How do I make a class definition for an ArrayList<byte[]>

Question

I am trying to make my class implement VersionedPortable. It has a field

ArrayList<byte[]> someMessages = new ArrayList<>();

How do I specify this field in my ClassDefiniton? I assume it would be something like

new ClassDefinitionBuilder(FACTORY_ID, MESSAGE_BUNDLE_CLASS_ID, VERSION_ID)
              .addPortableArrayField("someMessages", ?? what goes here ??)

And how would I read and write them?

Answer 1

Arrays of arrays are not supported in the Portable format by default. However, you can use the following trick to wrap the nested array as a separate Portable type and write your field as a Portable array.

class Foo implements Portable {

    private ArrayList<byte[]> messages;

    @Override
    public int getFactoryId() {
        return 1;
    }

    @Override
    public int getClassId() {
        return 1;
    }

    @Override
    public void writePortable(PortableWriter writer) throws IOException {
        Portable[] wrappedMessages = messages.stream()
                .map(ByteArrayWrapper::new)
                .toArray(Portable[]::new);
        writer.writePortableArray("messages", wrappedMessages);
    }

    @Override
    public void readPortable(PortableReader reader) throws IOException {
        messages = Arrays.stream(reader.readPortableArray("messages"))
                .map(item -> ((ByteArrayWrapper) item).getArray())
                .collect(Collectors.toCollection(ArrayList::new));
    }
}

class ByteArrayWrapper implements Portable {

    private byte[] array;

    public ByteArrayWrapper() {
    }

    public ByteArrayWrapper(byte[] array) {
        this.array = array;
    }

    @Override
    public int getFactoryId() {
        return 1;
    }

    @Override
    public int getClassId() {
        return 2;
    }

    @Override
    public void writePortable(PortableWriter writer) throws IOException {
        writer.writeByteArray("array", array);
    }

    @Override
    public void readPortable(PortableReader reader) throws IOException {
        array = reader.readByteArray("array");
    }

    public byte[] getArray() {
        return array;
    }
}