ProtocolBuffer + MySQL++实现消息反射查询返回数据

come form http://www.cppblog.com/sunicdavy/archive/2011/12/14/162115.html

protobuf反射代码借鉴自陈硕的blog 的 一种自动反射消息类型的 Google Protobuf 网络传输方案  在此表示感谢

这里是proto文件

message QueryAccount

{    

    // in

    required string SQL = 1;

    // out

    optional int64 id = 2;

}

C++实现

   1:  void ReflectionFill( google::protobuf::Message* Msg, const google::protobuf::Descriptor* MsgDescriptor, mysqlpp::Row& RowData )

   2:  {

   3:      using namespace google::protobuf;

   4:   

   5:      // 遍历所有消息成员

   6:      for ( size_t i = 0;i < MsgDescriptor->field_count();i++ )

   7:      {        

   8:          const FieldDescriptor* EachField = MsgDescriptor->field( i );

   9:   

  10:          // 这里假定optinal的是返回值

  11:          if ( !EachField->is_optional() )

  12:              continue;

  13:   

  14:          // sql的列

  15:          std::string FieldName = EachField->name();

  16:              

  17:          // 返回的CPP类型

  18:          switch ( EachField->cpp_type() )

  19:          {

  20:          case FieldDescriptor::CPPTYPE_STRING:

  21:              {

  22:                  std::string Result  = RowData[FieldName.c_str()];

  23:                  Msg->GetReflection()->SetString( Msg, EachField, Result );

  24:              }

  25:              break;

  26:          case FieldDescriptor::CPPTYPE_INT64:

  27:              {

  28:                  // 从列取值

  29:                  __int64 Result = RowData[FieldName.c_str()];

  30:   

  31:                  // 设置消息

  32:                  Msg->GetReflection()->SetInt64( Msg, EachField, Result );

  33:              }

  34:              break;

  35:          }

  36:   

  37:      }

  38:  }

  39:   

  40:   

  41:   

  42:  void ParseMessage( mysqlpp::Connection& SQLConnection, const char* ProtoType, void* Data, size_t Size )

  43:  {

  44:      // 转载请注明来自 战魂小筑http://www.cppblog.com/sunicdavy

  45:      using namespace google::protobuf;

  46:   

  47:      Message* Msg = NULL;

  48:   

  49:      // 通过类型字符串查出消息类型信息

  50:      const Descriptor* MsgDescriptor = DescriptorPool::generated_pool()->FindMessageTypeByName(ProtoType);

  51:      if (MsgDescriptor == NULL )

  52:          return;

  53:   

  54:      // 取消息原型

  55:      const Message* MsgPrototype = MessageFactory::generated_factory()->GetPrototype(MsgDescriptor);

  56:      if (MsgPrototype == NULL )

  57:          return;

  58:   

  59:      // 不能用原型消息哦,要新的

  60:      Msg = MsgPrototype->New();

  61:   

  62:      // 解析数据

  63:      Msg->ParseFromArray( Data, Size );

  64:   

  65:      // 查找SQL指令

  66:      const FieldDescriptor* SQLField = MsgDescriptor->FindFieldByName("SQL");

  67:      if ( SQLField == NULL )

  68:          return;

  69:   

  70:      // 使用反射查出值

  71:      std::string SQLCmd = Msg->GetReflection()->GetString( *Msg, SQLField );

  72:   

  73:      // 进行SQL查询

  74:      mysqlpp::Query query = SQLConnection.query( SQLCmd.c_str() );

  75:   

  76:      // 确认查询有效

  77:      mysqlpp::StoreQueryResult res = query.store();

  78:   

  79:      if (!res)

  80:          return;

  81:   

  82:      // 这里只取第一个消息

  83:      mysqlpp::Row RowData = *res.begin();

  84:   

  85:      // 反射填充消息

  86:      ReflectionFill( Msg, MsgDescriptor, RowData );

  87:   

  88:      // 测试返回数据

  89:      dbsvc::QueryAccount* qamsg = dynamic_cast( Msg );

  90:      __int64 i = qamsg->id();

  91:   

  92:      delete Msg;

  93:  }

  94:   

  95:   

  96:  int main(int argc, char* argv[])

  97:  {    

  98:      mysqlpp::Connection con(false);

  99:   

 100:      con.set_option(new mysqlpp::SetCharsetNameOption("gbk"));

 101:   

 102:   

 103:      if (!con.connect("testdb", "localhost", "root", "123"))

 104:      {

 105:          return -1;

 106:      }

 107:      else

 108:      {

 109:   

 110:          dbsvc::QueryAccount Msg;

 111:          Msg.set_sql("select id from account where username = 'hello'");

 112:          std::string s;

 113:          Msg.SerializeToString( &s );

 114:   

 115:          ParseMessage( con, "dbsvc.QueryAccount", (void*)s.data(), s.size() );

 116:      }

 117:   

 118:      google::protobuf::ShutdownProtobufLibrary();

 119:  }