Lz4FrameEncoder extends MessageToByteEncoder<ByteBuf> { public ChannelFuture close() { return close(ctx().newPromise()); } Lz4FrameEncoder();  Lz4FrameEncoder(boolean highCompressor);  Lz4FrameEncoder(LZ4Factory factory, boolean highCompressor, int blockSize, Checksum checksum);  Lz4FrameEncoder(LZ4Factory factory, boolean highCompressor, int blockSize,
                           Checksum checksum, int maxEncodeSize); @Override void flush(final ChannelHandlerContext ctx); boolean isClosed(); ChannelFuture close(); ChannelFuture close(final ChannelPromise promise); @Override void close(final ChannelHandlerContext ctx, final ChannelPromise promise); @Override void handlerAdded(ChannelHandlerContext ctx); @Override void handlerRemoved(ChannelHandlerContext ctx);  }
@Test(timeout = 3000) public void writingAfterClosedChannelDoesNotNPE() throws InterruptedException { EventLoopGroup group = new NioEventLoopGroup(2); Channel serverChannel = null; Channel clientChannel = null; final CountDownLatch latch = new CountDownLatch(1); final AtomicReference<Throwable> writeFailCauseRef = new AtomicReference<Throwable>(); try { ServerBootstrap sb = new ServerBootstrap(); sb.group(group); sb.channel(NioServerSocketChannel.class); sb.childHandler(new ChannelInitializer<Channel>() { @Override protected void initChannel(Channel ch) throws Exception { } }); Bootstrap bs = new Bootstrap(); bs.group(group); bs.channel(NioSocketChannel.class); bs.handler(new ChannelInitializer<Channel>() { @Override protected void initChannel(Channel ch) throws Exception { ch.pipeline().addLast(new Lz4FrameEncoder()); } }); serverChannel = sb.bind(new InetSocketAddress(0)).syncUninterruptibly().channel(); clientChannel = bs.connect(serverChannel.localAddress()).syncUninterruptibly().channel(); final Channel finalClientChannel = clientChannel; clientChannel.eventLoop().execute(new Runnable() { @Override public void run() { finalClientChannel.close(); final int size = 27; ByteBuf buf = ByteBufAllocator.DEFAULT.buffer(size, size); finalClientChannel.writeAndFlush(buf.writerIndex(buf.writerIndex() + size)) .addListener(new ChannelFutureListener() { @Override public void operationComplete(ChannelFuture future) throws Exception { try { writeFailCauseRef.set(future.cause()); } finally { latch.countDown(); } } }); } }); latch.await(); Throwable writeFailCause = writeFailCauseRef.get(); assertNotNull(writeFailCause); Throwable writeFailCauseCause = writeFailCause.getCause(); if (writeFailCauseCause != null) { assertThat(writeFailCauseCause, is(not(instanceOf(NullPointerException.class)))); } } finally { if (serverChannel != null) { serverChannel.close(); } if (clientChannel != null) { clientChannel.close(); } group.shutdownGracefully(); } }