Garret Wilson created WICKET-5691:
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Summary: Wicket FileUploadField.getFileUploads() should never
return null.
Key: WICKET-5691
URL: https://issues.apache.org/jira/browse/WICKET-5691
Project: Wicket
Issue Type: Improvement
Components: wicket
Reporter: Garret Wilson
Priority: Minor
{{FileUploadField}} at one point in its history (as far as I can tell) only
supported uploading a single file (as did HTML). Thus
{{FileUploadField.getFileUpload()}} returned a {{FileUpload}} or {{null}} if
there was no file uploaded. This is correct and works as expected.
After browsers added support for multiple file uploads, Wicket appropriately
added the {{FileUploadField.getFileUploads()}} method, which returns a
{{List<FileUpload>}}. This method's API documentation doesn't indicate whether
it returns {{null}}, a deficiency which itself should be corrected. In fact the
documentation seems to imply that {{null}} will never be returned. The
expectation from common practice is that a method returning a collection will
never return {{null}}, unless {{null}} indicates something semantically
distinct from an empty collection.
Unfortunately this method returns {{null}} when there are no files selected for
upload. This goes against developer expectation, and moreover serves no
semantic value, as an empty list would be just as appropriate (more
appropriate, actually) to indicate that no files were selected. It makes the
developer add extra, unnecessary code:
{code}
if(fileUpload.getFileUploads()==null || fileUpload.getFileUploads().isEmpty()) {
return; //no files to process
}
{code}
I recommend changing {{FileUploadField.getFileUploads()}} so that it never
returns {{null}} (but may return an empty list), and indicate such in the API
documentation. The currently implementation runs the risk of an unexpected
{{NullPointerException}} for the developer who followed common practice
expectations and was given no warning from the documentation.
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