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

Transport
lördag 24 januari 15

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

Good
• It just works
Bad
• Low level
RequestBuilder
lördag 24 januari 15

Real world usage
8 %
lördag 24 januari 15

What to send?
lördag 24 januari 15

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

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

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

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

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

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

What about the
server?
lördag 24 januari 15

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

Reflection
Code generation
lördag 24 januari 15

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

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

Where to send?
lördag 24 januari 15

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

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

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

Most popular!
51 %
lördag 24 januari 15

Where to send
JSON?
lördag 24 januari 15

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

@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

@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

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

Real world usage
6 %
lördag 24 januari 15

Wild ideas
lördag 24 januari 15

Send interfaces
instead of objects
lördag 24 januari 15

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

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

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

Define message
Generate code
lördag 24 januari 15

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

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

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

lördag 24 januari 15

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

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

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

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

// 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

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

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