netty笔记-protobuf编解码

1.protobuf编解码

public class TestSubscribeReqProto {

    private static byte[] encode(SubscribeReqProto.SubscribeReq req) {
        return req.toByteArray();
    }

    private static SubscribeReqProto.SubscribeReq decode(byte[] body)
            throws InvalidProtocolBufferException {
        return SubscribeReqProto.SubscribeReq.parseFrom(body);
    }

    private static SubscribeReqProto.SubscribeReq createSubscribeReq() {
        SubscribeReqProto.SubscribeReq.Builder builder = SubscribeReqProto.SubscribeReq
                .newBuilder();
        builder.setSubReqID(1);
        builder.setUserName("Lilinfeng");
        builder.setProductName("Netty Book");
        List address = new ArrayList<>();
        address.add("NanJing YuHuaTai");
        address.add("BeiJing LiuLiChang");
        address.add("ShenZhen HongShuLin");
        builder.addAllAddress(address);
        return builder.build();
    }

    /**
     * @param args
     * @throws InvalidProtocolBufferException
     */
    public static void main(String[] args)
            throws InvalidProtocolBufferException {
        SubscribeReqProto.SubscribeReq req = createSubscribeReq();
        System.out.println("Before encode : " + req.toString());
        SubscribeReqProto.SubscribeReq req2 = decode(encode(req));
        System.out.println("After decode : " + req.toString());
        System.out.println("Assert equal : --> " + req2.equals(req));

    }

}

• newBuilder方法用于创建示例
• toByteArray方法用于序列化(编码)
• parseFrom方法用于反序列化(解码)

2. netty中的protobuf编解码

public class SubReqServer {
    public void bind(int port) throws Exception {
        // 配置服务端的NIO线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 100)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer() {
                        @Override
                        public void initChannel(SocketChannel ch) {
                            ch.pipeline().addLast(
                                    new ProtobufVarint32FrameDecoder());
                            ch.pipeline().addLast(
                                    new ProtobufDecoder(
                                            SubscribeReqProto.SubscribeReq
                                                    .getDefaultInstance()));
                            ch.pipeline().addLast(
                                    new ProtobufVarint32LengthFieldPrepender());
                            ch.pipeline().addLast(new ProtobufEncoder());
                            ch.pipeline().addLast(new SubReqServerHandler());
                        }
                    });

            // 绑定端口，同步等待成功
            ChannelFuture f = b.bind(port).sync();

            // 等待服务端监听端口关闭
            f.channel().closeFuture().sync();
        } finally {
            // 优雅退出，释放线程池资源
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                // 采用默认值
            }
        }
        new SubReqServer().bind(port);
    }
}

• ProtobufEncoder：用于对Probuf类型序列化。
• ProtobufVarint32LengthFieldPrepender：用于在序列化的字节数组前加上一个简单的包头，只包含序列化的字节长度。
• ProtobufVarint32FrameDecoder：用于decode前解决半包和粘包问题（利用包头中的包含数组长度来识别半包粘包）
• ProtobufDecoder：反序列化指定的Probuf字节数组为protobuf类型。

下面都看一下

3. ProtobufVarint32LengthFieldPrepender

用于在序列化的字节数组前加上一个简单的包头，只包含序列化的字节长度。

/**
 * BEFORE DECODE (300 bytes)       AFTER DECODE (302 bytes)
 * +---------------+               +--------+---------------+
 * | Protobuf Data |-------------->| Length | Protobuf Data |
 * |  (300 bytes)  |               | 0xAC02 |  (300 bytes)  |
 * +---------------+               +--------+---------------+
 *
 */
@Sharable
public class ProtobufVarint32LengthFieldPrepender extends MessageToByteEncoder {

    @Override
    protected void encode(
            ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) throws Exception {
        int bodyLen = msg.readableBytes();
        int headerLen = CodedOutputStream.computeRawVarint32Size(bodyLen);
        out.ensureWritable(headerLen + bodyLen);

        CodedOutputStream headerOut =
                CodedOutputStream.newInstance(new ByteBufOutputStream(out));
        headerOut.writeRawVarint32(bodyLen);
        headerOut.flush();

        out.writeBytes(msg, msg.readerIndex(), bodyLen);
    }
}

4. ProtobufEncoder

使用toByteArray方法对Protobuf类型序列化。

public class ProtobufEncoder extends MessageToMessageEncoder {
    @Override
    protected void encode(
            ChannelHandlerContext ctx, MessageLiteOrBuilder msg, List