Servlet数据成员保持会话？

2 回答

• 3

  Servlet - 因此它们的数据成员 - 在服务器上的所有会话之间共享 . 从而

  当具有相同会话的同一用户被定向到包含该类的servlet时，它将保留其数据还是每次都重新生成？

  数据将保留（对所有用户），直到您重新启动Web应用程序 .

  每个用户/会话是否都有该成员的不同副本或是否共享？

  它是共享的 .

  如果servlet中的数据成员不保持同一会话的状态，那么您建议什么？也许激活地将它添加到会话中？

  会话特定数据应存储在 HttpSession 中 .

  回复于 2024-04-25T21:41:27+08:00
• 0

  为了确保这种行为，我写了一点 TestingServlet - 我将向您展示servlet及其成员的生命周期 . 还提供;如何使用会话变量

  import java.io.IOException;
  import java.io.PrintWriter;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  /**
   * Basic servlet for lifecycle testing
   * 
   * @author powermicha
   * 
   */
  public class TestingServlet extends HttpServlet {
  
      /**
       * 
       */
      private static final long serialVersionUID = 4020575563844924588L;
  
      private Logger logger;
  
      private int requestCounter;
  
      @Override
      public void init() throws ServletException {
          logger = Logger.getLogger("TestingServlet_" + System.currentTimeMillis());
          logger.log(Level.INFO, "TestingServlet initialized");
  
          requestCounter = 0;
      }
  
      @Override
      public void destroy() {
          logger.log(Level.INFO, "TestingServlet destroyed");
      }
  
      @Override
      protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  
          int requestsPerSession = incrementRequestsPerSession(req);
  
          String logMessage = "TestingServlet was called " + (++requestCounter) + " times. " 
                  + requestsPerSession + " times from the same session (ID:"
                  + req.getSession().getId() + ")";
  
          logger.log(Level.INFO, logMessage);
  
          // send it to the browser
          PrintWriter writer = resp.getWriter();
          writer.write(logMessage);
          writer.close();
      }
  
      private int incrementRequestsPerSession(HttpServletRequest req) {
  
          Integer counter = (Integer) req.getSession().getAttribute("requestsPerSession");
          if (counter == null) {
              counter = 1;
          } else {
              counter++;
          }
  
          req.getSession().setAttribute("requestsPerSession", counter);
  
          return counter;
      }
  
  }
  

  回复于 2024-04-25T21:41:27+08:00