Module java.net.http
Package java.net.http

Interface WebSocket

public interface WebSocket
A WebSocket Client.

WebSocket instances are created through WebSocket.Builder.

WebSocket has an input and an output side. These sides are independent from each other. A side can either be open or closed. Once closed, the side remains closed. WebSocket messages are sent through a WebSocket and received through a WebSocket.Listener associated with it. Messages can be sent until the WebSocket's output is closed, and received until the WebSocket's input is closed.

A send method is any of the sendText, sendBinary, sendPing, sendPong and sendClose methods of WebSocket. A send method initiates a send operation and returns a CompletableFuture which completes once the operation has completed. If the CompletableFuture completes normally the operation is considered succeeded. If the CompletableFuture completes exceptionally, the operation is considered failed. An operation that has been initiated but not yet completed is considered pending.

A receive method is any of the onText, onBinary, onPing, onPong and onClose methods of Listener. WebSocket initiates a receive operation by invoking a receive method on the listener. The listener then must return a CompletionStage which completes once the operation has completed.

To control receiving of messages, a WebSocket maintains an internal counter. This counter's value is a number of times the WebSocket has yet to invoke a receive method. While this counter is zero the WebSocket does not invoke receive methods. The counter is incremented by n when request(n) is called. The counter is decremented by one when the WebSocket invokes a receive method. onOpen and onError are not receive methods. WebSocket invokes onOpen prior to any other methods on the listener. WebSocket invokes onOpen at most once. WebSocket may invoke onError at any given time. If the WebSocket invokes onError or onClose, then no further listener's methods will be invoked, no matter the value of the counter. For a newly built WebSocket the counter is zero.

Unless otherwise stated, null arguments will cause methods of WebSocket to throw NullPointerException, similarly, WebSocket will not pass null arguments to methods of Listener. The state of a WebSocket is not changed by the invocations that throw or return a CompletableFuture that completes with one of the NullPointerException, IllegalArgumentException, IllegalStateException exceptions.

WebSocket handles received Ping and Close messages automatically (as per the WebSocket Protocol) by replying with Pong and Close messages. If the listener receives Ping or Close messages, no mandatory actions from the listener are required.

Since:
11

  • Field Details

  • Method Details

    • sendText

      CompletableFuture<WebSocket> sendText(CharSequence data, boolean last)
      Sends textual data with characters from the given character sequence.

      The character sequence must not be modified until the CompletableFuture returned from this method has completed.

      A CompletableFuture returned from this method can complete exceptionally with:

      • IllegalStateException - if there is a pending text or binary send operation or if the previous binary data does not complete the message
      • IOException - if an I/O error occurs, or if the output is closed
      Parameters:
      data - the data
      last - true if this invocation completes the message, false otherwise
      Returns:
      a CompletableFuture that completes, with this WebSocket, when the data has been sent

    • sendBinary

      CompletableFuture<WebSocket> sendBinary(ByteBuffer data, boolean last)
      Sends binary data with bytes from the given buffer.

      The data is located in bytes from the buffer's position to its limit. Upon normal completion of a CompletableFuture returned from this method the buffer will have no remaining bytes. The buffer must not be accessed until after that.

      The CompletableFuture returned from this method can complete exceptionally with:

      • IllegalStateException - if there is a pending text or binary send operation or if the previous textual data does not complete the message
      • IOException - if an I/O error occurs, or if the output is closed
      Parameters:
      data - the data
      last - true if this invocation completes the message, false otherwise
      Returns:
      a CompletableFuture that completes, with this WebSocket, when the data has been sent

    • sendPing

      CompletableFuture<WebSocket> sendPing(ByteBuffer message)
      Sends a Ping message with bytes from the given buffer.

      The message consists of not more than 125 bytes from the buffer's position to its limit. Upon normal completion of a CompletableFuture returned from this method the buffer will have no remaining bytes. The buffer must not be accessed until after that.

      The CompletableFuture returned from this method can complete exceptionally with:

      Parameters:
      message - the message
      Returns:
      a CompletableFuture that completes, with this WebSocket, when the Ping message has been sent

    • sendPong

      CompletableFuture<WebSocket> sendPong(ByteBuffer message)
      Sends a Pong message with bytes from the given buffer.

      The message consists of not more than 125 bytes from the buffer's position to its limit. Upon normal completion of a CompletableFuture returned from this method the buffer will have no remaining bytes. The buffer must not be accessed until after that.

      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.

      The CompletableFuture returned from this method can complete exceptionally with:

      Parameters:
      message - the message
      Returns:
      a CompletableFuture that completes, with this WebSocket, when the Pong message has been sent

    • sendClose

      CompletableFuture<WebSocket> sendClose(int statusCode, String reason)
      Initiates an orderly closure of this WebSocket's output by sending a Close message with the given status code and the reason.

      The statusCode is an integer from the range 1000 <= code <= 4999. Status codes 1002, 1003, 1006, 1007, 1009, 1010, 1012, 1013 and 1015 are illegal. Behaviour in respect to other status codes is implementation-specific. A legal reason is a string that has a UTF-8 representation not longer than 123 bytes.

      A CompletableFuture returned from this method can complete exceptionally with:

      Unless the CompletableFuture returned from this method completes with IllegalArgumentException, or the method throws NullPointerException, the output will be closed.

      If not already closed, the input remains open until a Close message received, or abort is invoked, or an error occurs.

      Parameters:
      statusCode - the status code
      reason - the reason
      Returns:
      a CompletableFuture that completes, with this WebSocket, when the Close message has been sent

    • request

      void request(long n)
      Increments the counter of invocations of receive methods.

      This WebSocket will invoke onText, onBinary, onPing, onPong or onClose methods on the associated listener (i.e. receive methods) up to n more times.

      Parameters:
      n - the number of invocations
      Throws:
      IllegalArgumentException - if n <= 0

    • getSubprotocol

      String getSubprotocol()
      Returns the subprotocol used by this WebSocket.
      Returns:
      the subprotocol, or an empty string if there's no subprotocol

    • isOutputClosed

      boolean isOutputClosed()
      Tells whether this WebSocket's output is closed.

      If this method returns true, subsequent invocations will also return true.

      Returns:
      true if closed, false otherwise

    • isInputClosed

      boolean isInputClosed()
      Tells whether this WebSocket's input is closed.

      If this method returns true, subsequent invocations will also return true.

      Returns:
      true if closed, false otherwise

    • abort

      void abort()
      Closes this WebSocket's input and output abruptly.

      When this method returns both the input and the output will have been closed. Any pending send operations will fail with IOException. Subsequent invocations of abort will have no effect.