Protobuf - Numbers

Numbers include protobuf types like int32, int64, float, double, which are basic building blocks of Protobuf. It translates to int, long float, double, respectively, in the languages that we use, for example, Java, Python, etc.

Continuing with our theater example, following is the syntax that we need to have to instruct Protobuf that we will be creating numbers −

syntax = "proto3";
package theater;
option java_package = "com.tutorialspoint.theater";

message Theater {
   int32 total_capcity = 3;
   int64 mobile = 4;
   float base_ticket_price = 5;
}

Now our class/message contains numerical attributes. Each of them also has a position which is what Protobuf uses while serialization and deserialization. Each attribute of a member needs to have a unique number assigned.

To use Protobuf, we will now have to use protoc binary to create the required classes from this ".proto" file. Let us see how to do that −

protoc  --java_out=java/src/main/java proto_files\theater.proto

The above command will create the required files and now we can use it in our Java code. First, let's create a writer to write the theater information −

package com.tutorialspoint.theater;

import java.io.FileOutputStream;
import java.io.IOException;
import com.tutorialspoint.theater.TheaterOuterClass.Theater;

public class TheaterWriter{
   public static void main(String[] args) throws IOException {
      Theater theater = Theater.newBuilder()
         .setTotalCapcity(320)
         .setMobile(98234567189L)
         .setBaseTicketPrice(22.45f)
         .build();
		
      String filename = "theater_protobuf_output";
      System.out.println("Saving theater information to file: " + filename);
		
      try(FileOutputStream output = new FileOutputStream(filename)){
         theater.writeTo(output);
      }
      System.out.println("Saved theater information with following data to disk: \n" + theater);
   }
}

Next, we will have a reader to read the theater information −

package com.tutorialspoint.theater;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import com.tutorialspoint.greeting.Greeting.Greet;
import com.tutorialspoint.theater.TheaterOuterClass.Theater;
import com.tutorialspoint.theater.TheaterOuterClass.Theater.Builder;

public class TheaterReader{
   public static void main(String[] args) throws IOException {
      Builder theaterBuilder = Theater.newBuilder();

      String filename = "theater_protobuf_output";
      System.out.println("Reading from file " + filename);
        
      try(FileInputStream input = new FileInputStream(filename)) {
         Theater theater = theaterBuilder.mergeFrom(input).build();
         System.out.println(theater.getBaseTicketPrice());
         System.out.println(theater);
      }
   }
}

Now, post compilation, let us execute the writer first −

> java -cp .\target\protobuf-tutorial-1.0.jar 
com.tutorialspoint.theater.TheaterWriter

Saving theater information to file: theater_protobuf_output
Saved theater information with following data to disk:
total_capcity: 320
mobile: 98234567189
base_ticket_price: 22.45

Now, let us execute the reader to read from the same file −

java -cp .\target\protobuf-tutorial-1.0.jar 
com.tutorialspoint.theater.TheaterReader

Reading from file theater_protobuf_output
22.45
total_capcity: 320
mobile: 98234567189
base_ticket_price: 22.45

So, as we see, we are able to read the serialized int, float, and long by deserializing the binary data to Theater object. In the next chapter, we will look at the Boolean type.

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