SimpleChannelPromiseAggregator Class — netty Architecture

Source Code

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2CodecUtil.java lines 261–395

    static final class SimpleChannelPromiseAggregator extends DefaultChannelPromise {
        private final ChannelPromise promise;
        private int expectedCount;
        private int doneCount;
        private Throwable aggregateFailure;
        private boolean doneAllocating;

        SimpleChannelPromiseAggregator(ChannelPromise promise, Channel c, EventExecutor e) {
            super(c, e);
            assert promise != null && !promise.isDone();
            this.promise = promise;
        }

        /**
         * Allocate a new promise which will be used to aggregate the overall success of this promise aggregator.
         * @return A new promise which will be aggregated.
         * {@code null} if {@link #doneAllocatingPromises()} was previously called.
         */
        public ChannelPromise newPromise() {
            assert !doneAllocating : "Done allocating. No more promises can be allocated.";
            ++expectedCount;
            return this;
        }

        /**
         * Signify that no more {@link #newPromise()} allocations will be made.
         * The aggregation can not be successful until this method is called.
         * @return The promise that is the aggregation of all promises allocated with {@link #newPromise()}.
         */
        public ChannelPromise doneAllocatingPromises() {
            if (!doneAllocating) {
                doneAllocating = true;
                if (doneCount == expectedCount || expectedCount == 0) {
                    return setPromise();
                }
            }
            return this;
        }

        @Override
        public boolean tryFailure(Throwable cause) {
            if (allowFailure()) {
                ++doneCount;
                setAggregateFailure(cause);
                if (allPromisesDone()) {
                    return tryPromise();
                }
                // TODO: We break the interface a bit here.
                // Multiple failure events can be processed without issue because this is an aggregation.
                return true;
            }
            return false;
        }

        /**
         * Fail this object if it has not already been failed.
         * <p>
         * This method will NOT throw an {@link IllegalStateException} if called multiple times
         * because that may be expected.
         */
        @Override
        public ChannelPromise setFailure(Throwable cause) {
            if (allowFailure()) {
                ++doneCount;
                setAggregateFailure(cause);
                if (allPromisesDone()) {
                    return setPromise();
                }
            }
            return this;
        }

        @Override
        public ChannelPromise setSuccess(Void result) {
            if (awaitingPromises()) {
                ++doneCount;
                if (allPromisesDone()) {
                    setPromise();
                }
            }
            return this;