8000685: (props) Properties.storeToXML/loadFromXML should only require UTF-8 and UTF-16 to be supported

[Chris Hegarty]

Changes Look fine. Nice test too.

-Chris

On 12 Oct 2012, at 11:19, Alan Bateman <Alan.Bateman at oracle.com> wrote:

> 
> A few days ago we added a JDK private provider interface [1] to which the Properties loadFromXML and storeToXML methods will delegate. The motive as I mentioned is to allow for a smaller environments where JAXP might not be present (so motivated by both modules and the compact profiles work).
> 
> The next step in this effort is dealing with the issue of arbitrary encodings. The storeToXML method allows the encoding to be specified, the loadFromXML method assumes that the implementation can decode the stream and read the encoding declaration. The specification doesn't make it clear how either method behaves with unrecognized encodings and this is something that we need to fix in order to allow for alternative implementations, in particular tiny parsers that might not support more than a few.
> 
> The webrev the proposed changes is here:
> 
> http://cr.openjdk.java.net/~alanb/8000685/webrev/
> 
> The proposal is that an implementation minimally supports UTF-8 and UTF-16, which I think is consistent with the W3C XML specification [2].
> 
> Based on a search of a large number of projects then it appears that these methods aren't used very much so I don't think this will have any significant impact. In addition the same set of encodings [ which is not exactly the same set as Charsets.availableCharsets().keySet() ] that works today will continue to work when the service provider that uses JAXP is installed.
> 
> In addition, to specifying the required encodings, I have also changed both methods to specify that UnsupportedEncodingException may be thrown. In the case of loadFromXML then this is the long standing behavior anyway. In the case of storeToXML then the long standing behavior is somewhat bizarre. If the method is invoked with an unsupported encoding then the underlying Xalan code prints a warning to System.out and changes the encoding under the covers to UTF-8. I've submitted a bug on this oddity; in the mean-time I've added a check in the platform provider to always fail for charsets that aren't recognized.
> 
> -Alan.
> 
> [1] http://hg.openjdk.java.net/jdk8/tl/jdk/rev/f65871e75fde
> [2] http://www.w3.org/TR/REC-xml/#charencoding