The application| variable application variable is a valid global variable for a Web application and is useful for saving some globally valid values. Unlike session variables, application variables can be accessed using Application.getattribute () and Application.setattribute ().
In JSP, you can automatically reference the application variable, referring to the current Web application. (For Web applications, I'll discuss them in another place.) ）
When referencing a application variable, you must use synchronization. Also, you need to test whether a application property already exists. Please study the following code, set a application property called "Change" below, and save an integer value. With respect to using application variables in a servlet, the method is consistent with the following code, however, you need to first describe a application as follows:
ServletContext Application=getservletcontext ();
The following function is a fragment of env.java that can be used to see how to use Application variables in a servlet.
Integer count = null;
Synchronized (application) {
Count = (Integer) application.getattribute ("Change");
if (count = null)
Count = new Integer (0);
Count = new Integer (Count.intvalue () + 1);
Application.setattribute ("Change", count);
}
private void Printapplication (PrintWriter pw, httpservletrequest req)
Throws IOException
{
ServletContext application = Getservletcontext ();
Pw.println ("
Pw.println ("<table>");
Pw.print ("<tr><td>major version<td>");
Pw.println (Application.getmajorversion ());
Pw.print ("<tr><td>minor version<td>");
Pw.println (Application.getminorversion ());
Pw.print ("<tr><td>server info<td>");
Pw.println (Application.getserverinfo ());
Pw.print ("<tr><td>real Path (of PathInfo) <td>");
Pw.println (Application.getrealpath (Req.getpathinfo ()));
Pw.print ("<tr><td>mime-type (of PathInfo) <td>");
Pw.println (Application.getmimetype (Req.getpathinfo ()));
Pw.println ("</table>");
Pw.println ("
Pw.println ("<table>");
Enumeration E = Application.getattributenames ();
while (E.hasmoreelements ()) {
String name = (string) e.nextelement ();
Pw.print ("<tr><td>");
Pw.print (name);
Pw.print ("<td>");
Pw.println (Application.getattribute (name));
}
Pw.println ("</table>");
}
%>
<body bgcolor= #ffffff >
</body>
