protobuff使用小记

大家都说google protobuf很好用，这两天有时间研究了一下，果然很满意；


才开始研究的时候，始终在想一个问题：protobuf里面没有消息头，包长度，如果我有多个消息类型的话，发送方还好说，但是到了接收方，该如何识别接收到的是哪个消息类型呢？苦苦思考良久，发现其实是我的思路原本就不对，其实在发送的时候，把消息头和消息体不要放在一个message里，分开序列化就ok了，费话就不多说了，测试代码如下：

OPlayVideoMsg playVideMsg = OPlayVideoMsg.newBuilder().setPlayurl("http://111.3pg").setPlayspeed(1).build();byte[] bodybytes = playVideMsg.toByteArray();OMsgHead head = OMsgHead.newBuilder().setMsgtype(1).setMsglen(bodybytes.length).setMsgseq(2).build();byte[] headerbytes = head.toByteArray();ByteArrayOutputStream bos = null;DataOutputStream dos = null;try {bos = new ByteArrayOutputStream();dos = new DataOutputStream(bos);dos.writeInt(headerbytes.length);dos.write(headerbytes);dos.write(playVideMsg.toByteArray());// 解析罗byte[] bytes = bos.toByteArray();ByteArrayInputStream bis = null;DataInputStream dis = null;byte[] headbytes;try {bis = new ByteArrayInputStream(bytes);dis = new DataInputStream(bis);int headSize = dis.readInt();System.out.println(String.format("headSize=%d", headSize));headbytes = new byte[headSize];dis.read(headbytes);OMsgHead header = OMsgHead.parseFrom(headbytes);System.out.println("header======>" + header);byte[] parsebodybytes = new byte[header.getMsglen()];dis.readFully(parsebodybytes);if (header.getMsgtype() == 1) {OPlayVideoMsg playVideoMsg = OPlayVideoMsg.parseFrom(parsebodybytes);System.out.println("OPlayVideoMsg======>" + playVideoMsg);}} finally {if (dis != null)dis.close();if (bis != null)bis.close();}} finally {if (dos != null)dos.close();if (bos != null)bos.close();}

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看到35行没，只要解析出头来，就可以继续序列化相应的消息体。

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附上我的proto文件：package msginfo;

option java_package = "com.example.tutorial";message OMsgHead{    required int32 msgtype = 1;    required int32 msgseq = 2;    required int32 msglen = 3;}message OPlayVideoMsg{required string playurl = 2;required int32 playspeed = 3;}message OPlayImageMsg{required string playurl = 2;}

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