[BUG] Jackson dependency required when okhttp-gson is choosen

[efren1villamagua]

The generated code for java with okhttp-json has a problem.

For some in-house reason we can't use Jackson libraries.
Until version 7.2.0 the file JSON.java is generated with a Google dependency (com.google.gson.internal.bind.util.ISO8601Utils) but from 7.3.0 version a Jackson dependency is used (com.fasterxml.jackson.databind.util.StdDateFormat) what causes a compilation error.

Dependency used in my project is: org.openapitools:openapi-generator-gradle-plugin:7.5.0

Configuration is:

openApiGenerate {
    generatorName = "java"
    library = "okhttp-gson"
    inputSpec = "...".toString()
    outputDir = "...".toString()
    apiPackage = "..."
    invokerPackage = "..."
    modelPackage = "..."
    configOptions = [
            dateLibrary                             : "java8",
            disallowAdditionalPropertiesIfNotPresent: "false",
            enumUnknownDefaultCase                  : "true",
            useOneOfDiscriminatorLookup             : "true"
    ]
    globalProperties = [
            skipFormModel: "false",
            apiTests     : "false",
            modelTests   : "false"
    ]
    skipValidateSpec = true
    logToStderr = true
    generateAliasAsModel = false
    enablePostProcessFile = false
    cleanupOutput = true
}

[Philzen]

@winrid also seems affected by this.

I tend to share the expectation that generated gson clients should not contain any jackson dependency whatsoever, be it direct or transitive. Though GSON is in maintenance mode, the implementation in question has recently been committed to: https://github.com/Marcono1234/gson/blob/main/gson/src/main/java/com/google/gson/internal/bind/util/ISO8601Utils.java – so IMHO for GSON fanfolks this import should still be fine.

That change was introduced in 76560e3 via #17052. @ChaosMarc @martin-mfg i followed your discussion over there, so i'm trying to make the best of both worlds possible over via #18811 – i'm welcoming your comments.