Utf8FrameValidator Class — netty Architecture

Source Code

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/Utf8FrameValidator.java lines 26–129

public class Utf8FrameValidator extends ChannelInboundHandlerAdapter {

    private final boolean closeOnProtocolViolation;

    private int fragmentedFramesCount;
    private Utf8Validator utf8Validator;

    public Utf8FrameValidator() {
        this(true);
    }

    public Utf8FrameValidator(boolean closeOnProtocolViolation) {
        this.closeOnProtocolViolation = closeOnProtocolViolation;
    }

    // See https://datatracker.ietf.org/doc/html/rfc6455#section-5.5.
    private static boolean isControlFrame(WebSocketFrame frame) {
        return frame instanceof CloseWebSocketFrame ||
                frame instanceof PingWebSocketFrame ||
                frame instanceof PongWebSocketFrame;
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if (msg instanceof WebSocketFrame) {
            WebSocketFrame frame = (WebSocketFrame) msg;

            try {
                // Processing for possible fragmented messages for text and binary
                // frames
                if (frame.isFinalFragment()) {
                    // Control frames are allowed between fragments
                    // See https://datatracker.ietf.org/doc/html/rfc6455#section-5.5.
                    if (!isControlFrame(frame)) {

                        // Final frame of the sequence.
                        fragmentedFramesCount = 0;

                        // Check text for UTF8 correctness
                        if (frame instanceof TextWebSocketFrame ||
                                (utf8Validator != null && utf8Validator.isChecking())) {
                            // Check UTF-8 correctness for this payload
                            checkUTF8String(frame.content());

                            // This does a second check to make sure UTF-8
                            // correctness for entire text message
                            utf8Validator.finish();
                        }
                    }
                } else {
                    // Not final frame so we can expect more frames in the
                    // fragmented sequence
                    if (fragmentedFramesCount == 0) {
                        // First text or binary frame for a fragmented set
                        if (frame instanceof TextWebSocketFrame) {
                            checkUTF8String(frame.content());
                        }
                    } else {
                        // Subsequent frames - only check if init frame is text
                        if (utf8Validator != null && utf8Validator.isChecking()) {
                            checkUTF8String(frame.content());
                        }
                    }

                    // Increment counter
                    fragmentedFramesCount++;
                }
            } catch (CorruptedWebSocketFrameException e) {
                protocolViolation(ctx, frame, e);
            }
        }

        super.channelRead(ctx, msg);
    }

    private void checkUTF8String(ByteBuf buffer) {
        if (utf8Validator == null) {
            utf8Validator = new Utf8Validator();
        }
        utf8Validator.check(buffer);
    }