John Hewson created PDFBOX-2566:
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Summary: Remove logging from operator classes
Key: PDFBOX-2566
URL: https://issues.apache.org/jira/browse/PDFBOX-2566
Project: PDFBox
Issue Type: Improvement
Components: PDModel
Affects Versions: 2.0.0
Reporter: John Hewson
Priority: Minor
Fix For: 2.0.0
I've been trying to get better control over the logging that occurs in the
operator classes, but it's not easy to do so. Ideally all logging could pass
through PDFStreamEngine so that subclasses can more easily filter what they
want. By using exceptions instead of logging for error cases, we allow more
fine-grained management of exceptions. For example, in my own code I wish for a
missing XObject to be a terminal failure, but it currently just results in a
log message, and I have to implement a custom DrawObject operator and copy &
paste over most of the code in order to catch this exception rather than
logging it.
I'm therefore going to move what little logging there is in the Operator
classes over to PDFStreamEngine, and to throw custom Exceptions rather than
writing silently to the log. The default implementation of processOperator in
PDFStreamEngine will then catch these custom exceptions and simply write them
to the log - keeping the current PDFBox behaviour. Only now consumers of
PDFStreamEngine can override processOperator and do their own exception
handling, e.g. I can choose to propagate the missing XObject exception instead
of logging it.
This might be useful for Preflight too, as it often wants to throw errors where
we would otherwise skip the offending object and just keep processing.
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