@DateTimeFormat(iso = ISO.DATE_TIME) should use optimized formatter for LocalDateTime [SPR-14958]

[spring-projects-issues]

Oliver Drotbohm opened SPR-14958 and commented

It looks like the usage of DateTimeFormatter.ISO_DATE_TIME to format LocalDateTime instances is significantly slower than a usage of DateTimeFormatter.ISO_LOCAL_DATE_TIME (see this benchmark for details).

It would be cool if we could switch to that DateTimeFormatter in case a LocalDateTime instance is to be converted.

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Affects: 4.3.4, 5.0 M3

Issue Links:

• #19239 Align ISO timezone parsing in DateFormatter with Joda-Time / JSR-310
• #19493 Improve performance for conversions using a method parameter based type descriptor with annotations

[spring-projects-issues]

Juergen Hoeller commented

We've got specific checks for printing LocalDate / LocalTime / LocalDateTime now, automatically switching to ISO_LOCAL_DATE / ISO_LOCAL_TIME / {{ISO_LOCAL_DATE_TIME}... but just for printing, not for parsing, since the non-local variants turn out to leniently strip zone information in an input string whereas the local variants strictly reject those. Since there is only a performance benefit in printing anyway according to my tests, this compromise should be alright.