Protobuf - 语言独立性

到目前为止，我们一直使用 Java 来序列化和反序列化电影院数据。然而，Google Protobuf 提供的关键功能之一是"语言独立性"。在本章中，我们将了解如何使用 Java 进行序列化并使用 Python 进行反序列化。

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

message Theater {
   string name = 1;
   string address = 2;
  
   int32 total_capcity = 3;
   int64 mobile = 4;
   float base_ticket_price = 5;
  
   bool drive_in = 6;
   
   enum PAYMENT_SYSTEM { 
      CASH = 0;
      CREDIT_CARD = 1;
      DEBIT_CARD = 2;
      APP = 3;
   }
   PAYMENT_SYSTEM payment = 7;
   repeated string snacks = 8;
   map<string, int32> movieTicketPrice = 9;
   TheaterOwner owner = 10;
}
message TheaterOwner{
   string name = 1;
   string address = 2;
}

使用 Java 进行序列化

要将 Protobuf 与 Java 结合使用，我们现在必须使用 protoc 二进制文件从此".proto"文件创建所需的类。让我们看看如何做到这一点 −

protoc --java_out=java/src/main/java proto_files heater.proto

上述命令应创建所需的文件，现在我们可以在 Java 代码中使用它。首先，我们将创建一个 writer 来写入 theater 信息 −

package com.tutorialspoint.theater;

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.tutorialspoint.theater.TheaterOuterClass.Theater;
import com.tutorialspoint.theater.TheaterOuterClass.TheaterOwner;
import com.tutorialspoint.theater.TheaterOuterClass.Theater.PAYMENT_SYSTEM;

public class TheaterWriterComplete{
   public static void main(String[] args) throws IOException {
      TheaterOwner owner = TheaterOwner.newBuilder()
         .setName("Anthony Gonsalves")
         .setAddress("513, St Paul Street, West Coast, California")
         .build();
	    
      List<String> snacks = new ArrayList<>();
      snacks.add("Popcorn");
      snacks.add("Coke");
      snacks.add("Chips");
      snacks.add("Soda");
	        
      Map<String, Integer> ticketPrice = new HashMap<>();
      ticketPrice.put("Avengers Endgame", 700);
      ticketPrice.put("Captain America", 200);
      ticketPrice.put("Wonder Woman 1984", 400);
	   
      Theater theater = Theater.newBuilder()
         .setName("Silver Screener")
         .setAddress("212, Maple Street, LA, California")
         .setDriveIn(true)
         .setTotalCapcity(320)
         .setMobile(98234567189L)
         .setBaseTicketPrice(22.45f)
         .setPayment(PAYMENT_SYSTEM.CREDIT_CARD)
         .putAllMovieTicketPrice(ticketPrice)
         .addAllSnacks(snacks)
         .setOwner(owner)
         .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: 
" + theater);
   }
}

现在，编译后，让我们首先执行writer −

> java -cp .	arget\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:
name: "Silver Screener"
address: "212, Maple Street, LA, California"
total_capcity: 320
mobile: 98234567189
base_ticket_price: 22.45
drive_in: true
payment: CREDIT_CARD
snacks: "Popcorn"
snacks: "Coke"
snacks: "Chips"
snacks: "Soda"
movieTicketPrice {
   key: "Avengers Endgame"
   value: 700
}
movieTicketPrice {
   key: "Captain America"
   value: 200
}
movieTicketPrice {
   key: "Wonder Woman 1984"
   value: 400
}
owner {
   name: "Anthony Gonsalves"
   address: "513, St Paul Street, West Coast, California"
}

使用 Python 进行反序列化

接下来，我们将有一个reader(阅读器)来读取theater(剧院)的信息 −

package com.tutorialspoint.theater;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Map;
import com.google.protobuf.DescriptorProtos.FileDescriptorProto;
import com.google.protobuf.Descriptors.FieldDescriptor;
import com.google.protobuf.Descriptors.FileDescriptor;
import com.tutorialspoint.greeting.Greeting.Greet;
import com.tutorialspoint.theater.TheaterOuterClass.Theater;
import com.tutorialspoint.theater.TheaterOuterClass.Theater.Builder;

public class TheaterReaderExplicit {
   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(
            "Name:" + theater.getName() + "
" +
            "Address:" + theater.getAddress() + "
" +
            "Drive_In:" + theater.getDriveIn() + "
" +
            "Total Capacity:" + theater.getTotalCapcity() + "
" +
            "Base Ticket Prices: " + theater.getBaseTicketPrice() + "
" +
            "Owner: " + theater.getOwner() + "
" +
            "Snacks: " + theater.getSnacksList() + "
" +
            "Payment: " + theater.getPayment()
         );
            
         //Map<FieldDescriptor, Object> f = theater.getAllFields();
         System.out.println("List of fields explicitly specified: " + theater.getAllFields());
      }
   }
}

输出

Saving theater information to file: theater_protobuf_output
Saved theater information with following data to disk:
name: "SilverScreen"

要将 Protobuf 与 Python 结合使用，我们现在必须使用 protoc 二进制文件从此 ".proto" 文件创建所需的类。让我们看看如何做到这一点 −

protoc --python_out=python proto_files heater.proto

上述命令应创建所需的文件，现在我们可以在 Python 代码中使用它。现在，让我们编写一个 Python reader −

from proto_files import theater_pb2
from pathlib import Path
path = Path()

filename = str(path.parent.absolute().parent.joinpath("java").joinpath("theater_protobuf_output"));
print("Reading from file: " + filename)

theater = theater_pb2.Theater()

f = open(filename, "rb")
theater.ParseFromString(f.read())
f.close()

print("Read greeting from disk: 
" + str(theater))

我们读取 Java 目录中生成的 theater_protobuf_output 文件。现在，让我们执行代码 −

python theaterReader.py

Reading from file: google-protobuf\java	heater_protobuf_output
Read greeting from disk: 
name: "Silver Screener"
address: "212, Maple Street, LA, California"
total_capcity: 320
mobile: 98234567189
base_ticket_price: 22.45
drive_in: true
payment: CREDIT_CARD
snacks: "Popcorn"
snacks: "Coke"
snacks: "Chips"
snacks: "Soda"
movieTicketPrice {
   key: "Avengers Endgame"
   value: 700
}
movieTicketPrice {
   key: "Captain America"
   value: 200
}
movieTicketPrice {
   key: "Wonder Woman 1984"
   value: 400
}
owner {
   name: "Anthony Gonsalves"
   address: "513, St Paul Street, West Coast, California"
}

因此，正如我们所见，Java 客户端写入的所有值都被我们的 Python 客户端正确地反序列化和读取，这实际上意味着 Protobuf 与语言无关。