Checking a bytes array is a primitive JSON type

[ppatierno]

I am getting an array of bytes which could represent a plain Java String (so not JSON one, no quotes around).
What I am able to do with GSON library is to check that it is a plain String because GSON has the concept of JsonPrimitive so I can do something like this:

JsonElement json = JsonParser.parseString(new String(bytes, StandardCharsets.UTF_8));
if (json.isJsonPrimitive()) {
   ....
} else {
   ....
}

I am not able to do something similar with the ObjectMapper. Any try with readTree or readValue fails with an exception which is the same as the JSON was invalid. I am not able to distinguish the two scenarios.
Is there a good way to do that?

[sixcorners]

Can't you use the exception to tell you if it is or is not json? Is there something else you are trying to tell about the string? I don't think there is a method to tell you if someone tried to give you json but it was invalid vs someone didn't try at all to give you json.
Do you have an example string?

[ppatierno]

Assume I get this array of bytes [107, 101, 121, 45, 48], it represents the string key-0 (note, there are no double quotes or single quotes so it's not a JSON string but just a String).
GSON is able to parse anyway that string and telling me it's a JSON primitive String type but not a JSON String or a JSON node.
Jackson just fails with this exception:

com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'key': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false')
 at [Source: (byte[])"key-0"; line: 1, column: 5]

Which could be the same you have when someone is trying to pass me a JSON but it's malformed.
I know that's a tricky problem and I see your point, but GSON provides that way to tell you it's not a JSON itself but a primitive type used in JSON, which is smart enough for my use case.

[sixcorners]

What is an example of a string you would want it to say no to? Can't basically any bytes wind up in a string? {"a": .} This is a valid primitive type string isn't it?

[ppatierno]

Yes, in the end we decided to stick with handling just JSON because everything could be just a string ... even a malformed JSON. What GSON provides is useful but could be misleading for the use case.
Anyway thanks for the discussion.

[cowtowncoder]

Right, that content can be made one with a simple transformation here (surround with double quotes). But that is not anything specified in JSON spec, nor widely used convention.

I suspect GSON adopted this approached from 'org.json' parser which for some reason supported handling of certain non-JSON content. Which seemed quite surprising, given that author of JSON was dead set against supporting most other variants, in particular adoption of comments.

But that's neither here nor there I guess. :)