JSON

Getting started

Flavour provides the ability to serialize and deserialize Java objects to and from JSON. The Java type system does not map to JSON clearly, so additional conventions and annotations are required. Jackson is a de-facto standard for Java-to-JSON serialization, hence Flavour supports a reasonable subset of Jackson annotations. This helps to achieve good adoption by developers who already use Java on the server and are familiar with Jackson. But most of all, the goal of implementing a subset of Jackson was to allow developers to reuse annotated classes both on the client and server side.

The main use-case for JSON serialization is communication with the server. In this case Flavour has a built-in solution, so you don’t have to deal with the JSON API directly. But there are some cases when you want to call the JSON API. The following example shows how to use it:

    MyClass a = new MyClass();
    a.foo = "hello";
    a.bar = 23;
    String json = JSON.serialize(a).stringify();
    System.out.println(json);

    MyClass b = JSON.deserialize(Node.parse(json), MyClass.class);
    System.out.println(b.foo + "," + b.bar);

where MyClass is defined like this:

public class MyClass {
    public String foo;
    public int bar;
}

this code must be self-descriptive. The main entry points to the JSON API are two methods from the JSON class: serialize and deserialize. Both operate on JSON nodes represented by Node class, so some additional code is required to convert to and from string.

Supported subset of Jackson

To learn Jackson annotations, you can read its official documentation. Here is the list of supported annotations:

Note that TeaVM optimizer often removes classes which are unreachable from anywhere. For example, it removes a class if it is never instantiated from reachable methods. In case of inheritance, when a subclass can only be instantiated by deserializer, TeaVM may remove the class. To prevent TeaVM from removing classes, you should always use @JsonSubTypes when you want polymorphic deserialization.


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