in guacamole-common/src/main/java/org/apache/guacamole/servlet/GuacamoleHTTPTunnelServlet.java [363:495]
protected abstract GuacamoleTunnel doConnect(HttpServletRequest request)
throws GuacamoleException;
/**
* Called whenever the JavaScript Guacamole client makes a read request.
* This function should in general not be overridden, as it already
* contains a proper implementation of the read operation.
*
* @param request
* The HttpServletRequest associated with the read request received.
*
* @param response
* The HttpServletResponse associated with the write request received.
* Any data to be sent to the client in response to the write request
* should be written to the response body of this HttpServletResponse.
*
* @param tunnelSessionToken
* The tunnel-specific session token of the HTTP tunnel to read from,
* as specified in the read request. This tunnel must have been created
* by a previous call to doConnect().
*
* @throws GuacamoleException
* If an error occurs while handling the read request.
*/
protected void doRead(HttpServletRequest request,
HttpServletResponse response, String tunnelSessionToken)
throws GuacamoleException {
// Get tunnel, ensure tunnel exists
GuacamoleTunnel tunnel = getTunnel(tunnelSessionToken);
// Ensure tunnel is open
if (!tunnel.isOpen())
throw new GuacamoleResourceNotFoundException("Tunnel is closed.");
// Obtain exclusive read access
GuacamoleReader reader = tunnel.acquireReader();
try {
// Note that although we are sending text, Webkit browsers will
// buffer 1024 bytes before starting a normal stream if we use
// anything but application/octet-stream.
response.setContentType("application/octet-stream");
response.setHeader("Cache-Control", "no-cache");
// Get writer for response
Writer out = new BufferedWriter(new OutputStreamWriter(
response.getOutputStream(), "UTF-8"));
// Stream data to response, ensuring output stream is closed
try {
// Deregister tunnel and throw error if we reach EOF without
// having ever sent any data
char[] message = reader.read();
if (message == null)
throw new GuacamoleConnectionClosedException("Tunnel reached end of stream.");
// For all messages, until another stream is ready (we send at least one message)
do {
// Get message output bytes
out.write(message, 0, message.length);
// Flush if we expect to wait
if (!reader.available()) {
out.flush();
response.flushBuffer();
}
// No more messages another stream can take over
if (tunnel.hasQueuedReaderThreads())
break;
} while (tunnel.isOpen() && (message = reader.read()) != null);
// Close tunnel immediately upon EOF
if (message == null) {
deregisterTunnel(tunnelSessionToken);
tunnel.close();
}
// End-of-instructions marker
out.write("0.;");
out.flush();
response.flushBuffer();
}
// Send end-of-stream marker and close tunnel if connection is closed
catch (GuacamoleConnectionClosedException e) {
// Deregister and close
deregisterTunnel(tunnelSessionToken);
tunnel.close();
// End-of-instructions marker
out.write("0.;");
out.flush();
response.flushBuffer();
}
catch (GuacamoleException e) {
// Deregister and close
deregisterTunnel(tunnelSessionToken);
tunnel.close();
throw e;
}
// Always close output stream
finally {
out.close();
}
}
catch (IOException e) {
// Log typically frequent I/O error if desired
logger.debug("Error writing to servlet output stream", e);
// Deregister and close
deregisterTunnel(tunnelSessionToken);
tunnel.close();
}
finally {
tunnel.releaseReader();
}
}