AbstractMemcacheObjectEncoder Class — netty Architecture

Source Code

codec-memcache/src/main/java/io/netty/handler/codec/memcache/AbstractMemcacheObjectEncoder.java lines 35–120

@UnstableApi
public abstract class AbstractMemcacheObjectEncoder<M extends MemcacheMessage> extends MessageToMessageEncoder<Object> {

    private boolean expectingMoreContent;

    public AbstractMemcacheObjectEncoder() {
        super(Object.class);
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, Object msg, List<Object> out) throws Exception {
        if (msg instanceof MemcacheMessage) {
            if (expectingMoreContent) {
                throw new IllegalStateException("unexpected message type: " + StringUtil.simpleClassName(msg));
            }

            @SuppressWarnings({ "unchecked", "CastConflictsWithInstanceof" })
            final M m = (M) msg;
            out.add(encodeMessage(ctx, m));
        }

        if (msg instanceof MemcacheContent || msg instanceof ByteBuf || msg instanceof FileRegion) {
            int contentLength = contentLength(msg);
            if (contentLength > 0) {
                out.add(encodeAndRetain(msg));
            } else {
                out.add(Unpooled.EMPTY_BUFFER);
            }

            expectingMoreContent = !(msg instanceof LastMemcacheContent);
        }
    }

    @Override
    public boolean acceptOutboundMessage(Object msg) throws Exception {
        return msg instanceof MemcacheObject || msg instanceof ByteBuf || msg instanceof FileRegion;
    }

    /**
     * Take the given {@link MemcacheMessage} and encode it into a writable {@link ByteBuf}.
     *
     * @param ctx the channel handler context.
     * @param msg the message to encode.
     * @return the {@link ByteBuf} representation of the message.
     */
    protected abstract ByteBuf encodeMessage(ChannelHandlerContext ctx, M msg);

    /**
     * Determine the content length of the given object.
     *
     * @param msg the object to determine the length of.
     * @return the determined content length.
     */
    private static int contentLength(Object msg) {
        if (msg instanceof MemcacheContent) {
            return ((MemcacheContent) msg).content().readableBytes();
        }
        if (msg instanceof ByteBuf) {
            return ((ByteBuf) msg).readableBytes();
        }
        if (msg instanceof FileRegion) {
            return (int) ((FileRegion) msg).count();
        }
        throw new IllegalStateException("unexpected message type: " + StringUtil.simpleClassName(msg));
    }

    /**
     * Encode the content, depending on the object type.
     *
     * @param msg the object to encode.
     * @return the encoded object.
     */
    private static Object encodeAndRetain(Object msg) {
        if (msg instanceof ByteBuf) {
            return ((ByteBuf) msg).retain();
        }
        if (msg instanceof MemcacheContent) {
            return ((MemcacheContent) msg).content().retain();
        }
        if (msg instanceof FileRegion) {
            return ((FileRegion) msg).retain();