protobuf－java入门指南

简介

protobuf是google提出的一种于语言无关的序列化协议，经常用于RPC之间的通信协议，其具有简单、编解码高效、空间占用率低等特点深受广大用户的喜好，其已经广泛应用于诸多的开源软件中，详情请参考protobuff。

protobuf性能对比图

序列化大小 序列化耗时 具体的数字

安装步骤

window环境

1. 下载protobuf，解压。
2. 下载protobuf-2.5.0-windows.zip。
3. 解压protobuf-2.5.0-windows.zip，把protoc.exe放在Protobuf安装目录下的src里。（其实放哪都可以）
4. 将protoc.exe的位置信息加入到PATH变量中

配置PATH

mac环境

1. 通过brew进行安装，brew install protobuf250

2. protoc --version验证是否安装成功

   
   环境验证

创建maven工程

1. pom文件如下所示，添加对protobuf的依赖，同时在build中添加hadoop-maven-plugins保证在generate-sources的时候生成java源代码。

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.aliyun.sts.sample</groupId>
    <artifactId>sts-sdk-sample</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>sts-sdk-sample</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <actVer>5.22.0</actVer>
        <protobuf.version>2.5.0</protobuf.version>
        <protoc.path>${env.HADOOP_PROTOC_PATH}</protoc.path>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
        
        <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>2.5.0</version>
        </dependency>
    </dependencies>

    <build>

        <plugins>
            <!-- Maven Assembly Plugin -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>2.4.1</version>
                <configuration>
                    <!-- get all project dependencies -->
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                    <!-- MainClass in mainfest make a executable jar -->
                    <archive>
                        <manifest>
                            <mainClass>com.aliyun.sts.sample.OnboardingRequest</mainClass>
                        </manifest>
                    </archive>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <!-- bind to the packaging phase -->
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

                    <plugin>
                        <groupId>org.apache.hadoop</groupId>
                        <artifactId>hadoop-maven-plugins</artifactId>
                        <executions>
                            <execution>
                                <id>compile-protoc</id>
                                <phase>generate-sources</phase>
                                <goals>
                                    <goal>protoc</goal>
                                </goals>
                                <configuration>
                                    <protocVersion>${protobuf.version}</protocVersion>
                                    <protocCommand>${protoc.path}</protocCommand>
                                    <imports>
                                        <param>${basedir}/src/main/java/com/aliyun/sts/sample/proto</param>
                                    </imports>
                                    <source>
                                        <directory>${basedir}/src/main/java/com/aliyun/sts/sample/proto</directory>
                                        <includes>
                                            <include>mobile.proto</include>
                                        </includes>
                                    </source>
                                    <output>${project.build.directory}/generated-sources/java</output>
                                </configuration>
                            </execution>
                        </executions>
                    </plugin>
        </plugins>
    </build>
</project>

1. maven工程组织结构参考下图

   
   工程结构图

2. 构建mobile.proto文件，定义消息类的格式信息。

option java_package = "com.aliyun.sts.sample.proto";
option java_outer_classname = "Mobile";
option java_generate_equals_and_hash = true;

package com.liujianhui;

message MobilePhone{

    required string               brand = 1 ;
    required Hardware          hardware = 2;
    repeated string              software = 3;

}

message Hardware {

    required int32                    rom = 1;
    required int32                    ram = 2;
    required int32                    size = 3 ;

}

4.测试类，完成序列化和反序列化操作

package com.aliyun.sts.sample.proto;

import com.google.protobuf.InvalidProtocolBufferException;

/**
 * Created by liujianhui on 17/5/3.
 */
public class MobieTest {
    public static void main(String[] args) throws InvalidProtocolBufferException {
        Mobile.MobilePhone.Builder builder = Mobile.MobilePhone.newBuilder();
        Mobile.Hardware.Builder hardware = Mobile.Hardware.newBuilder();
        hardware.setRam(2).setRom(16).setSize(5);
        builder.setHardware(hardware)
                .setBrand("Apple")
                .addSoftware("camera")
                .addSoftware("tecent")
                .addSoftware("browser")
                .addSoftware("player");
        byte[] messageBody = builder.build().toByteArray();

        int headerLen = 1;
        byte[] message = new byte[headerLen+messageBody.length];
        message[0] = (byte)messageBody.length;
        System.arraycopy(messageBody, 0,  message, 1, messageBody.length);
        System.out.println("msg len:"+message.length);

        Mobile.MobilePhone phone = Mobile.MobilePhone.parseFrom(messageBody);
        System.out.println("Receive:");
        System.out.println(phone.toString());
    }
}

5.测试结果，首先直接maven clean compile生成相关代码，然后运行MobileTest

msg len:49
Receive:
brand: "Apple"
hardware {
  rom: 16
  ram: 2
  size: 5
}
software: "camera"
software: "tecent"
software: "browser"
software: "player"

6.生成的源代码结构如下图所示

生成的源文件

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参考

• http://blog.csdn.net/antgan/article/details/52103966