Struts and Scope
The
Struts framework uses various shared resource areas to store objects.
The shared resource areas all have a lifetime and visibility rule
that defines the scope
of the resource. This
section discusses these resources, their scopes, and how the
framework uses them.
Request Scope
Each time a client issues an HTTP
request, the server creates an object that implements the
javax.servlet.http.HttpServletRequest
interface. Among other things, this
object contains a collection of key/value attribute pairs that can be
used to store objects for the lifetime of the request. The key of
each pair is a String
, and the value can be any
type of Object
. The methods to store objects in
and retrieve them from the request scope are:
public void setAttribute( String name, Object obj ); public Object getAttribute( String name );
Request-scope attributes can be removed
using the removeAttribute( )
method; however,
because the scope of the attribute is only for the lifetime of the
request, it is not as important to remove them as it is for other
scoped attributes. Once the server fulfills a request and a response
is returned to the client, the request and its attributes are no
longer available to the client and may be garbage-collected by the
JVM.
The Struts framework provides the ability to store JavaBeans in a request, so that they can be used by presentation components such as JSP pages. This makes it much easier to access JavaBeans data, without having to do a manual cleanup ...
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