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();
}

 

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。

 

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;
}