required
Defines if the nesting attribute is required or optional.
The syntax is:
required
    (#PCDATA) >
#PCDATA ::= true | false | yes | no
If not present then the default is  false , i.e the attribute is optional.
rtexprvalue
Defines if the nesting attribute can have scriptlet expressions as a value, i.e the value of the 
attribute may be dynamically calculated at request time, as opposed to a static value 
determined at translation time.
The syntax is:
rtexprvalue
 (#PCDATA) >
#PCDATA ::= true | false | yes | no
If not present then the default is  false , i.e the attribute has a static value
5.4
Tag Handlers
A 
tag handler
 is a run time server side object that is created to help evaluate actions during 
the execution of a JSP page. A tag handler supports a run time protocol that facilitates 
passing information from the JSP page to the handler.
A tag handler is a server side invisible JavaBeans component, but it implements an 
additional interface to indicate that it has a richer run time protocol. There are two interfaces 
that describe a tag handler: 
Tag
 is used for simple tag handlers that are not interested in 
manipulating their body content (if any); 
BodyTag
 is an extension of 
Tag
 and gives a tag 
handler access to its body.  The 
TagSupport
 and 
BodyTagSupport
 classes can be used 
as base classes when creating new tag handlers.
5.4.1
Properties
A tag handler has some 
properties
 that are set by the JSP container (usually through the JSP 
page implementation class) using setter methods:
Chapter 5
Tag Extensions
100




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