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- Enclosing interface:
- WebSocket
 
 public static interface WebSocket.ListenerThe receiving interface ofWebSocket.A WebSocketinvokes methods of the associated listener passing itself as an argument. These methods are invoked in a thread-safe manner, such that the next invocation may start only after the previous one has finished.When data has been received, the WebSocketinvokes a receive method. MethodsonText,onBinary,onPingandonPongmust return aCompletionStagethat completes once the message has been received by the listener. If a listener's method returnsnullrather than aCompletionStage,WebSocketwill behave as if the listener returned aCompletionStagethat is already completed normally.An IOExceptionraised inWebSocketwill result in an invocation ofonErrorwith that exception (if the input is not closed). Unless otherwise stated if the listener's method throws an exception or aCompletionStagereturned from a method completes exceptionally, the WebSocket will invokeonErrorwith this exception.- API Note:
- The strict sequential order of invocations from
 WebSockettoListenermeans, in particular, that theListener's methods are treated as non-reentrant. This means thatListenerimplementations do not need to be concerned with possible recursion or the order in which they invokeWebSocket.requestin relation to their processing logic.Careful attention may be required if a listener is associated with more than a single WebSocket. In this case invocations related to different instances ofWebSocketmay not be ordered and may even happen concurrently.CompletionStages returned from the receive methods have nothing to do with the counter of invocations. Namely, aCompletionStagedoes not have to be completed in order to receive more invocations of the listener's methods. Here is an example of a listener that requests invocations, one at a time, until a complete message has been accumulated, then processes the result, and completes theCompletionStage:WebSocket.Listener listener = new WebSocket.Listener() { List<CharSequence> parts = new ArrayList<>(); CompletableFuture<?> accumulatedMessage = new CompletableFuture<>(); public CompletionStage<?> onText(WebSocket webSocket, CharSequence message, boolean last) { parts.add(message); webSocket.request(1); if (last) { processWholeText(parts); parts = new ArrayList<>(); accumulatedMessage.complete(null); CompletionStage<?> cf = accumulatedMessage; accumulatedMessage = new CompletableFuture<>(); return cf; } return accumulatedMessage; } ... }
- Since:
- 11
 
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Method SummaryAll Methods Instance Methods Default Methods Modifier and Type Method Description default CompletionStage<?>onBinary(WebSocket webSocket, ByteBuffer data, boolean last)A binary data has been received.default CompletionStage<?>onClose(WebSocket webSocket, int statusCode, String reason)Receives a Close message indicating the WebSocket's input has been closed.default voidonError(WebSocket webSocket, Throwable error)An error has occurred.default voidonOpen(WebSocket webSocket)AWebSockethas been connected.default CompletionStage<?>onPing(WebSocket webSocket, ByteBuffer message)A Ping message has been received.default CompletionStage<?>onPong(WebSocket webSocket, ByteBuffer message)A Pong message has been received.default CompletionStage<?>onText(WebSocket webSocket, CharSequence data, boolean last)A textual data has been received.
 
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Method Detail- 
onOpendefault void onOpen(WebSocket webSocket) AWebSockethas been connected.This is the initial invocation and it is made once. It is typically used to make a request for more invocations. - Implementation Requirements:
- The default implementation is equivalent to:
 webSocket.request(1);
- Parameters:
- webSocket- the WebSocket that has been connected
 
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onTextdefault CompletionStage<?> onText(WebSocket webSocket, CharSequence data, boolean last) A textual data has been received.Return a CompletionStagewhich will be used by theWebSocketas an indication it may reclaim theCharSequence. Do not access theCharSequenceafter thisCompletionStagehas completed.- Implementation Requirements:
- The default implementation is equivalent to:
 webSocket.request(1); return null;
- Implementation Note:
- The datais always a legal UTF-16 sequence.
- Parameters:
- webSocket- the WebSocket on which the data has been received
- data- the data
- last- whether this invocation completes the message
- Returns:
- a CompletionStagewhich completes when theCharSequencemay be reclaimed; ornullif it may be reclaimed immediately
 
