html>"); out.close(); }}
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