Automatically serialize/deserialize Java 8 datatype

[Praveen2112]

This patch adds support for automatically serializing and deserialzing for new "datatypes" introduced in Java 8 for jersey-media-json-jackson module.

Fixes #3637.

[jansupol]

This PR does not look right:

• the newly used module jackson-datatype-jdk8 is deprecated.
• the class JsonMapperConfigurator.java which is being modified is repackaged JsonMapperConfigurator.java from Jackson - and Jackson itself does not do this in 2.9 nor in 2.10 branch. Have you considered to create the PR to Jackson itself?
• this PR cries for a test - adding new functionality which allows for using Optional
• the PR breaks jersey-tests-osgi-functional tests

[Praveen2112]

hi, thanks for your comment

the newly used module jackson-datatype-jdk8 is deprecated.

I have checked it from Jackson modules jdk8 it looks like they share a same group and artifactID.

I'll add test for the same and debugging on why jersey-tests-osgi-functional test fails

[jansupol]

jersey-tests-osgi-functional likely failed because you need to modify the JsonJacksonTest to contain mavenBundle().groupId("com.fasterxml.jackson.core").artifactId(jackson-datatype-jdk8").versionAsInProject().

However, I am not convinced we should modify the repackaged JsonMapperConfigurator.

[Praveen2112]

Actually we can modify the JsonMapperConfigurator in the jackson library but the problem is Jackson-Jaxrs library can also run in Java version before 1.8 so adding them there might break it. And I think from 3.0 version Jackson runs only Java version above 8 so Jdk-8 module would be a part of it. (But it is not released ). So once we move to the 3.0 of Jackson we wouldn't require this dependency

[jansupol]

The preferred way to do this should be to extend JacksonJsonProvider and pass the ObjectMapper with predefined Jdk8Module to be registered. But I am not sure this should be a class in Jersey, it sounds more like a user-specific class, especially when Jackson 3 would not need this.

What might be better is an extended JacksonJsonProvider that would get com.fasterxml.jackson.databind.Module from the @Context Configuration and pass it to JacksonJsonProvider, so that you could use the configuration mechanism to specify the needed modules.

[Praveen2112]

Okay. Will close it and work on the latter approach. Thank you for your insights.

[jansupol]

Actually, now I look at their repo, they have it as a service. So it should be automatically loaded when on classpath by Jackson somehow.

[jansupol]

I cannot find a code that uses ServiceLoader and in the tests, the Module is registered manually. If that is not handled by Jackson itself, maybe it can be done in Jersey JacksonFeature.

[Praveen2112]

But aren't those features are a part of Jackson 3.0 ?

[jansupol]

Maybe. But 3.0 may have a few months before release and the services are available for Jackson 2.x.