[MIME4J-158] Reduce usage of commons-logging in favor of a "Monitor" service.

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.6
• Fix Version/s: 0.7
• Assignee: Stefano Bagnara
• Reporter: Stefano Bagnara
• Created: 02/Jan/10 21:41
• Updated: 06/Feb/10 12:14
• Resolved: 06/Feb/10 12:14

Description

We should remove commons-logging usage from mime4j. At least starting from low level utilities and libraries.

The solution could be in some code reorganization and the introduction of a "monitorservice" passed to the various methods around the code.
The "monitorservice" could also be used to "alter" the strictness/lenientness of the parsing/decoding operations.

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CharsetDecoder uses a combination of fluent api (CharsetDecoder.onMalformedInput) with a CodingErrorAction parameter.
CodingErrorAction is a simple enumeration (IGNORE, REPLACE, REPORT) and allow some methods to return CoderResult that is an object describing the various conditions (error/malformed/underflow/overflow/unmappable)

Another approach, instead, is the ErrorHandler from SAX: ErrorHandler expose the error/fatalError/warning methods, and all of them has a SAXParseException parameter, containing a message and a "locator".

We need both:

• a way to control how to deal with malformed/unexpected data (IGNORE/REPLACE/REPORT)
• a way to log malformations and their positions in the stream/field (like SAX ErrorHandler).

Maybe introducing a mixed service handling both use-cases is the best approach: basically a service that tells wether to "ignore", or "report", and if "report" then in the reporting methods it could alter the behaviour.
E.g: decoding QuotedPrintable we could ignore bad =XX sequences or leave them as is in output. For both cases we should be able to intercept and log the fact, or stop the processing with an IoException.