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onBinarydefault CompletionStage<?> onBinary(WebSocket webSocket, ByteBuffer data, boolean last) A binary data has been received.This data is located in bytes from the buffer's position to its limit. Return a CompletionStagewhich will be used by theWebSocketas an indication it may reclaim theByteBuffer. Do not access theByteBufferafter thisCompletionStagehas completed.- Implementation Requirements:
- The default implementation is equivalent to:
 webSocket.request(1); return null;
- Parameters:
- webSocket- the WebSocket on which the data has been received
- data- the data
- last- whether this invocation completes the message
- Returns:
- a CompletionStagewhich completes when theByteBuffermay be reclaimed; ornullif it may be reclaimed immediately
 
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onPingdefault CompletionStage<?> onPing(WebSocket webSocket, ByteBuffer message) A Ping message has been received.As guaranteed by the WebSocket Protocol, the message consists of not more than 125bytes. These bytes are located from the buffer's position to its limit.Given that the WebSocket implementation will automatically send a reciprocal pong when a ping is received, it is rarely required to send a pong message explicitly when a ping is received. Return a CompletionStagewhich will be used by theWebSocketas a signal it may reclaim theByteBuffer. Do not access theByteBufferafter thisCompletionStagehas completed.- Implementation Requirements:
- The default implementation is equivalent to:
 webSocket.request(1); return null;
- Parameters:
- webSocket- the WebSocket on which the message has been received
- message- the message
- Returns:
- a CompletionStagewhich completes when theByteBuffermay be reclaimed; ornullif it may be reclaimed immediately
 
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onPongdefault CompletionStage<?> onPong(WebSocket webSocket, ByteBuffer message) A Pong message has been received.As guaranteed by the WebSocket Protocol, the message consists of not more than 125bytes. These bytes are located from the buffer's position to its limit.Return a CompletionStagewhich will be used by theWebSocketas a signal it may reclaim theByteBuffer. Do not access theByteBufferafter thisCompletionStagehas completed.- Implementation Requirements:
- The default implementation is equivalent to:
 webSocket.request(1); return null;
- Parameters:
- webSocket- the WebSocket on which the message has been received
- message- the message
- Returns:
- a CompletionStagewhich completes when theByteBuffermay be reclaimed; ornullif it may be reclaimed immediately
 
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onClosedefault CompletionStage<?> onClose(WebSocket webSocket, int statusCode, String reason) Receives a Close message indicating the WebSocket's input has been closed.This is the last invocation from the specified WebSocket. By the time this invocation begins the WebSocket's input will have been closed.A Close message consists of a status code and a reason for closing. The status code is an integer from the range 1000 <= code <= 65535. Thereasonis a string which has a UTF-8 representation not longer than123bytes.If the WebSocket's output is not already closed, the CompletionStagereturned by this method will be used as an indication that the WebSocket's output may be closed. The WebSocket will close its output at the earliest of completion of the returnedCompletionStageor invoking either of thesendCloseorabortmethods.- API Note:
- Returning a CompletionStagethat never completes, effectively disables the reciprocating closure of the output.To specify a custom closure code or reason code the sendClosemethod may be invoked from inside theonCloseinvocation:public CompletionStage<?> onClose(WebSocket webSocket, int statusCode, String reason) { webSocket.sendClose(CUSTOM_STATUS_CODE, CUSTOM_REASON); return new CompletableFuture<Void>(); }
- Implementation Requirements:
- The default implementation of this method returns
 null, indicating that the output should be closed immediately.
- Parameters:
- webSocket- the WebSocket on which the message has been received
- statusCode- the status code
- reason- the reason
- Returns:
- a CompletionStagewhich completes when theWebSocketmay be closed; ornullif it may be closed immediately
 
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onErrordefault void onError(WebSocket webSocket, Throwable error) An error has occurred.This is the last invocation from the specified WebSocket. By the time this invocation begins both the WebSocket's input and output will have been closed. A WebSocket may invoke this method on the associated listener at any time after it has invoked onOpen, regardless of whether or not any invocations have been requested from the WebSocket.If an exception is thrown from this method, resulting behavior is undefined. - Parameters:
- webSocket- the WebSocket on which the error has occurred
- error- the error
 
 
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