图例展示:
在一次调教刷新之后:
源码示例:
@WebServlet("/scope")
public class ScopeServlet extends HttpServlet {
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//request:
Integer numInRequest=(Integer) req.getAttribute("NUM_IN_REQUEST");
if (numInRequest==null) {
req.setAttribute("NUM_IN_REQUEST", 1);
} else {
req.setAttribute("NUM_IN_REQUEST", numInRequest+2);
}
//--------------------------------------------------------------
//session:
Integer numsession= (Integer)req.getSession().getAttribute("NUM_IN_SESSION");
if (numsession==null) {
req.getSession().setAttribute("NUM_IN_SESSION", 1);
} else {
req.getSession().setAttribute("NUM_IN_SESSION", numsession+1);
}
//--------------------------------------------------------------
//application:
Integer numapp=(Integer)req.getServletContext().getAttribute("NUM_IN_APP");
if (numapp==null) {
req.getServletContext().setAttribute("NUM_IN_APP", 1);
} else {
req.getServletContext().setAttribute("NUM_IN_APP", numapp+3);
}
//--------------------------------------------------------------
req.getRequestDispatcher("/result").forward(req, resp);
}
}
=======================================================================================
@WebServlet("/result")
public class ResultServlet extends HttpServlet{
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setContentType("text/html;charset=utf-8");
PrintWriter out=resp.getWriter();
//request============================================================================
Integer numreuqest=(Integer)req.getAttribute("NUM_IN_REQUEST");
out.println("numreuqest="+numreuqest);
//session============================================================================
Integer numsession=(Integer)req.getSession().getAttribute("NUM_IN_SESSION");
out.println("<br>numsession="+numsession);
//application=============================================================================
Integer numapp=(Integer)req.getServletContext().getAttribute("NUM_IN_APP");
out.println("<br>numapp="+numapp);
}
}