PB中扩展嵌套结构

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http://aboutfedora.blogspot.com/2012/10/protobuf-examples-for-c-and-java-1.html

Protobuf Examples for C++ and Java (1)

This sample .proto is taken from http://blog.wolfman.com/articles/2011/11/23/how-to-implement-polymorphic-protocol-buffers-in-java. The groovy is rewritten in Java and C++. Also see example 2

example.proto

package example;option java_outer_classname = "Commands";message BaseCommand {        extensions 100 to max;        enum CommandType {                VERSION = 1;                LOGIN   = 2;        }        required CommandType type = 1;}message Version {        extend BaseCommand {                required Version cmd = 100;        }        required fixed32 protocol = 1;        required fixed32 versions = 2;}message Login {        extend BaseCommand {                required Login cmd = 101;        }        required string username = 1;        required string password = 2;}

example.cpp

#include #include "example.pb.h"using namespace std;using namespace example;int main(){  string sl;  BaseCommand b;#if 0  Version ver;  ver.set_versions(10);  ver.set_protocol(15);    b.MutableExtension(Version::cmd)->set_versions(10);  b.MutableExtension(Version::cmd)->set_protocol(15);  b.set_type( BaseCommand::VERSION);#else  b.set_type( BaseCommand::LOGIN);  b.MutableExtension(Login::cmd)->set_username("rain");  b.MutableExtension(Login::cmd)->set_password("heavy");  #endif  b.SerializeToString(&sl);  printf("%d\n", sl.length());  BaseCommand* bcmd = new BaseCommand();  if (bcmd->ParseFromString(sl))  {    printf("ParsePartialFromString ok\n");  }    printf("%d\n", bcmd->type());  switch(bcmd->type())  {    case BaseCommand::LOGIN:    {      printf("login\n");      printf("%s %s\n", b.MutableExtension(Login::cmd)->username().c_str(), b.MutableExtension(Login::cmd)->password().c_str());      break;    }    case BaseCommand::VERSION:    {      printf("version\n");      printf("%d %d\n", b.MutableExtension(Version::cmd)->versions(), b.MutableExtension(Version::cmd)->protocol());      break;    }    default:      break;  }  return 1;}

example.java

import example.Commands;import example.Commands.BaseCommand;import com.google.protobuf.GeneratedMessage;import com.google.protobuf.ExtensionRegistry;import java.io.IOException; class ProtoBufExample {        // Helper which wraps the BaseCommand around the extension command        static  BaseCommand wrap(BaseCommand.CommandType type, GeneratedMessage.GeneratedExtension extension, Type cmd) {                return BaseCommand.newBuilder().setType(type).setExtension(extension, cmd).build();        }         ExtensionRegistry registry;         ProtoBufExample() {                // we need to register all the extensions and tell the decoder about them                // otherwise the extension will be ignored                registry= ExtensionRegistry.newInstance();                Commands.registerAllExtensions(registry);        }         BaseCommand buildVersion(int v1, int v2) {                Commands.Version vers= Commands.Version.newBuilder().setProtocol(v1).setVersions(v2).build();                // BaseCommand bcmd= BaseCommand.newBuilder().setType(BaseCommand.CommandType.VERSION).setExtension(Commands.Version.cmd, vers).build();                return wrap(BaseCommand.CommandType.VERSION, Commands.Version.cmd, vers);        }         BaseCommand buildLogin(String username, String password) {                Commands.Login l= Commands.Login.newBuilder().setUsername(username).setPassword(password).build();                return wrap(BaseCommand.CommandType.LOGIN, Commands.Login.cmd, l);        }         BaseCommand decodeIt(byte [] ba) {                // use the registry so extensions will be decoded            try{                BaseCommand b=BaseCommand.newBuilder().mergeFrom(ba, registry).build();                return b;            }            catch (IOException e) {                System.out.println("Unable to create  " +e.getMessage());                return buildVersion(0,1);            }        }     public static void main(String[] args) throws Exception {        ProtoBufExample pb= new ProtoBufExample();        BaseCommand b= pb.buildVersion(1234, 5678);        //BaseCommand b= pb.buildLogin("user1", "test");         System.out.println(b);        System.out.println ("size: " + b.toByteArray().length);         BaseCommand decoded= pb.decodeIt(b.toByteArray());         System.out.println ("We got a "+ decoded.getType() +" message");         // We can switch on the CommandType enum and extract the specific command type (extension) we got        switch(decoded.getType()) {        case VERSION:            System.out.println (decoded.getExtension(Commands.Version.cmd));            break;                        case LOGIN:            System.out.println (decoded.getExtension(Commands.Login.cmd));            break;         default:            System.out.println ("Don't know this type");        }    }    }

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