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The moose likes Web Component Certification (SCWCD/OCPJWCD) and the fly likes Using jsp:useBean without class attribute Big Moose Saloon
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Using jsp:useBean without class attribute

pal sahab

Joined: Feb 11, 2009
Posts: 8
This is to reference to BE THE CONTAINERON page # 358 in HF SCWCD book.


<jsp:useBean id="person" type="foo.Employee" scope="request" >
<jsp:setProperty name="person" property="name" value="Fred" />
Name is : <jsp:getProperty name="person" property="name" />

1. What happens if the servlet code looks like:

foo.Person p = new foo.Person();

Where Person is abstract class and Employee extends Person and is concreate class.

Explanation given :

Fails at request time.The "person" attribute is stored at request scope,so the <jsp:useBean> tag won`t work since it specifies only a type.The CONTAINER knows that if you have only a type specified ,there must be an existing bean attribute of the name and scope.

My Doubt

According to my understanding if the attribute ("person") is already in request scope then the <jsp:useBean> will try to find the attribute by something like this in generated _jspService method by the container.

person = (foo.Employee)_jspx_page_context.getAttribute("person",PageContext.Request_Scope);

so if person if not null then there is no point of failure at request time and <jsp:getProperty> will print the name.

Can anybody please explain where iam wrong?

Sumit Kumar
Ankit Garg

Joined: Aug 03, 2008
Posts: 9293

This is an error in the book, checkout the errata to know about this and other errors in the book...

SCJP 6 | SCWCD 5 | Javaranch SCJP FAQ | SCWCD Links
pal sahab

Joined: Feb 11, 2009
Posts: 8
Thank you Ankit
jQuery in Action, 2nd edition
subject: Using jsp:useBean without class attribute