- Direct Known Subclasses:
WebsocketEndpoint
onOpen
method, the programmatic
endpoint gains access to the Session
object, to which the developer may add MessageHandler
implementations in order to intercept incoming websocket messages. Each instance of a websocket endpoint is
guaranteed not to be called by more than one thread at a time per active connection.
If deployed as a client endpoint, it will be instantiated once for the single connection to the server.
When deployed as a server endpoint, the implementation uses the
jakarta.websocket.server.ServerEndpointConfig.Configurator#getEndpointInstance
method to obtain the endpoint
instance it will use for each new client connection. If the developer uses the default
jakarta.websocket.server.ServerEndpointConfig.Configurator
, there will be precisely one endpoint instance per
active client connection. Consequently, in this typical case, when implementing/overriding the methods of Endpoint,
the developer is guaranteed that there will be at most one thread calling each endpoint instance at a time.
If the developer provides a custom jakarta.websocket.server.ServerEndpointConfig.Configurator
which overrides
the default policy for endpoint instance creation, for example, using a single Endpoint instance for multiple client
connections, the developer may need to write code that can execute concurrently.
Here is an example of a simple endpoint that echoes any incoming text message back to the sender.
public class EchoServer extends Endpoint {
@Override
public void onOpen(Session session, EndpointConfig config) {
final RemoteEndpoint.Basic remote = session.getBasicRemote();
session.addMessageHandler(String.class, new MessageHandler.Whole<String>() {
public void onMessage(String text) {
try {
remote.sendText("Got your message (" + text + "). Thanks !");
} catch (IOException ioe) {
// handle send failure here
}
}
});
}
}
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
onClose
(Session session, CloseReason closeReason) This method is called immediately prior to the session with the remote peer being closed.void
Developers may implement this method when the web socket session creates some kind of error that is not modeled in the web socket protocol.abstract void
onOpen
(Session session, EndpointConfig config) Developers must implement this method to be notified when a new conversation has just begun.
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Constructor Details
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Endpoint
public Endpoint()
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Method Details
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onOpen
Developers must implement this method to be notified when a new conversation has just begun.Note:
- It is permitted to send messages from this method.
- It is permitted to add
MessageHandler
s from this method. No messages will be mapped to the appropriateMessageHandler
until this method has completed.
- Parameters:
session
- the session that has just been activated.config
- the configuration used to configure this endpoint.
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onClose
This method is called immediately prior to the session with the remote peer being closed. It is called whether the session is being closed because the remote peer initiated a close and sent a close frame, or whether the local websocket container or this endpoint requests to close the session. The developer may take this last opportunity to retrieve session attributes such as the ID, or any application data it holds before it becomes unavailable after the completion of the method. Developers should not attempt to modify the session from within this method, or send new messages from this call as the underlying connection will not be able to send them at this stage.- Parameters:
session
- the session about to be closed.closeReason
- the reason the session was closed.
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onError
Developers may implement this method when the web socket session creates some kind of error that is not modeled in the web socket protocol. This may for example be a notification that an incoming message is too big to handle, or that the incoming message could not be encoded.There are a number of categories of exception that this method is (currently) defined to handle:
- connection problems, for example, a socket failure that occurs before the web socket connection can be
formally closed. These are modeled as
SessionException
s - runtime errors thrown by developer created message handlers calls.
- conversion errors encoding incoming messages before any message handler has been called. These are modeled as
DecodeException
s
- Parameters:
session
- the session in use when the error occurs.thr
- the throwable representing the problem.
- connection problems, for example, a socket failure that occurs before the web socket connection can be
formally closed. These are modeled as
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