ProtobufDecoder Class — netty Architecture

Source Code

codec-protobuf/src/main/java/io/netty/handler/codec/protobuf/ProtobufDecoder.java lines 66–134

@Sharable
public class ProtobufDecoder extends MessageToMessageDecoder<ByteBuf> {

    private static final boolean HAS_PARSER;

    static {
        boolean hasParser = false;
        try {
            // MessageLite.getParserForType() is not available until protobuf 2.5.0.
            MessageLite.class.getDeclaredMethod("getParserForType");
            hasParser = true;
        } catch (Throwable t) {
            // Ignore
        }

        HAS_PARSER = hasParser;
    }

    private final MessageLite prototype;
    private final ExtensionRegistryLite extensionRegistry;

    /**
     * Creates a new instance.
     */
    public ProtobufDecoder(MessageLite prototype) {
        this(prototype, null);
    }

    public ProtobufDecoder(MessageLite prototype, ExtensionRegistry extensionRegistry) {
        this(prototype, (ExtensionRegistryLite) extensionRegistry);
    }

    public ProtobufDecoder(MessageLite prototype, ExtensionRegistryLite extensionRegistry) {
        super(ByteBuf.class);
        this.prototype = ObjectUtil.checkNotNull(prototype, "prototype").getDefaultInstanceForType();
        this.extensionRegistry = extensionRegistry;
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out)
            throws Exception {
        final byte[] array;
        final int offset;
        final int length = msg.readableBytes();
        if (msg.hasArray()) {
            array = msg.array();
            offset = msg.arrayOffset() + msg.readerIndex();
        } else {
            array = ByteBufUtil.getBytes(msg, msg.readerIndex(), length, false);
            offset = 0;
        }

        if (extensionRegistry == null) {
            if (HAS_PARSER) {
                out.add(prototype.getParserForType().parseFrom(array, offset, length));
            } else {
                out.add(prototype.newBuilderForType().mergeFrom(array, offset, length).build());
            }
        } else {
            if (HAS_PARSER) {
                out.add(prototype.getParserForType().parseFrom(
                        array, offset, length, extensionRegistry));
            } else {
                out.add(prototype.newBuilderForType().mergeFrom(
                        array, offset, length, extensionRegistry).build());
            }
        }
    }
}