Networking and HTTP

Another honest page: the framework does not ship a high-level HTTP client (no ergonomic Http.get() exposed to the app). You use java.net or a lib (OkHttp is already on the classpath, used internally by the maps).

The mandatory rule

Make the request off the paint thread and return with Component.onUI(...) to touch the UI (see Background work).

Download bytes — `Utils.getRemoteFile(url)`

Shortcut to download a URL’s content:

new Thread(() -> {
   byte[] dados = Utils.getRemoteFile("https://api.exemplo.com/dados");  // null on error OR on WebGL
   if (dados == null) { Component.onUI(() -> Hint.show("Falha na rede", 2000)); return; }
   String corpo = new String(dados);
   Component.onUI(() -> mostrar(corpo));
}).start();

⚠️ getRemoteFile returns null on HTTP error, exception and on WebGL/TeaVM — always check.

JSON with Jackson (not Gson)

The project standard is Jackson (com.fasterxml.jackson.databind.ObjectMapper):

ObjectMapper mapper = new ObjectMapper();
new Thread(() -> {
   try {
      byte[] json = Utils.getRemoteFile("https://api.exemplo.com/clientes");
      if (json == null) return;
      List<Cliente> clientes = mapper.readValue(json, new TypeReference<List<Cliente>>(){});
      Component.onUI(() -> lista.setItems(clientes));
   } catch (Exception e) { Debug.log("parse: " + e); }
}).start();

GET/POST with `java.net`

When you need control (headers, POST), use HttpURLConnection/OkHttp directly — always on a background thread, result back with onUI(...).

⚠️ WebGL/TeaVM limitations

On the Web target, HTTP calls have restrictions (CORS, no direct sockets) and getRemoteFile returns null. Handle that case or disable the feature on Web (see platforms).

Best practices

Never do networking on the paint thread — the UI freezes.
Jackson, not Gson (consistency with the rest of the project).
Check null/exception on every response; show the error to the user via Hint/Alert.

Common mistakes

Looking for Http.get()/a ready-made client — it doesn’t exist; use java.net/OkHttp.
Ignoring that getRemoteFile is null on WebGL.
Parsing/touching the UI directly on the network thread (without onUI).