1.
Leif Åstrand
Product Manager
Comparing GWT
Transport Mechanisms
lördag 24 januari 15

2.
Transport
lördag 24 januari 15

3.
RequestBuilder builder = new RequestBuilder(RequestBuilder.GET, url);
try {
builder.sendRequest(requestDataString, new RequestCallback() {
@Override
public void onResponseReceived(Request request, Response response) {
int statusCode = response.getStatusCode();
String text = response.getText();
}
@Override
public void onError(Request request, Throwable exception) {
// TODO Handle asynchronous problems
}
});
} catch (RequestException e) {
// TODO Handle synchronous problems
}
RequestBuilder
lördag 24 januari 15

4.
Good
• It just works
Bad
• Low level
RequestBuilder
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5.
Real world usage
8 %
lördag 24 januari 15

6.
What to send?
lördag 24 januari 15

7.
public class Contact {
private String name;
private int yearOfBirth;
private List<String> emailAddresses;
private Address address;
public static class Address {
private String street;
private String city;
}
// + Getters and setters
}
Contact
lördag 24 januari 15

8.
String data = contact.getName();
data += "," + contact.getYearOfBirth();
String[] parts = data.split(",");
contact.setName(parts[0]);
contact.setYearOfBirth(Integer.parseInt(parts[1]));
String conversion
lördag 24 januari 15

9.
String data = contact.getName();
data += "," + contact.getYearOfBirth();
String[] parts = data.split(",");
contact.setName(parts[0]);
contact.setYearOfBirth(Integer.parseInt(parts[1]));
String conversion
lördag 24 januari 15

10.
{
name: "John Doe",
yearOfBirth: 1900,
address: {
street: "Happy Street 1",
city: "Turku"
},
emailAddresses: ["john@doe.com", "johndoe@gmail.com"]
}
JSON
lördag 24 januari 15

11.
JSONObject json = JSONParser.parseStrict(string).isObject();
contact.setName(json.get("name").isString().stringValue());
contact.setYearOfBirth(
(int) json.get("yearOfBirth").isNumber().doubleValue());
contact.setAddress(
parseAddress(json.get("address").isObject()));
JSONArray emailAddresses =
json.get("emailAddresses").isArray();
for (int i = 0; i < emailAddresses.size(); i++) {
contact.getEmailAddresses().add(
emailAddresses.get(i).isString().stringValue());
}
}
JSONValue parsing
lördag 24 januari 15

12.
Good
• It’s standard
• Human readable
format
• Compact format
Bad
• Not completely
typesafe
• Boilerplate
• Client only
JSONValue
lördag 24 januari 15

13.
What about the
server?
lördag 24 januari 15

14.
ObjectMapper mapper = new ObjectMapper();
try {
Contact contact = mapper.readValue(string, Contact.class);
} catch (VariousExceptions e) {
// Do something sensible
}
Jackson on the server
lördag 24 januari 15

15.
Reflection
Code generation
lördag 24 januari 15

16.
public static interface ContactMapper extends
ObjectMapper<Contact> {}
public Contact parseContact(String string) {
ContactMapper mapper = GWT.create(ContactMapper.class);
Contact contact = mapper.read(jsonString);
return contact;
}
gwt-jackson
lördag 24 januari 15

17.
Good
• Minimal boiler plate
• Can share code
between server and
client
Bad
• Only creating and
reading strings
Jackson
lördag 24 januari 15

18.
Where to send?
lördag 24 januari 15

19.
public interface ContactService {
public void saveContact(Contact contact);
public List<Contact> getContacts();
}
Remote Procedure Call
lördag 24 januari 15

20.
public interface ContactService {
public AsyncResult<Void> saveContact(Contact contact);
public AsyncResult<List<Contact>> getContacts();
}
Asynchronous
public interface ContactServiceAsync {
public void saveContact(Contact contact,
AsyncCallback<Void> callback);
public void getContacts(AsyncCallback<List<Contact>>
callback);
}
lördag 24 januari 15

