On 12/02/2022 01:21, Xeno Amess wrote:
> I think the class loader will fail to load `ObjectMapper` breaking things.I don't think so... Maybe it is worth to have a try
I gave this a try with a snapshot build, adding a dummy `readValue(JsonParser, Path, Class<T> valueType)` method to ObjectMapper. As Jonas and Xeno thought, older Android devices are able to load and use the ObjectMapper class as long as they don't call this method.
I don't know whether the dummy method is removed by ProGuard or whether the reference to Path is resolved lazily by the class loader, but either way it seems to work.
As another experiment, I modified the `readValue(JsonParser, Class<T> valueType)` method to call through to the dummy method, using `Paths.get("/")` to create the Path parameter. My old device was still able to load and instantiate the ObjectMapper class, but calling the modified readValue() method caused a NoClassDefFoundError for java.nio.file.Paths. This suggests that references to unknown classes can safely exist even if they're not removed by ProGuard, and the class loader resolves references lazily.
So in short, it looks like adding a method that uses Path is fine, as long as that class isn't used on any call paths that need to remain backward compatible.
Cheers, Michael
Tatu Saloranta <[email protected] <mailto:[email protected]>> 于2022年 2月12日周六 06:52写道：On Fri, Feb 11, 2022 at 10:45 AM [email protected] <mailto:[email protected]> <[email protected] <mailto:[email protected]>> wrote: > > A missing class for a method parameter shouldn't affect you, you could simply not use that method. If it was a field it'd be a different story. > > - Jonas I don't think that is correct in this case? If a method signature for `ObjectMapper.readValue(Path src, Class<?> target)` is encountered, I think the class loader will fail to load `ObjectMapper` breaking things. Or is this not the case? I do know that if `Path` was known but referred to something else itself that wasn't, that'd be fine. But in this particular case I would expect actual trouble even if that specific `readValue()` method was not called. -+ Tatu +- > > Michael Rogers schrieb am Freitag, 11. Februar 2022 um 13:48:44 UTC+1: >> >> On 01/02/2022 18:28, Tatu Saloranta wrote: >> > On Mon, Jan 24, 2022 at 8:13 PM Xeno Amess <[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>> wrote: >> > >> > Hi. >> > Is there any reason not support Path in JsonFactory and ObjectMapper? >> > If not, then I would provide a pr when I have time. >> > >> > >> > The main reason is that `Path` was added in JDK 7 and for the longest >> > time Jackson only required JDK 6. >> > >> > With 2.13 jackson-databind requires JDK 8, so adding support in >> > `ObjectMapper` (and `ObjectReader`) would be fine. >> > >> > `jackson-core` (JsonFactory / TokenStreamFactory) however still only >> > requires JDK 6 for 2.13, and while >> > we may consider upgrading the baseline within 2.x no decision has been >> > made (or proposal) for 2.14. >> > So addition in JsonFactory would not yet be possible. >> > >> > So, a PR against `2.14` (this is API add so can not go in as part of >> > 2.13.x patches) for `jackson-databind` would be welcome. >> > >> > Anyone else have comments, suggestions, wrt this question? >> >> Older Android devices only have support for the Java 6 standard library. >> Some parts of the Java 8 standard library are supported via library >> desugaring, but unfortunately Path doesn't seem to be among them: >> >> https://developer.android.com/studio/write/java8-support-table <https://developer.android.com/studio/write/java8-support-table> >> >> So adding Path to jackson-databind would make it incompatible with about >> 3.4% of Android devices (according to apilevels.com <http://apilevels.com>). As an app >> developer currently using 2.13, this would stop me from upgrading to >> 2.14 for another couple of years, while those old devices gradually die out. >> >> Cheers, >> Michael >> >> > -+ Tatu +- >> > >> > -- >> > You received this message because you are subscribed to the Google >> > Groups "jackson-user" group. >> > To unsubscribe from this group and stop receiving emails from it, >> > send an email to [email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>. >> > To view this discussion on the web visit >> > https://groups.google.com/d/msgid/jackson-user/96b2fcd7-3f1c-48fa-aadd-15ff6f3b85abn%40googlegroups.com <https://groups.google.com/d/msgid/jackson-user/96b2fcd7-3f1c-48fa-aadd-15ff6f3b85abn%40googlegroups.com> >> > <https://groups.google.com/d/msgid/jackson-user/96b2fcd7-3f1c-48fa-aadd-15ff6f3b85abn%40googlegroups.com?utm_medium=email&utm_source=footer <https://groups.google.com/d/msgid/jackson-user/96b2fcd7-3f1c-48fa-aadd-15ff6f3b85abn%40googlegroups.com?utm_medium=email&utm_source=footer>>. >> > >> > -- >> > You received this message because you are subscribed to the Google >> > Groups "jackson-user" group. >> > To unsubscribe from this group and stop receiving emails from it, send >> > an email to [email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>. >> > To view this discussion on the web visit >> > https://groups.google.com/d/msgid/jackson-user/CAGrxA24hYAiFW1xymfxBcNRqwYTkEakCm8ikO7bwbeuLdXcwsw%40mail.gmail.com <https://groups.google.com/d/msgid/jackson-user/CAGrxA24hYAiFW1xymfxBcNRqwYTkEakCm8ikO7bwbeuLdXcwsw%40mail.gmail.com> >> > <https://groups.google.com/d/msgid/jackson-user/CAGrxA24hYAiFW1xymfxBcNRqwYTkEakCm8ikO7bwbeuLdXcwsw%40mail.gmail.com?utm_medium=email&utm_source=footer <https://groups.google.com/d/msgid/jackson-user/CAGrxA24hYAiFW1xymfxBcNRqwYTkEakCm8ikO7bwbeuLdXcwsw%40mail.gmail.com?utm_medium=email&utm_source=footer>>. > > -- > You received this message because you are subscribed to the Google Groups "jackson-user" group. > To unsubscribe from this group and stop receiving emails from it, send an email to [email protected] <mailto:jackson-user%[email protected]>. > To view this discussion on the web visit https://groups.google.com/d/msgid/jackson-user/2109c03c-15b2-40b7-8b35-afa80b2f6505n%40googlegroups.com <https://groups.google.com/d/msgid/jackson-user/2109c03c-15b2-40b7-8b35-afa80b2f6505n%40googlegroups.com>.-- You received this message because you are subscribed to the GoogleGroups "jackson-user" group. 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