Java Object Serialization

Ergonomic java.io.Serializable parsing for JavaScript and TypeScript projects.

Example

import { ObjectInputStream } from "java-object-serialization";

class List {
    value: number = 0;
    next: List | null = null;
}

ObjectInputStream.RegisterObjectClass(List, "List", "7622494193198739048");

const data = "rO0ABXNyAARMaXN0aciKFUAWrmgCAAJJAAV2YWx1ZUwABG5leHR0AAZMTGlzdDt4cAAAABFzcQB+AAAAAAATcHEAfgAD";
const serialized = Buffer.from(data, "base64");

const stream = new ObjectInputStream(serialized);
const list1 = stream.readObject();
const list2 = stream.readObject();

The above code deserializes the example given in the Java Object Serialization specification:

class List implements java.io.Serializable {
    int value;
    List next;
    
    public static void main(String[] args) {
        List list1 = new List();
        List list2 = new List();
        list1.value = 17;
        list1.next = list2;
        list2.value = 19;
        list2.next = null;

        ByteArrayOutputStream o = new ByteArrayOutputStream();
        ObjectOutputStream out = new ObjectOutputStream(o);
        out.writeObject(list1);
        out.writeObject(list2);
        out.flush();
        ...
    }
}

There is a JavaSerializable interface that can be implemented to customize the deserialization behaviour for classes:

interface JavaSerializable {
    readObject?(stream: ObjectInputStream): void
    readResolve?(): any
}

readObject needs to be implemented for classes that were serialized with a writeObject implementation. As with the Java interface the methods on the passed in ObjectInputStream can be used to read data related to the class, including the defaultReadObject method to read and populate the standard serialized fields.

readResolve can be implemented to return an alternative value when deserializing, this can be useful to e.g. return a JavaScript array for java.util.ArrayList:

class ArrayList implements JavaSerializable {
    size: number = 0;
    elements: any[] = [];
    
    readObject(stream: ObjectInputStream): void {
        // Read in size, and any hidden stuff
        stream.defaultReadObject();
        
        // Read in capacity
        stream.readInt(); // ignored
        
        for (let i = 0; i < this.size; ++i) {
            this.elements.push(stream.readObject());
        }
    }
    
    readResolve(): any {
        return this.elements;
    }
}

JavaObjectStream.RegisterObjectClass(ArrayList, "java.util.ArrayList", "8683452581122892189");

Status

The full Java Object Serialization specification isn't covered, and the API surface isn't stable, but it is usable for parsing real data.

License

MIT