Creation and Thread-Safety

[falkreon]

Right now, the start of any Jankson interaction is Jankson.builder().build(), often completely uncustomized.

Good:

• This allows deep customization of the json processor which is built
• Builder data is immutable, making deserialization more stable and helping us move towards thread-safety

Bad:

• Thread-safety is not documented, and nothing is threadsafe
• Beginner users forced through several steps to create an object they immediately throw away
• What is a Jankson?

There are two proposals really that could move us in the right direction.

Option 1: Incremental improvement

• Convenience static methods on Jankson to Just Get An Object using a default deserializer.
• Return threadsafe objects
• Reverse the internal builder logic so that it gets handed to the constructor, which queries the builder and sets internal fields, instead of the builder stuffing data into internal fields.

Option 2: Redesign

Instead of opening json with a Jankson, open a json with a JsonReader (think ZipInputStream). This better communicates the single-use / threaded nature of the object, and gives us a really nice middle ground for interacting with either the document API, semantic objects, or both.

Creating the JsonReader presents some design challenges, since the Reader needs access to a whole marshaller and all those other nice builder settings. So we could make them an optional constructor argument: new JsonReader(new FileReader(foo)) versus new JsonReader(new FileReader(foo), settings).

Specifically, settings could be a DeserializerSettings set up with only those related to unpacking json, not writing it, because...

you could write json with a JsonWriter. Same constructor flow, with an optional SerializerSettings.

Then we could provide bigger concepts like some kind of threadsafe dispatcher to spin off readers and writers with related settings.

Thoughts?