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。