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参考文献
getting-started
官网pb java介绍
maven protobuf插件
简单入门1
简单入门2

1. protoc编译器下载安装

https://github.com/protocolbuffers/protobuf/releases?page=10

放入.zshrc中配置环境变量

 ~/IdeaProjects/test2/ protoc --version
libprotoc 3.12.1
 ~/IdeaProjects/test2/ 
 ~/IdeaProjects/test2/ protoc -h       
Usage: protoc [OPTION] PROTO_FILES
Parse PROTO_FILES and generate output based on the options given:-IPATH, --proto_path=PATH   Specify the directory in which to search forimports.  May be specified multiple times;directories will be searched in order.  If notgiven, the current working directory is used.If not found in any of the these directories,the --descriptor_set_in descriptors will bechecked for required proto file.--version                   Show version info and exit.-h, --help                  Show this text and exit.--encode=MESSAGE_TYPE       Read a text-format message of the given typefrom standard input and write it in binaryto standard output.  The message type mustbe defined in PROTO_FILES or their imports.--decode=MESSAGE_TYPE       Read a binary message of the given type fromstandard input and write it in text formatto standard output.  The message type mustbe defined in PROTO_FILES or their imports.--decode_raw                Read an arbitrary protocol message fromstandard input and write the raw tag/valuepairs in text format to standard output.  NoPROTO_FILES should be given when using thisflag.--descriptor_set_in=FILES   Specifies a delimited list of FILESeach containing a FileDescriptorSet (aprotocol buffer defined in descriptor.proto).The FileDescriptor for each of the PROTO_FILESprovided will be loaded from theseFileDescriptorSets. If a FileDescriptorappears multiple times, the first occurrencewill be used.-oFILE,                     Writes a FileDescriptorSet (a protocol buffer,--descriptor_set_out=FILE defined in descriptor.proto) containing all ofthe input files to FILE.--include_imports           When using --descriptor_set_out, also includeall dependencies of the input files in theset, so that the set is self-contained.--include_source_info       When using --descriptor_set_out, do not stripSourceCodeInfo from the FileDescriptorProto.This results in vastly larger descriptors thatinclude information about the originallocation of each decl in the source file aswell as surrounding comments.--dependency_out=FILE       Write a dependency output file in the formatexpected by make. This writes the transitiveset of input file paths to FILE--error_format=FORMAT       Set the format in which to print errors.FORMAT may be 'gcc' (the default) or 'msvs'(Microsoft Visual Studio format).--print_free_field_numbers  Print the free field numbers of the messagesdefined in the given proto files. Groups sharethe same field number space with the parent message. Extension ranges are counted as occupied fields numbers.--plugin=EXECUTABLE         Specifies a plugin executable to use.Normally, protoc searches the PATH forplugins, but you may specify additionalexecutables not in the path using this flag.Additionally, EXECUTABLE may be of the formNAME=PATH, in which case the given plugin nameis mapped to the given executable even ifthe executable's own name differs.--cpp_out=OUT_DIR           Generate C++ header and source.--csharp_out=OUT_DIR        Generate C# source file.--java_out=OUT_DIR          Generate Java source file.--js_out=OUT_DIR            Generate JavaScript source.--objc_out=OUT_DIR          Generate Objective C header and source.--php_out=OUT_DIR           Generate PHP source file.--python_out=OUT_DIR        Generate Python source file.--ruby_out=OUT_DIR          Generate Ruby source file.@<filename>                 Read options and filenames from file. If arelative file path is specified, the filewill be searched in the working directory.The --proto_path option will not affect howthis argument file is searched. Content ofthe file will be expanded in the position of@<filename> as in the argument list. Notethat shell expansion is not applied to thecontent of the file (i.e., you cannot usequotes, wildcards, escapes, commands, etc.).Each line corresponds to a single argument,even if it contains spaces.
 ~/IdeaProjects/test2/ 

安装好上面的编译器就可以手动编译proto文件了，但是java程序员肯定是用maven项目的方式使用了，如何操作呢？下面介绍

2. demo项目构建

2.1 pom文件

<?xml version="1.0" encoding="UTF-8"?>
<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.tom</groupId><artifactId>lnacos</artifactId><version>1.0-SNAPSHOT</version><properties><os.detected.classifier>osx-x86_64</os.detected.classifier><maven.compiler.source>1.8</maven.compiler.source><maven.compiler.target>1.8</maven.compiler.target></properties><!-- https://mvnrepository.com/artifact/com.alibaba.nacos/nacos-client --><dependencies><!-- https://mvnrepository.com/artifact/com.alibaba.nacos/nacos-client --><dependency><groupId>com.alibaba.nacos</groupId><artifactId>nacos-client</artifactId><version>1.1.4</version></dependency><dependency><groupId>com.google.protobuf</groupId><artifactId>protobuf-java</artifactId><version>3.12.1</version></dependency><dependency><groupId>com.google.protobuf</groupId><artifactId>protobuf-java-util</artifactId><version>3.12.1</version></dependency></dependencies><build><plugins><plugin><groupId>org.xolstice.maven.plugins</groupId><artifactId>protobuf-maven-plugin</artifactId><version>0.6.1</version><configuration><protocArtifact>com.google.protobuf:protoc:3.12.0:exe:${os.detected.classifier}</protocArtifact><pluginId>proto</pluginId><pluginArtifact>io.grpc:protoc-gen-grpc-java:1.32.1:exe:${os.detected.classifier}</pluginArtifact><protoSourceRoot>src/main/resources/proto3</protoSourceRoot><outputDirectory>src/main/java</outputDirectory><clearOutputDirectory>false</clearOutputDirectory></configuration><executions><execution><goals><goal>compile</goal><goal>test-compile</goal>
<!--                            <goal>compile-custom</goal>--></goals></execution></executions></plugin></plugins></build>
</project>

2.2 mvn clean complie 生成java文件

测试类LProto

package com.tom.model;import com.google.protobuf.util.JsonFormat;import java.util.Arrays;public class LProto {public static void main(String[] args) throws Exception{DemoModel.Demo.Builder builder = DemoModel.Demo.newBuilder();DemoModel.Demo build = builder.setId(123).setName("123").build();byte[] byteArray = build.toByteArray();System.out.println(Arrays.toString(byteArray));System.out.println(byteArray.length);String print = JsonFormat.printer().print(build);System.out.println(print);System.out.println(print.length());}
}

输出

[8, 123, 26, 3, 49, 50, 51]
7
{"id": 123,"name": "123"
}
32

可以看到使用pb压缩后的字段小了很多。

问题1-os.detected.classifier

增加配置

    <properties><os.detected.classifier>osx-x86_64</os.detected.classifier><maven.compiler.source>1.8</maven.compiler.source><maven.compiler.target>1.8</maven.compiler.target></properties>