Protobuf3 系列一第一个Java demo

客官°小女子只卖身不卖艺 2021-06-24 14:37 320阅读 0赞

## 概念 ##

> Protocol buffers are a flexible, efficient, automated mechanism for serializing structured data – think XML, but smaller, faster, and simpler

简单的说， Protobuf3是类似json,xml的数据交换协议，但是它比它们传输的数据更小，传输的速度更快; 跨语言交互，支持大部分主流编程语言

## Demo ##

### Message ###

Protobuf3通过proto文件定义交互的对象，基本的数据结构叫做Message。 以下是本次使用的第一个demo

// 如果使用此注释，则使用proto3; 否则使用proto2
    syntax = "proto3";
    // 生成类的包名
    option java_package = "com.hry.spring.proto.simple";
    //生成的数据访问类的类名，如果没有指定此值，则生成的类名为proto文件名的驼峰命名方法
    option java_outer_classname = "FirstDemo";
    message Demo {  
      int32 id = 1;  
      string name = 2;
      string email = 3;
      repeated int32 mylist = 4; // List列表
    }

repeated : 在java中表示这是一个List列表  
int32, string 分别对应java中的int, String

### 生成Java类 ###

定义后proto，则可以通过官方的工具生成类 [protoc-3.0.0-win32.zip][]

有两种方式生成java类

方法一通过cmd命令：  
protoc参数的意义见下方的ProtoGenerateClass 类注释

D:/tool/protoc/protoc-3.0.0-win32/bin/protoc.exe -I=D:/project/git/spring_boot/protobuf --java_out=d:/tmp D:/project/git\spring_boot/protobuf/src/main/resources/com/hry/spring/proto/simple/*.proto

方法二通过Java类来实现  
封装调用window命令的类

public class Cmd {
        private void writeInputStream2OutputStream(InputStream in, OutputStream out) throws IOException {
            LineNumberReader lnr = new LineNumberReader(new InputStreamReader(in, "UTF-8"));
            PrintWriter pw = new PrintWriter(new OutputStreamWriter(out, "UTF-8"));
            String s;
            while ((s = lnr.readLine()) != null) {
                // 打印信息
                pw.println(s);
            }
            // 关闭输出流
            lnr.close();
            pw.close();
        }
    
        public void execute(List<String> commandList){
            Assert.notNull(commandList, "commandList can't be null!");
            // 如：protoc.exe -I=D:/project/git/spring_boot/protobuf --java_out=d:/tmp D:/project/git\spring_boot/protobuf/src/main/resources/com/hry/spring/proto/simple/person-entity.proto
            ProcessBuilder pb = new ProcessBuilder(commandList);
            // 错误流和输出流合并到一起输出，否则可能因为2个流的某个缓存区满了而导致现场阻塞
            //错误和正确信息合并输出，因为输出有2个，一个是正确，一个错误，着个只要其中有1个无法被实时读取，则可能造成进程阻塞
            pb.redirectErrorStream(true);
            Process p;
            try {
                p = pb.start();
                writeInputStream2OutputStream(p.getInputStream(), System.err);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
    
            int iResult = p.exitValue();
            if(iResult == 0){
                System.out.println(" result = " +p.exitValue() + " execute command success! Command = " + commandList);
    
            }else{
                System.out.println(" result = " +p.exitValue() + " execute command failure! Command = " + commandList);
            }
    
        }
    }

调用cmd类

public class ProtoGenerateClass { 
        // protoc的目录
        private static final String PROTOC_FILE = "D:/tool/protoc/protoc-3.0.0-win32/bin/protoc.exe";
        // specifies a directory in which to look for .proto files when resolving import directives
        private static final String IMPOR_TPROTO = "D:/project/git/spring_boot/protobuf";
        // 生成java类输出目录
        private static final String JAVA_OUT = "d:/tmp";
        // 指定proto文件
        private static final String protos = "D:/project/git/spring_boot/protobuf/src/main/resources/com/hry/spring/proto/simple/*.proto";
    
        public static void main(String[] args) throws IOException {
            List<String> lCommand = new ArrayList<String>();
            lCommand.add(PROTOC_FILE);
            lCommand.add("-I=" + IMPOR_TPROTO );
            lCommand.add("--java_out=" + JAVA_OUT);
            lCommand.add(protos);
    
            Cmd cmd = new Cmd();
            cmd.execute(lCommand);
        }   
    
    }

### 调用Java类 ###

调用上面的方法生[FirstDemo][]类后，由于此类过大，这里不列出，只显示如何调用此类：

public class FirstDemoTest {
    
        @Test
        public void testMyPerson() throws InvalidProtocolBufferException{
             //模拟将对象转成byte[]，方便传输
            FirstDemo.Demo.Builder builder = Demo.newBuilder();
            builder.setId(1);
            builder.setName("name");
            builder.setEmail("hryou0922@126.com");
            Demo person = builder.build();
            System.out.println("before :"+ person.toString());
    
            System.out.println("===========Person Byte==========");
            for(byte b : person.toByteArray()){
                System.out.print(b);
            }
            System.out.println();
            System.out.println(person.toByteString());
            System.out.println("================================");
    
            //模拟接收Byte[]，反序列化成Person类
            byte[] byteArray =person.toByteArray();
            MyPerson p2 = MyPerson.parseFrom(byteArray);
            System.out.println("after :" +p2.toString());
        }
    
    }

打印内容

before :id: 1
    name: "name"
    email: "hryou0922@126.com"
    
    ===========Person Byte==========
    8118411097109101261710411412111111748575050644950544699111109
    <ByteString@73035e27 size=27>
    ================================
    after :id: 1
    name: "name"
    email: "hryou0922@126.com"

## 代码 ##

[github代码][github]

[protoc-3.0.0-win32.zip]: https://github.com/google/protobuf/releases/tag/v3.0.0
[FirstDemo]: https://github.com/hryou0922/spring_boot/tree/master/protobuf/src/main/java/com/hry/spring/proto/simple
[github]: https://github.com/hryou0922/spring_boot/tree/master/protobuf