21.
Good
• Simple but powerful
concept
• The default solution
• Optimized format
Bad
• Sending the entire
object graph
• Polymorphism can
cause huge files
• Optimized format
GWT-RPC
lördag 24 januari 15

22.
Most popular!
51 %
lördag 24 januari 15

23.
Where to send
JSON?
lördag 24 januari 15

24.
GET /contacts
DELETE /contacts/5
PUT /contacts { name: "John Doe", ... }
REST
lördag 24 januari 15

25.
@Path("/contacts")
public interface ContactsService {
@GET
public List<Contact> listContacts();
@Path("/{id}")
@DELETE
public void deleteContact(@PathParam("id") int id);
@PUT
public void createContact(Contact contact);
}
JAX-RS
lördag 24 januari 15

26.
@Path("/contacts")
public interface ContactsService extends DirectRestService {
// Same content
}
ContactsService contactsService =
GWT.create(ContactsService.class);
REST.withCallback(myContactListCallback).
call(contactsService).listContacts();
resty-gwt
lördag 24 januari 15

27.
Good
• Any server
• Any client
Bad
• Some boilerplate
resty-gwt
lördag 24 januari 15

28.
Real world usage
6 %
lördag 24 januari 15

29.
Wild ideas
lördag 24 januari 15

30.
Send interfaces
instead of objects
lördag 24 januari 15

31.
public interface Contact {
public void setName(String name);
public String getName();
public void setYearOfBirth(int yearOfBirth);
public int getYearOfBirth();
public void setAddress(Address address);
public Address getAddress();
public void setEmailAddresses(List<String> addresses);
public List<String> getEmailAddresses();
}
Contact interface
lördag 24 januari 15

32.
New possibilities
Send partial updates
Manage entity identity
Use instance methods for RPC
lördag 24 januari 15

33.
Good
• Entities do not need
to be GWT
compatible
• Combines RPC and
entity management
• Automatic request
handling
Bad
• Complex setup
• Heavy coupling with
the server
RequestFactory
lördag 24 januari 15

34.
Define message
Generate code
lördag 24 januari 15

35.
message Contact {
required string name = 1;
required int32 yearOfBirth = 2;
repeated string emailAddresses = 3;
optional Address address = 4;
}
Contact message
lördag 24 januari 15

36.
Good
• Any language
• Google's data
interchange format
• Backwards
compatible
Bad
• Binary format
• Not very widely
used
Protocol Buffers
lördag 24 januari 15

37.
What if we put
the server in
control?
lördag 24 januari 15

38.
lördag 24 januari 15

39.
public class ContactState extends SharedState {
public String name;
@DelegateToWidget
public int yearOfBirth;
}
@OnStateChange("name")
private void updateName() {
doSomethingWithTheName(getState().name);
}
@Override
protected ContactState getState() {
return (ContactState) super.getState();
}
State synchronization
lördag 24 januari 15

40.
public interface ContactRpc extends ServerRpc {
public void deleteContact(int id);
}
// Register RPC handler on the server
registerRpc(new ContactRpc() {
@Override
public void deleteContact(int id) {
ContactDAO.deleteById(id);
}
});
// Send RPC from the client
public void sendDelete(int contactId) {
getRpcProxy(ContactRpc.class).deleteContact(contactId);
}
RPC
lördag 24 januari 15

41.
Good
• Stateful server
• Server push
Bad
• Stateful server
• Tied to the
framework
Vaadin Connectors
lördag 24 januari 15

42.
What if we
completely hide
the transport?
lördag 24 januari 15

43.
// Fire event
@Inject
Event<Contact> contactEvent;
public void updateContact(Contact contact) {
contactEvent.fire(contact);
}
// Listen to event
public void contactUpdateObserver(@Observes Contact contact) {
ContactDAO.updateContact(contact);
}
CDI events
lördag 24 januari 15

44.
Good
• Transparent
communication
• Server push
Bad
• Transparent
communication
• Tied to the
framework
Errai Bus
lördag 24 januari 15

45.
Questions?
Answers?
Please rate the talk at
gwtcreate.com/agenda
? leif@vaadin.com
lördag 24 januari 15