Encoding collection to json array in jsr 356

Question

I am learning websockets and my webapp is using jsr 356 library. I followed the tutorials and I can encode/decode POJOs, however I can't find examples on how to serialize either arrays or collections to JSON.

This is what I am doing to encode my data:

@Override
public String encode(ScanPlus scan) throws EncodeException {

    JsonObject jsonObject = createJsonObject(scan);
    return jsonObject.toString();

}

private JsonObject createJsonObject(ScanPlus scan) {
    JsonObject jsonObject = Json.createObjectBuilder()
            .add("scan", scan.getCode())
            .add("creationdate", String.valueOf(scan.getCreationDate()))
            .add("username", scan.getUserName())
            .build();
    return jsonObject;
}

public String encode(ArrayList<ScanPlus> scans) throws EncodeException {

    JsonArrayBuilder jsonArray = Json.createArrayBuilder();

    for (ScanPlus scan : scans) {
        JsonObject jsonObject = createJsonObject(scan);
        jsonArray.add(jsonObject);
    }

    return jsonArray.toString();

}

This is how I send the data to the encoder:

@OnOpen
public void onOpen(Session session, @PathParam("username") String username)    {
    ...
    session.getBasicRemote().sendObject(scans);
}

And this is the exception I am getting:

javax.websocket.EncodeException: No encoder specified for object of class [class java.util.ArrayList]

Could anyone give me a hint on how to do it?

thanks

Answer 1

You need to create Encoder<ArrayList<ScanPlus>>; Encoder<ScanPlus> is not enough..