In this test, we are registering a tree type adapter for Id but it never gets invoked. Instead, the reflective type adapter gets invoked causing an exception.
This drops support for type hierarchy instance creators. I don't expect this to be a problem. We'll also detect fewer errors where multiple type adapters can serialize the same type. With APIs like getNextTypeAdapter, I think this might actually be an improvement!
revised GsonBuilder.registerTypeAdapter/registerTypeHierarchyAdapter to take streaming type adapters as well. Removed the typeAdapter() and typeHierarchyAdapter() methods from the public API.
- The cache interface has only one implementation. Drop the interface; we can add it back later if necessary.
- The DefaultTypeAdapters class contains one member class. Just make that a top-level class.
The motivation for this change is to give tree-style adapters precedence order in registration. This fixes the test I committed earlier today, where registration order was not honored.
This renamed ParameterizedTypeHandlerMap to the shorter 'TypeMap'. For type adapters, this is now only used for type hierarchy. We still need non-hierarchy support in TypeMap for instance creators; I'll be looking for workarounds to see if further simplification is possible here.
The most notable impact of this change is that it adds several new public APIs:
- The TypeAdapter abstract class
- The TypeAdapter.Factory interface
- Four new methods on GsonBuilder to register streaming TypeAdapters (via Factory, via Class, via TypeToken, and as a type hierarchy)
- Three new methods on Gson to lookup streaming TypeAdapters (by type, by class, and to get the next type adapter)
Still outstanding:
- Write beautiful prose to document the new APIs above
- Change GsonBuilder's precedence so that both old and new-style type adapters are registered in one lot
Replaced DEFAULT_SERIALIZERS, DEFAULT_DESERIALIZERS and DEFAULT_INSTANCE_CREATORS with a single EMPTY_MAP.
Removed obsoleted TODO from Gson.
made ParameterizedTypeHandlerMap.makeUnmodifiable a builder method that returns this instance.
Add setSerializeNulls() to JsonWriter, so nulls can be skipped from serialization. This does not yet impact JsonElementWriter.
One change in behavior: if the only value is skipped, we now emit "null" rather than "".
GSON 1.x applies different rules for versioning for classes vs fields. So, if you deserialize a
JSON into a field that is supposed to be skipped, the field is set to null (or default value).
However, if you deserialize it to a top-level class, a default instance is returned.
GSON 2.x returns null for the top-level class.