JsonObjectDecoder Class — netty Architecture

Source Code

codec-base/src/main/java/io/netty/handler/codec/json/JsonObjectDecoder.java lines 44–237

public class JsonObjectDecoder extends ByteToMessageDecoder {

    private static final int ST_CORRUPTED = -1;
    private static final int ST_INIT = 0;
    private static final int ST_DECODING_NORMAL = 1;
    private static final int ST_DECODING_ARRAY_STREAM = 2;

    private int openBraces;
    private int idx;

    private int lastReaderIndex;

    private int state;
    private boolean insideString;

    private final int maxObjectLength;
    private final boolean streamArrayElements;

    public JsonObjectDecoder() {
        // 1 MB
        this(1024 * 1024);
    }

    public JsonObjectDecoder(int maxObjectLength) {
        this(maxObjectLength, false);
    }

    public JsonObjectDecoder(boolean streamArrayElements) {
        this(1024 * 1024, streamArrayElements);
    }

    /**
     * @param maxObjectLength   maximum number of bytes a JSON object/array may use (including braces and all).
     *                             Objects exceeding this length are dropped and an {@link TooLongFrameException}
     *                             is thrown.
     * @param streamArrayElements   if set to true and the "top level" JSON object is an array, each of its entries
     *                                  is passed through the pipeline individually and immediately after it was fully
     *                                  received, allowing for arrays with "infinitely" many elements.
     *
     */
    public JsonObjectDecoder(int maxObjectLength, boolean streamArrayElements) {
        this.maxObjectLength = checkPositive(maxObjectLength, "maxObjectLength");
        this.streamArrayElements = streamArrayElements;
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        if (state == ST_CORRUPTED) {
            in.skipBytes(in.readableBytes());
            return;
        }

        if (this.idx > in.readerIndex() && lastReaderIndex != in.readerIndex()) {
            this.idx = in.readerIndex() + (idx - lastReaderIndex);
        }

        // index of next byte to process.
        int idx = this.idx;
        int wrtIdx = in.writerIndex();

        if (wrtIdx > maxObjectLength) {
            // buffer size exceeded maxObjectLength; discarding the complete buffer.
            in.skipBytes(in.readableBytes());
            reset();
            throw new TooLongFrameException(
                            "object length exceeds " + maxObjectLength + ": " + wrtIdx + " bytes discarded");
        }

        for (/* use current idx */; idx < wrtIdx; idx++) {
            byte c = in.getByte(idx);
            if (state == ST_DECODING_NORMAL) {
                decodeByte(c, in, idx);

                // All opening braces/brackets have been closed. That's enough to conclude
                // that the JSON object/array is complete.
                if (openBraces == 0) {
                    ByteBuf json = extractObject(ctx, in, in.readerIndex(), idx + 1 - in.readerIndex());
                    if (json != null) {
                        out.add(json);
                    }