Re: [FileUpload] "final" DiskFileItem breaks code on upgrade to v2

Joel,

An alternative fix would be for you to use  Tomcat Migration Tool for 
Jakarta EE on commons-fileupload-1.x which will give you the 
commons-fileupload-1.x API but using the Jakarta EE namespace.

Or even more simply, leave the web application exactly as-is and deploy 
it to webapps-javaee and Tomcat will automatically migrate it from Java 
EE to Jakarta EE and then deploy it.

Mark


On 06/06/2025 14:06, Joel Griffith wrote:
> I can't say I know why there's a need for a subclass, unfortunately.  The
> people who wrote this code are long gone, I just have to maintain it.
> 
> Joel
> 
> On Thu, Jun 5, 2025 at 6:25 PM Gary Gregory <[email protected]> wrote:
> 
>> Hello Joel,
>>
>> 2.x is not a drop in replacement for 1.x. Why is there a need for a
>> subclass? Perhaps there is a feature we can add to 2.x before we finalize
>> the API.
>>
>> Gary
>>
>> On Thu, Jun 5, 2025, 14:01 Joel Griffith <[email protected]> wrote:
>>
>>> I manage a Tomcat/JSP webapp.  We are updating our source code to conform
>>> to the recent `javax` -> `jakarta` namespace change in the Servlet
>> package.
>>>
>>> The app uses the Apache Commons FileUpload package, which must be
>> upgraded
>>> from v1 to v2 as part of this change.
>>>
>>> FileUpload v1 contains a `DiskFileItem` class:
>>> ```
>>> org.apache.commons.fileupload.disk.DiskFileItem
>>> ```
>>>
>>> FileUpload v2 contains the corresponding class
>>> ```
>>> org.apache.commons.fileupload2.core.DiskFileItem
>>> ```
>>>
>>> Our webapp code, written for v1, extends `DiskFileItem`:
>>> ```
>>> public class MonitoredDiskFileItem extends DiskFileItem
>>> {
>>>      private MonitoredOutputStream mos = null;
>>>      private OutputStreamListener listener;
>>>
>>>      public MonitoredDiskFileItem(String fieldName, String contentType,
>>> boolean isFormField, String fileName, int sizeThreshold, File repository,
>>> OutputStreamListener listener)
>>>      {
>>>          super(fieldName, contentType, isFormField, fileName,
>> sizeThreshold,
>>> repository);
>>>          this.listener = listener;
>>>      }
>>>
>>>      public OutputStream getOutputStream() throws IOException
>>>      {
>>>          if (mos == null)
>>>          {
>>>              mos = new MonitoredOutputStream(super.getOutputStream(),
>>> listener);
>>>          }
>>>          return mos;
>>>      }
>>> }
>>> ```
>>>
>>> This breaks with the update to v2 with `error: cannot inherit from final
>>> DiskFileItem` because the `DiskFileItem` class was changed to `final`
>>> across versions.
>>>
>>> The migration guide at
>>> https://commons.apache.org/proper/commons-fileupload/migration.html
>>> doesn't
>>> give guidance at this level of detail.
>>>
>>> Is there anything I can do to salvage this code?  I know that I could
>>> compile my own version of the source code without the `final` keyword in
>>> `DiskFileItem.class`, but I have to assume there's a reason for it and
>> that
>>> it would break other aspects of the code.  I hope very much that there's
>> a
>>> simpler solution.  I'm a system administrator, not a programmer, so I
>>> cannot rewrite the package from scratch.
>>>
>>> Thanks,
>>> Joel
>>>
>>
>