dubbo_message_protocol_header
消息头详解
协议头是16字节的定长数据:
2byte magic:类似java字节码文件里的魔数，用来判断是不是dubbo协议的数据包。魔数是常量0xdabb 1byte 的消息标志位:16-20序列id,21 event,22 two way,23请求或响应标识 1byte 状态，当消息类型为响应时，设置响应状态。24-31位。状态位, 设置请求响应状态，dubbo定义了一些响应的类型。具体类型见com.alibaba.dubbo.remoting.exchange.Response 8byte 消息ID,long类型，32-95位。每一个请求的唯一识别id（由于采用异步通讯的方式，用来把请求request和返回的response对应上） 4byte 消息长度，96-127位。消息体 body 长度, int 类型，即记录Body Content有多少个字节。 解码过程 ExchangeCodec->encode-> encodeRequest
public void encode(Channel channel, ChannelBuffer buffer, Object msg) throws IOException { if (msg instanceof Request) { encodeRequest(channel, buffer, (Request) msg); } else if (msg instanceof Response) { encodeResponse(channel, buffer, (Response) msg); } else { super.encode(channel, buffer, msg); } } protected void encodeRequest(Channel channel, ChannelBuffer buffer, Request req) throws IOException { Serialization serialization = getSerialization(channel); // header. byte[] header = new byte[HEADER_LENGTH]; // set magic number. Bytes.short2bytes(MAGIC, header); // set request and serialization flag. header[2] = (byte) (FLAG_REQUEST | serialization.getContentTypeId()); if (req.isTwoWay()) header[2] |= FLAG_TWOWAY; if (req.isEvent()) header[2] |= FLAG_EVENT; // set request id. Bytes.long2bytes(req.getId(), header, 4); // encode request data. int savedWriteIndex = buffer.writerIndex(); buffer.writerIndex(savedWriteIndex + HEADER_LENGTH); ChannelBufferOutputStream bos = new ChannelBufferOutputStream(buffer); ObjectOutput out = serialization.serialize(channel.getUrl(), bos); if (req.isEvent()) { encodeEventData(channel, out, req.getData()); } else { encodeRequestData(channel, out, req.getData()); } out.flushBuffer(); if (out instanceof Cleanable) { ((Cleanable) out).cleanup(); } bos.flush(); bos.close(); int len = bos.writtenBytes(); checkPayload(channel, len); Bytes.int2bytes(len, header, 12); // write buffer.writerIndex(savedWriteIndex); buffer.writeBytes(header); // write header. buffer.writerIndex(savedWriteIndex + HEADER_LENGTH + len); } 消息体详解
实现源码在DubboCodec.encodeRequestData(Channel channel, ObjectOutput out, Object data)：
protected void encodeRequestData(Channel channel, ObjectOutput out, Object data) throws IOException { RpcInvocation inv = (RpcInvocation) data; out.writeUTF(inv.getAttachment(Constants.DUBBO_VERSION_KEY, DUBBO_VERSION)); out.writeUTF(inv.getAttachment(Constants.PATH_KEY)); out.writeUTF(inv.getAttachment(Constants.VERSION_KEY)); out.writeUTF(inv.getMethodName()); out.writeUTF(ReflectUtils.getDesc(inv.getParameterTypes())); Object[] args = inv.getArguments(); if (args != null) for (int i = 0; i < args.length; i++) { out.writeObject(encodeInvocationArgument(channel, inv, i)); } out.writeObject(inv.getAttachments()); } 版权声明：本文内容由互联网用户自发贡献，该文观点仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请联系我们举报，一经查实，本站将立刻删除。
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