RFR: 8072645: java.util.logging should use java.time to get more precise time stamps

[Daniel Fuchs]

Hi,

Please find below a patch for:

8072645: java.util.logging should use java.time to get more
          precise time stamps


http://cr.openjdk.java.net/~dfuchs/webrev_8072645/webrev.00/

specdiff:
http://cr.openjdk.java.net/~dfuchs/webrev_8072645/specdiff-logging-time/java/util/logging/package-summary.html

Overview:
---------

The patch is made of the following pieces:

  - LogRecord uses java.time.Clock's systemClock to get an
    Instant in the best available resolution.

    The instant is split into a number of milliseconds (a long)
    and a nanosecond adjustment (an int).
    The number of milliseconds is the same than what would have
    been obtained by calling System.currentTimeMillis().

  - LogRecord acquires a new serializable int nanoAdjustement field,
    which can be used together with the number of milliseconds
    to reconstruct the instant.

  - SimpleFormatter is updated to pass a ZoneDateTime
    instance to String.format, instead of a Date.

    The effect of that is that the format string can now
    be configure to print the full instant precision, if
    needed.

  - XMLformatter will add a new <nanos> element after the
    <millis> element - if the value of the nanoAdjustment
    field is not 0.

    The <date> string will also contain the nano second
    adjustment as well as the zone offset as formatted by
    DateTimeFormatter.ISO_OFFSET_DATE_TIME

Compatibility considerations:
-----------------------------

- The serial for of log record is backward/forward compatible.
   I added a test to verify that.

- XMLFormatter has acquired a new configurable property
   '<FQCN>.printNanos' which allows to revert to the old
   XML format, should the new format cause issues in
   existing applications.

- The logger.dtd will need to be updated, to support the
   new optional <nanos> element. And for this matter,
   should we update the logger.dtd or rather define a
   logger-v2.dtd?
   See planned modification:
 
<http://cr.openjdk.java.net/~dfuchs/webrev_8072645/logger-dtd/logger.dtd.frames.html>

best regards,

-- daniel