Slides part of the online Codename One introductory course created in 2017.

1. How do I?

2. Use Networking & WebServices

3. Mobile Is Different
✦Network is unreliable
✦iOS Prohibits HTTP and insecure communication
✦Sockets are possible but might be unreliable
✦Server sockets are difficult and less portable
✦WebSockets are rising

4. ConnectionRequest URL Socket WebSocket
Builtin Builtin
2 implementations
builtin & cn1lib
cn1lib
Modeled on JavaScript
async networking model
Modeled on java.net.URL
Builtin - async API
cn1lib - low level stream API
Low level callback API
Threaded Seamlessly Manual threading
Builtin - seamless threading
cn1lib - manual threading
Threaded Seamlessly
Synchronous &
asynchronous API’s
Synchronous API
Builtin - asynchronous
cn1lib - synchronous
Asynchronous
Highly Portable Portable
Builtin - iOS/Android
cn1lib - portable but low
level
Portable
Secured thru HTTPS Secured thru HTTPS Insecure Secured thru SSL
4 Network Options

5. Connection Request
ConnectionRequest c = new ConnectionRequest(url, false);
addToQueue(c);
import static com.codename1.ui.CN.*;

6. 3 Options
c.addResponseListener(e -> {
byte[] response = e.getConnectionRequest().getResponseData();
// do something with the response data
});
ConnectionRequest c = new ConnectionRequest(url, false) {
@Override
protected void readResponse(InputStream input) throws IOException {
// read input stream
}
};
addToQueueAndWait(c);
byte[] response = c.getResponseData();
// do something with the response data

7. Builtin Sockets
Socket.connect(server, port, new SocketConnection() {
@Override
public void connectionError(int errorCode, String message) {
Log.p("Error connecting " + errorCode + ": " + message);
}
@Override
public void connectionEstablished(InputStream is, OutputStream os) {
while(connected) {
// read and write to input/output stream
}
}
});

8. WebSockets
WebSocket sock = new WebSocket(websocketUrl) {
@Override
protected void onOpen() {
// we can start using the websocker
}
@Override
protected void onMessage(String string) {
// received string message from server
}
@Override
protected void onMessage(byte[] bytes) {
}
@Override
protected void onError(Exception excptn) {
Log.e(excptn);
}
};
sock.connect()

9. URL
✦You can port code that uses java.net.URL to use
com.codename1.io.URL
✦You will need to handle threading on your own
✦There is no builtin support for events on the event
dispatch thread
✦You might inadvertently rely on low level platform
specific behaviors since URL is low level

10. WebServices
✦WebService wizard can generate server client stubs
for remote method call over HTTP
✦ConnectionRequest can be used to invoke typical
restful webservices
✦Several cn1lib’s and builtin API’s exist to simplify
webservice calls e.g. com.codename1.io.rest.Rest
✦JSONParser & XMLParser support parsing common
formats the Result class supports XPath expressions

11. Connection Request WebService
ConnectionRequest req = new ConnectionRequest(nextURL, false) {
@Override
protected void readResponse(InputStream input) throws IOException {
JSONParser parser = new JSONParser();
Map response = parser.parseJSON(new InputStreamReader(input, "UTF-8"));
items = (List)response.get("items");
nextURL = (String)response.get("nextPage");
}
@Override
protected void handleException(Exception err) {
Log.e(err);
}
};
addToQueueAndWait(req);

12. Rest WebService
Response<Map> resultData = Rest.get(nextURL).
acceptJson().getAsJsonMap();
if(resultData.getResponseCode() != 200) {
Log.p("Error code from the server: " +
resultData.getResponseCode() + "n");
return;
}
items = (List)resultData.getResponseData().get("items");
nextURL = (String)resultData.getResponseData().get("nextPage");

13. Thank You!