[Java] Protocol Buffer

[DrMaemi]

1. protoc(Protocol Buffer Compiler) 를 이용한 사용법

• Maven 없이 OS-specific proto compiler (protoc) 을 이용해 Protocol Buffer 사용
• protoc 빌드 후 최종 디렉토리 구조

  $ TREE .
  .
  |-- pom.xml
  `-- src
  |-- main
  |   |-- java
  |   |   `-- org
  |   |       `-- example
  |   |           |-- Main.java
  |   |           |-- proto
  |   |           |   |-- AddressBook.java
  |   |           |   |-- AddressBookOrBuilder.java
  |   |           |   |-- AddressBookProtos.java
  |   |           |   |-- Person.java
  |   |           |   `-- PersonOrBuilder.java
  |   |           `-- protobuf
  |   |               `-- addressbook.proto
  |   `-- resources
  `-- test
      `-- java

  1.1. addressbook.proto 작성

• proto 3 문법 - "Protocol Buffers Version 3 Language Specification," protobuf.dev

  
  // Declaration
  syntax = "proto3";
  package tutorial;

import "google/protobuf/timestamp.proto";

// Java declaration option java_multiple_files = true; option java_package = "org.example.proto"; option java_outer_classname = "AddressBookProtos";

// csharp, go, ... declarations

// Messages message Person { string name = 1; int32 id = 2; string email = 3;

enum PhoneType { MOBILE = 0; HOME = 1; WORK = 2; }

message PhoneNumber { string number = 1; PhoneType type = 2; }

repeated PhoneNumber phones = 4; google.protobuf.Timestamp last_updated = 5; }

message AddressBook { repeated Person people = 1; }

## 1.2. OS 에 맞는 protoc 설치 (다운로드, 압축해제, 환경변수 등록)
- ["Downloads," *protobuf.dev*](https://protobuf.dev/downloads/)

## 1.3. protoc 명령어로 컴파일
```bash
SRC_DIR=./src/main/java
PACKAGE_DIR=$SRC_DIR/org/example
protoc -I=$SRC_DIR --java_out=$SRC_DIR $PACKAGE_DIR/protobuf/*.proto

A. 참조

• "Protocol Buffer Basics: Java," protobuf.dev