Ability to configure indentation

[hohwille]

Indent is currently hardcoded:
https://github.com/eclipse-ee4j/jsonp/blob/9892c0658f9d55b819d39039a364df37d1d60202/impl/src/main/java/org/glassfish/json/JsonPrettyGeneratorImpl.java#L31

I prefer two spaces as indendation. To change I would have to replace the entire implementation. It should be trivial to create a configuration property so the indent could be set via the config map supplied to the generator factory.
WDYT?

[keilw]

It sounds good, but any idea where to store that?
Unlike JSONB this API so far has no config mechanism.

[leadpony]

We already have a configuration property PRETTY_PRINTING defined in JsonGenerator interface. I believe this is where additional standard properties should be added.
Also I am implementing this proposed nice feature as a provider-specific configuration property in Joy, which is yet another implementation of JSON-P API.

[keilw]

That property value is a little weird saying "The value of the property could be be anything.". Meaning it's totally up to an implementation what kind of value they use to control PRETTY_PRINTING.
How does Joy use the existing entry?

[leadpony]

If a map given to Json#createGeneratorFactory(Map<Strng,?>) contains the key PRETTY_PRINTING, any implementation of JsonGenerator must do pretty printing, regardless of the value of the key. This feature is equally supported by the Reference Implementation, Apache Johnzon, and Joy.

I added two configuration properties INDENTATION_SIZE and TAB_INDENTATION to my own JsonGenerator which extends the standard interface to control the detail of the pretty printing.
Please see Beyond the Standard API.
I hope that these properties or something similar will be officially added to the JsonGenerator interface of JSON-P API anytime soon at some future date.

[keilw]

Funny because it's not written down anywhere not even in JavaDoc, maybe you could help with the spec by writing some of that down as mentioned here? ;-)