java - How to determine message type in protobuf so that I can use that type.parsefrom(byte[ ]) -

i trying send protobuf data cpp side java side.

i have multiple message types defined in .proto

on cpp side, have enums every message type , adding buf output follows:

uint8_t* __temp = (uint8_t*)(buf); *__temp++ = (type) >> 8; *__temp = (type) & 0x00ff; 

how 'type' have added buf, can achieve

messagetype parsefrom(byte[] data); 

it not clear exact requirement. assume trying send different types of messages , the receiver should able parse correct object out of received bytes. can done shown in example below:

message message1 {    required string = 1;    required string b = 2; }  message message2 {    required int64 id = 1;    required string data = 2; }     message wrappermessage {     required int64 commonfield = 1;     oneof msg {         message1 m1 = 2;         message2 m2 = 3;     }    } 

basically, wrappermessage object sent on wire wraps message1 or message2 object. on receiving side may parse wrappermessage object first , use hasfield method check if m1 or m2 fields present in wrapped object , parse message1 or message2 object out of it.

"oneof" feature may not available on older version of protobuf compiler.