Getting Started with Protocol Buffers: Serialize and Deserialize Objects in Java

Protocol Buffers (ProtoBuf) is a language‑independent, platform‑independent, extensible method for serializing structured data, offering smaller size (3‑10×) and faster speed (20‑100×) compared with XML.

Defining a .proto file

A .proto file describes the data structures. An example defining a Person message with fields and an enum is shown:

message Person {
    required string name = 1;
    required int32 id = 2;
    optional string email = 3;
    enum PhoneType {
        MOBILE = 0;
        HOME = 1;
        WORK = 2;
    }
    message PhoneNumber {
        required string number = 1;
        optional PhoneType type = 2 [default = HOME];
    }
    repeated PhoneNumber phone = 4;
}

In protobuf‑3 the required and optional keywords are removed; fields are defined with a type, name, and numeric tag.

Compiling the .proto file

Download the appropriate protoc compiler from the official GitHub releases page, extract it, and add protoc.exe to the system PATH. Running protoc --java_out=src/main/java src/protobuf/Student.proto generates Java classes in the specified output directory.

Setting up a Java project

Create a Gradle (or Maven) project in IntelliJ IDEA and add the protobuf dependencies:

dependencies {
    compile ([group:'com.google.protobuf', name:'protobuf-java', version:'3.13.0'],
             [group:'com.google.protobuf', name:'protobuf-java-util', version:'3.13.0'])
}

The IDE will download the corresponding JAR files from Maven Central.

Writing the .proto for the example

Create Student.proto under src/main/protobuf with the following content:

syntax = "proto3";
package com.badao.protobuf;
option optimize_for = SPEED;
option java_package = "com.badao.protobuf";
option java_outer_classname = "DataInfo";

message Student {
    string name = 1;
    int32 age = 2;
    string address = 3;
}

The options set the optimization level, the generated Java package, and the outer class name.

Compiling the .proto to Java classes

Run the protoc command in the terminal (the executable is already in PATH):

protoc --java_out=src/main/java src/protobuf/Student.proto

Successful execution creates DataInfo.java containing the Student class.

Serializing and deserializing objects

Write a test class that builds a Student instance, converts it to a byte array, and parses it back:

package com.badao.protobuf;

import com.google.protobuf.InvalidProtocolBufferException;

public class ProtobufTest {
    public static void main(String[] args) throws InvalidProtocolBufferException {
        DataInfo.Student student = DataInfo.Student.newBuilder()
                .setName("公众号:霸道的程序猿")
                .setAge(100)
                .setAddress("中国")
                .build();
        byte[] bytes = student.toByteArray();
        DataInfo.Student student1 = DataInfo.Student.parseFrom(bytes);
        System.out.println(student1.getName());
        System.out.println(student1.getAge());
        System.out.println(student1.getAddress());
    }
}

The code demonstrates that the generated Student class provides toByteArray() for serialization and parseFrom() for deserialization.

Running the main method prints the original field values, confirming successful round‑trip serialization.