[logback-dev] [JIRA] Updates for LOGBACK-1659: Unnecessary OffsetDateTime creation in CachingDateFormat

[QOS.CH (JIRA)]

logback / LOGBACK-1659 [Open]
Unnecessary OffsetDateTime creation in CachingDateFormat

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https://jira.qos.ch/browse/LOGBACK-1659

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 Issue created
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Bertrand Renuart created this issue on 13/Aug/22 4:27 PM
Summary:              Unnecessary OffsetDateTime creation in CachingDateFormat
Issue Type:           Improvement
Affects Versions:     1.3.0-beta0
Assignee:             Logback dev list
Components:           logback-core
Created:              13/Aug/22 4:27 PM
Priority:             Major
Reporter:             Bertrand Renuart
Description:
  CachingDateFormat creates a temporary OffsetDateTime from the given instant to apply the configured time zone (see [here|https://github.com/qos-ch/logback/blob/master/logback-core/src/main/java/ch/qos/logback/core/util/CachingDateFormatter.java#L68-L69]) before passing it to the DateTimeFormatter for rendering.
  
  This temporary OffsetDateTime can be avoided by setting the ZoneId directly on the DateTimeFormatter when it is initialized. This is apparently what was foreseen in the constructor with the following [lines|https://github.com/qos-ch/logback/blob/master/logback-core/src/main/java/ch/qos/logback/core/util/CachingDateFormatter.java#L58]:
  {code:java}
  public CachingDateFormatter(String pattern, ZoneId aZoneId) {
     dtf = DateTimeFormatter.ofPattern(pattern);
     ...
     dtf.withZone(this.zoneId);
     ...
  }{code}
  Unfortunately this won't work because "{{withZone()}}" returns a new formatter which is not assigned to the "{{dtf}}" instance variable...
  
   
  
  *To summarise:*
  
  (1) In the constructor do something like:
  {code:java}
  dtf = DateTimeFormatter.ofPattern(pattern).withZone(this.zoneId)
  {code}
  (2) In the "format()" method do something like:
  {code:java}
  Instant instant = Instant.ofEpochMilli(now);
  String result = dtf.format(instant);
  {code}
  --> no need for an intermediate OffsetDateTime anymore


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