|
|
Adding dynamic content via expressions
As we saw in the previous section, any HTML file can be turned into a JSP file
by changing its extension to .jsp. Of course, what makes JSP useful is the
ability to embed Java. Put the following text in a file with .jsp
extension (let us call it hello.jsp), place it in your JSP directory, and view
it in a browser.
<HTML>
<BODY>
Hello! The time is now <%= new java.util.Date() %>
</BODY>
</HTML>
Notice that each time you reload the page in the browser, it comes up with the
current time.
The character sequences <%= and %> enclose Java expressions, which are
evaluated at run time.
This is what makes it possible to use JSP to generate dyamic HTML pages that
change in response to user actions or vary from user to user.
Exercise: Write a JSP to output the values returned by System.getProperty for
various system properties such as java.version, java.home, os.name,
user.name, user.home, user.dir etc. |