回复：Towards a JSON API for the JDK

[wenshao]

As the author of a popular json library (fastjson/fastjson2), I think the current design is not good, not easy to use, and the performance is not good.
The JsonNull/JsonNumber/JsonString/JsonValue here should not be designed like this, which will cause trouble to users and affect performance.
For simple types of JSON, you can directly use Java type mapping, such as:
null -> null
string -> string
number -> integer/long/bigint/float/double, select the mapping type through configuration, or according to a rule we set.
Array and Object types should also support more flexible mapping:
object -> JsonObject or Map (HashMap/LinkedHashMap/ConcurrentHashMap...)
array -> JsonArray or List(ArrayList/LinkedList/...) or typed-array
Lazy parsing should not be used because it will degrade performance. If we need to support partial parsing, we can provide a skip api, and later we can provide a jsonpath api, or support passing in type/JsonSchema information and parsing according to the schema.
Also, if we want better performance, both Parser and Generator should provide both UTF16 and UTF8 implementations.
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发件人：forax <forax at univ-mlv.fr>
发送时间：2025年5月17日(周六) 02:43
收件人：Brian Goetz<brian.goetz at oracle.com>
抄　送：Paul Sandoz<paul.sandoz at oracle.com>; "core-libs-dev"<core-libs-dev at openjdk.org>
主　题：Re: Towards a JSON API for the JDK
From: "Brian Goetz" <brian.goetz at oracle.com>
To: "Remi Forax" <forax at univ-mlv.fr>
Cc: "Paul Sandoz" <paul.sandoz at oracle.com>, "core-libs-dev" <core-libs-dev at openjdk.org>
Sent: Friday, May 16, 2025 7:46:09 PM
Subject: Re: Towards a JSON API for the JDK
If you read the implementation, you'll see that significant laziness is indeed possible for JsonObject and JsonArray, even while doing eager validation. (Of course, one can shift the balance to achieve various other tradeoffs.)
Reading the implementation is on my TODO list :)
Rémi
On 5/16/2025 10:35 AM, forax at univ-mlv.fr <mailto:forax at univ-mlv.fr > wrote:
----- Original Message ----- From: "Brian Goetz" <brian.goetz at oracle.com> <mailto:brian.goetz at oracle.com > To: "Remi Forax" <forax at univ-mlv.fr> <mailto:forax at univ-mlv.fr >, "Paul Sandoz" <paul.sandoz at oracle.com> <mailto:paul.sandoz at oracle.com > Cc: "core-libs-dev" <core-libs-dev at openjdk.org> <mailto:core-libs-dev at openjdk.org > Sent: Friday, May 16, 2025 2:53:18 PM Subject: Re: Towards a JSON API for the JDK On 5/15/2025 5:27 PM, Remi Forax wrote: It's not clear to me why JsonArray (for example) has to be an interface instead of a record ? Oh, you know the answer to this. A record limits us to a single implementation with a rigid representation. Behind an interface, we can hide lazy parsing and inflation, wrapping other representations to reduce copies, etc. First, let me refine the question. There are only 4 kinds of JSON values that benefit from having different representations, object, array, string and number. For object and array, both takes an interface as parameter (Map or List) so JsonArray and JSonObject do not need to be themselves interfaces. So the only values where it may be worth to be modeled using an interface are JsonString and JsonNumber, because as you said, you can do "lazy" parsing. But delaying the parsing of the content has the side effect that even if Json.parse() did not throw an exception, it does not mean that the JSON text is valid, an exception may be thrown later. Now, for me, this library is more about being simple and safe than fast. If you agree with that, delaying the parsing is not a good idea, thus JSON values should be modeled using records and not interfaces. regards, Rémi 
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