Improve support for deserializing from TokenBuffer (f.ex for content buffered for non-blocking parsing)

[sdeleuze]

Is your feature request related to a problem? Please describe.

With Jackson 3, in order to support customer deserializers (specified with @JsonDeserialize(using = Deserializer.class)) with non-blocking parsing, Spring has to do mapper.readerFor(javaType).readValue(tokenBuffer.asParser(mapper._deserializationContext())) in its AbstractJacksonDecoder.

We introduced this using Jackson 2 via spring-projects/spring-framework#20526, but with Jackson 3 that's not ideal given the fact that ObjectMapper#_deserializationContext() is advertised as "only public to allow for testing".

With just mapper.readerFor(javaType).readValue(tokenBuffer.asParser()) we get an UnsupportedOperationException with "Operation not supported by ObjectReadContext of type tools.jackson.core.ObjectReadContext$Base".

Describe the solution you'd like

We would like that Jackson 3 offers a way to do non-blocking parsing of instance of classes with customer deserializers without having to invoke a test-related method.

Usage example

No response

Additional context

No response

[cowtowncoder]

Hmmh. This will require some thinking. Perhaps specialized readValue() method that takes in TokenBuffer as source and can construct parser with DeserializationContext it manages.

[cowtowncoder]

@sdeleuze I hope this works: now you can use

• ObjectMapper.readValue(tokenBuffer, type)
• ObjectReader.readValue(tokenBuffer)

which will properly construct and pass DeserializationContext to use.

As an added bonus added

• ObjecMapper.writeValueIntoBuffer(Object)
• ObjecWriter.writeValueIntoBuffer(Object)

which seem like useful things even if not needed for this use case.