problem in understanding jstl set tag

HF page 446

"In the <c:set> tag, the target attribute in the tag seems like it should work just like "id" in the <jsp:setProperty>, but it doesn't work that way"

But there is no "id" in <jsp:setProperty" . Is it talking about <jsp:useBean>

"With the target attribute, you do not type in a String literal that represents the name under which the attribute was bound to page,scope etc"

What does this mean?

I tried the following

Person.java

JSP

This does work fine. But i am using the "id" in <jsp:useBean> And if it really is <jsp:useBean> above instead of <jsp:setProperty> , how does this work.
Also What are the other ways in which a bean can be created and given as a value to "target"

Page 447 6th Bullet point

If you put in a String literal that represents the "id" name of the bean or Map, it won't work. In other words , "target" is not for the attribute name of the bean or Map-its for the actual attribute object.

What is the difference between attribute object and attribute name

if I say

<% com.Person p = new com.Person();
request.setAttribute("person", p);
%>

then in this case is "person" a attribute name or object? I think it's a name which represents an object p.
Then how can we differentiate between the two.
Moreover on the next page to which the request is submitted I only have access to "person", I can't get "p" directly.

Plz help me understand this.

You are right.

The id in <jsp:setProperty> is the <jsp:useBean> 'id'. The <c:set> target attribute does not allow a string literal "person". If it did allow the string literal, then how would the <c:set> know that the author of the JSP page really wanted a 'person object' and not string literal "person" string.

Attributes have names and values. The name is a key, similar to Map keys, and the value is a java.lang.Object. "person", in your example, is the Attribute name, and the object referenced by "p" is the Attribute value.

About your question about the difference between attribute object and attribute name.

What you object (or instance, call it the way you like) is is really just no more than a chunk of data stored on the heap. This is what you create when you type new com.Person().

In your code, you decided to store this object in a local variable you called p. One line later, you put the content of the p variable into your request attributes collection (yes, you can think of this as a java.util.Map). So there is really no reason you can get a direct acces to you p variable by any other mean than a scriptlet (remember that all scriptlets of the page are put into the same and unique method when you JSP is translated).

In fact, you could have written something like this: