doytsujin / jsonwheel

A 200 lines single-source-file hackable JSON deserializer for the JVM. Reinventing the JSON wheel.

JSON Wheel

Have you ever written scripts in Java 11+ and needed to operate on some JSON string? Have you ever needed to extract just that one deeply-nested value of an application/json response without modelling the whole hierarchy? Have you ever felt someone should indeed reinvent that wheel and provide the JVM universe with yet another JSON deserializer?

If the answer to any of those is "yes" then look no further, JSON Wheel's got you covered! It's a 200 lines single-source-file hackable JSON deserializer written in plain Java.

If the answer is "no" I still had fun writing it. :)

It is ...

• small
• deserialization-only
• hackable
• compatible to JDK 11+
• dependency-less
• not tooo slow

It is not ...

• typed (except for its own API's types)
• safe for malformed input
• safe for malicious input (at least I don't give that guarantee)

Usage

Either

a) copy the content of JsonWheel.java as-is into your existing class (remove imports if colliding with your pre-existing ones), or

b) copy the whole JsonWheel.java over into your app (adjust the package declaration if needed).

Then you can ...

1) Deserialize JSON objects

var json = """
    {
        "foo": 1,
        "bar": "baz",
        "qux": null
    }""";

var node = JsonWheel.read(json);
var a = node.get("foo").val(Integer.class); // 1
var b = node.get("bar").val(String.class);  // "baz"
var b = node.get("qux").val(String.class);  // null

2) Deserialize JSON arrays

var json = """
    [
        1,
        2,
        3
    ]""";

var node = JsonWheel.read(json);
var list = node.elements()
        .stream()
        .map(e -> e.val(Integer.class))
        .toList();  // 1 2 3

3) Deserialize "complex" JSON

var json = """
    {
        "foo": {
            "bar" : [
                1,
                2,
                3
            ],
            "baz": "qux"
        }
    }""";

var node = JsonWheel.read(json);
var bar = node.get("foo").get("bar").elements()
        .stream()
        .map(e -> e.val(Integer.class))
        .toList(); //   1 2 3
var baz = node.get("foo").get("baz").val(String.class); //  "qux"