[protobuf] Serialize message in C++, parse using Java
I've Google for a day now and could not find full information on the
following problem.
I want to serialize protobuf messages in C++, send them to a JMS
(using activemq-cpp API) and parse in my Java server. Based on what I
found in my searches, here's my C++ function that serializes the
message:
/*
* Serialize given protobuf message and send to Active MQ JMS using
the producer.
*/
void MessageProducer::send( const diva::messaging::Message&
proto_mesg )
{
using namespace google::protobuf::io;
long bufLength = proto_mesg.ByteSize() +
CodedOutputStream::VarintSize32( proto_mesg.ByteSize() );
unsigned char buf[bufLength];
ZeroCopyOutputStream* raw_output = new ArrayOutputStream( buf,
bufLength );
CodedOutputStream* coded_output = new CodedOutputStream(raw_output);
// Prepend the message size to wire message.
coded_output->WriteVarint32( proto_mesg.ByteSize() );
proto_mesg.SerializeToCodedStream(coded_output);
// Create an ACtive JMS message and insert task & module information
in header.
cms::BytesMessage* message = m_session->createBytesMessage();
// Write serialized protobuf message to the JMS message and send.
message->writeBytes( buf, 0, bufLength );
m_producer->send( message );
delete message;
delete coded_output;
delete raw_output;
}
And here's the part in Java that parses teh received messages from
JMS:
// Create a byte array for received message.
BytesMessage receivedMessage =
(BytesMessage)received_message;
logger.info("received message in NAC");
byte[] mesg_bytes = new
byte[(int)receivedMessage.getBodyLength()];
int num_read = receivedMessage.readBytes(mesg_bytes);
if ( num_read != receivedMessage.getBodyLength() ) {
throw new Exception("Error reading message into
byte array");
}
// Create registry for all possible DIVA messages.
ExtensionRegistry er = ExtensionRegistry.newInstance();
DivaBase.registerAllExtensions(er);
// Parse the received message.
diva.messaging.DivaBase.Message m =
diva.messaging.DivaBase.Message.parseFrom( mesg_bytes, er );
Currently, I get
Problem parsing message received in NAC:
com.google.protobuf.InvalidProtocolBufferException: Protocol message
end-group tag did not match expected tag.
Problem parsing message received in NAC: java.lang.ClassCastException:
org.apache.activemq.command.ActiveMQTextMessage cannot be cast to
javax.jms.BytesMessage
errors for each message and cannot see what I'm doing wrong.
Thanks for any comments on the code and/or pointers you might provide.
--
You received this message because you are subscribed to the Google Groups
"Protocol Buffers" group.
To post to this group, send email to proto...@googlegroups.com.
To unsubscribe from this group, send email to
protobuf+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/protobuf?hl=en.
[protobuf] Re: beginner question about extensions
Duh, the solution was simple, I was confused with the repeated entry
fields.
On Aug 11, 5:25 pm, Jun8 wrote:
> myevents::Event e;
> e.set_task_id( taskID );
> e.set_module_name( moduleName );
>
> // Create a status event
> myevents::StatusEvent* se = e.AddExtension( myevents::status_event );
Should be
myevents::StatusEvent* se =
e.MutableExtension(diva::events::status_event);
Now, I can send the event. To test my reception I do
myevents::Event e;
e.ParseFromString(text);
std::cout << "Received event: " << std::endl << e.DebugString() <<
std::endl;
However, this produces
libprotobuf ERROR google/protobuf/message_lite.cc:123] Can't parse
message of type "myevents.Event" because it is missing required
fields: task_id, module_name
Received event:
Received event:
task_id: 1
module_name: "face_detector"
[diva.events.status_event] {
type: MODULE_START
data {
key: "keyframe_width"
value: "360"
}
}
I couldn't figure out the error message, the fields are clearly there.
--
You received this message because you are subscribed to the Google Groups
"Protocol Buffers" group.
To post to this group, send email to proto...@googlegroups.com.
To unsubscribe from this group, send email to
protobuf+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/protobuf?hl=en.
[protobuf] beginner question about extensions
Hi,
I want to implement a hierarchy of events using protobuf.
Specifically, I have a main Event message type. These Events currently
can be either be a StatusEvent or a DetectionEvent. Here's the proto
definitions I came up with:
// A general event, can be thought as base Event class for other event
types.
message Event {
required int64 task_id = 1;
required string module_name = 2; // module that sent the event
extensions 100 to 199;
}
// Extend the base Event with additional types of events.
extend Event {
optional StatusEvent status_event = 100;
optional DetectionEvent detection_event = 101;
}
// A bounding box detected in a frame representing a region of
interest.
message DetectionEvent {
optional int64 frame = 1; // frame number (starting at 1) where
optional int64 time = 2;
optional string label = 3;
}
// Change of status in current module.
message StatusEvent {
enum EventType {
MODULE_START = 1;
MODULE_END = 2;
MODULE_FATAL = 3;
}
required EventType type = 1;
// Optional key-value pairs for data to be passed on.
message Data {
required string key = 1;
required string value = 2;
}
repeated Data data = 2;
}
This compiles with protoc. My problem is, after I create an Event, e,
I don't know how to add an extension event. I though the way to go was
myevents::Event e;
e.set_task_id( taskID );
e.set_module_name( moduleName );
// Create a status event
myevents::StatusEvent* se = e.AddExtension( myevents::status_event );
se->set_type( myevents::StatusEvent::MODULE_START );
myevents::StatusEvent::Data *data = se->add_data();
data->set_key( "frame_width" );
data->set_value( 100 );
When I do this, I get the following compilation error on my protobuf
header file:
‘Add’ is not a member of
‘google::protobuf::internal::MessageTypeTraits’
so clearly this is not the way to go. What is the correct way to do
this? Any help would be much appreciated.
Thanks!
--
You received this message because you are subscribed to the Google Groups
"Protocol Buffers" group.
To post to this group, send email to proto...@googlegroups.com.
To unsubscribe from this group, send email to
protobuf+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/protobuf?hl=en.
