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From bugzi...@apache.org
Subject DO NOT REPLY [Bug 33190] New: - Facility for passing an Iterator object into the 'View' part of an MVC framework
Date Fri, 21 Jan 2005 05:27:47 GMT
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http://issues.apache.org/bugzilla/show_bug.cgi?id=33190

           Summary: Facility for passing an Iterator object into the 'View'
                    part of an MVC framework
           Product: Commons
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Collections
        AssignedTo: commons-dev@jakarta.apache.org
        ReportedBy: phil-apache@whirlycott.com


Note that this enhancement is not Struts/OJB/etc specific: I'm just using this
as an example that I believe will be easy for people to relate to.  Generally
stated, I'm proposing a special Iterator implementation that will automatically
close resources at the end of the iteration.

If you're using an MVC framework like Struts or Spring, there's a frequent need
to pass Iterator objects into the request scope so that a JSP in the View can
loop over the Iterator and, for example, print out some values.

If you are reading a large number of records from a DB, you could create a copy
of the Collection in your Action class and pass an Iterator through by dropping
it into the request.  A better approach that requires less memory is one which
would allow you to pass an Iterator object that performs lazy initialization,
since this is more efficient in terms of memory use.  

However, because the View and the Controller are seperate layers, you would need
to close your database connection before forwarding the request to the JSP. 
Since, in Struts, your Action class's execute() method has already terminated at
this time, you're left with ugly hacks like using scriptlet code to call close()
on certain objects.  

The approach that I'm proposing here is one which I picked up off of the OJB
user list a while ago.  I've implemented a special Iterator() that calls close()
on an resource object when there are no more elements in the iteration.

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