page is instanceof JspPage

[Himai Minh]

According to Niko's mock exam, this code return true.

 
<%= page instanceof JspPage%>

But page is an instanceof an Object. Why this is still true?
Thanks.

[Paul Clapham]

Himai Minh wrote:But page is an instanceof an Object.

Why is that a relevant statement? Every Java object is an instance of Object.

[Himai Minh]

Hi, Paul,
But according to this web site: http://beginnersbook.com/2013/11/jsp-implicit-objects/ and p. 298 of Head First book
page is an instance of Object.

[Paul Clapham]

Okay. And is JspPage a class? Because that's what the table you linked to is talking about. My 30 seconds of web searching tends to suggest to me that it's an interface.

[Himai Minh]

Hi, I know why page is an Object and also an instance of JspPage.
On p. 297 of Head First,
A JSP is translated into:

public final class BasicCounter_jsp extends ... HttpJspBase implements ...
{


public void _jspService( ...) {
   ...
   Object page = this;
....
}
}

page is an instance of an Object of this BasicCounter_jsp. BasicCounter_jsp is an instance of HttpJspBase. HttpJspBase implements HttpJspPage, which implements JspPage.