protobuf是一个语言无关、平台无关的序列化协议，由谷歌开源提供。再加上其高性能、存储占用更小等特点，在云原生的应用中越来越广泛。
在C#中主要有两种方法来使用protobuf协议，nuget包分别为Google.Protobuf和protobuf-net，其中Google.Protobuf由谷歌官方提供。本文简要记录和展示Google.Protobuf的使用方法和特点。
项目资料及文档
- 项目官网：https://developers.google.cn/protocol-buffers?hl=zh-cn
- github主页：https://github.com/protocolbuffers/protobuf/
- 官方文档：https://developers.google.cn/protocol-buffers/docs/overview?hl=zh-cn
- 该nuget包支持.NETFramework 4.5、.NETStandard1.1、.net5等
准备工作
需要用到的nuget有如下两个：Google.Protobuf、Google.Protobuf.Tools，其中Google.Protobuf是主类库，运行时要用到。Google.Protobuf.Tools提供了命令行工具，用于根据.proto文件转为目标语言的类型，仅开发时使用，运行时不需要。
本次Demo使用的.proto文件内容如下：
syntax = "proto3";
option cc_enable_arenas = true; package Tccc.Demo.Protobuf; message ErrorLog {
string LogID = 1;
string Context = 2;
string Stack = 3;
}
首先需要根据.proto文件生成目标类型，操作如下：
./google.protobuf.tools\3.19.1\tools\windows_x64\protoc.exe --csharp_out=./generatedCode ./proto/ErrorLog.proto
其中--csharp_out选项是生成C#语言的目标类型，运行protoc.exe -h 查看帮助信息，可以看到还支持一下几种选项：
--proto_path=PATH
--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.
--kotlin_out=OUT_DIR Generate Kotlin file.
--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.
运行上述命令，会根据指定的ErrorLog.proto文件生成ErrorLog.cs文件，文件中就是C#类型ErrorLog。生成的代码中会给此类型增加方法void WriteTo(CodedOutputStream output)和只读属性Parser，接下来进行序列化和反序列化的关键。
生成的ErrorLog类的完整代码：
// <auto-generated>
// Generated by the protocol buffer compiler. DO NOT EDIT!
// source: ProtoFiles/ErrorLog.proto
// </auto-generated>
#pragma warning disable 1591, 0612, 3021
#region Designer generated code using pb = global::Google.Protobuf;
using pbc = global::Google.Protobuf.Collections;
using pbr = global::Google.Protobuf.Reflection;
using scg = global::System.Collections.Generic;
namespace Tccc.Demo.Protobuf { /// <summary>Holder for reflection information generated from ProtoFiles/ErrorLog.proto</summary>
public static partial class ErrorLogReflection { #region Descriptor
/// <summary>File descriptor for ProtoFiles/ErrorLog.proto</summary>
public static pbr::FileDescriptor Descriptor {
get { return descriptor; }
}
private static pbr::FileDescriptor descriptor; static ErrorLogReflection() {
byte[] descriptorData = global::System.Convert.FromBase64String(
string.Concat(
"ChlQcm90b0ZpbGVzL0Vycm9yTG9nLnByb3RvEhJUY2NjLkRlbW8uUHJvdG9i",
"dWYiOQoIRXJyb3JMb2cSDQoFTG9nSUQYASABKAkSDwoHQ29udGV4dBgCIAEo",
"CRINCgVTdGFjaxgDIAEoCUID+AEBYgZwcm90bzM="));
descriptor = pbr::FileDescriptor.FromGeneratedCode(descriptorData,
new pbr::FileDescriptor[] { },
new pbr::GeneratedClrTypeInfo(null, null, new pbr::GeneratedClrTypeInfo[] {
new pbr::GeneratedClrTypeInfo(typeof(global::Tccc.Demo.Protobuf.ErrorLog), global::Tccc.Demo.Protobuf.ErrorLog.Parser, new[]{ "LogID", "Context", "Stack" }, null, null, null, null)
}));
}
#endregion }
#region Messages
public sealed partial class ErrorLog : pb::IMessage<ErrorLog>
#if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
, pb::IBufferMessage
#endif
{
private static readonly pb::MessageParser<ErrorLog> _parser = new pb::MessageParser<ErrorLog>(() => new ErrorLog());
private pb::UnknownFieldSet _unknownFields;
[global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public static pb::MessageParser<ErrorLog> Parser { get { return _parser; } } [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public static pbr::MessageDescriptor Descriptor {
get { return global::Tccc.Demo.Protobuf.ErrorLogReflection.Descriptor.MessageTypes[0]; }
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
pbr::MessageDescriptor pb::IMessage.Descriptor {
get { return Descriptor; }
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public ErrorLog() {
OnConstruction();
} partial void OnConstruction(); [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public ErrorLog(ErrorLog other) : this() {
logID_ = other.logID_;
context_ = other.context_;
stack_ = other.stack_;
_unknownFields = pb::UnknownFieldSet.Clone(other._unknownFields);
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public ErrorLog Clone() {
return new ErrorLog(this);
} /// <summary>Field number for the "LogID" field.</summary>
public const int LogIDFieldNumber = 1;
private string logID_ = "";
[global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public string LogID {
get { return logID_; }
set {
logID_ = pb::ProtoPreconditions.CheckNotNull(value, "value");
}
} /// <summary>Field number for the "Context" field.</summary>
public const int ContextFieldNumber = 2;
private string context_ = "";
[global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public string Context {
get { return context_; }
set {
context_ = pb::ProtoPreconditions.CheckNotNull(value, "value");
}
} /// <summary>Field number for the "Stack" field.</summary>
public const int StackFieldNumber = 3;
private string stack_ = "";
[global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public string Stack {
get { return stack_; }
set {
stack_ = pb::ProtoPreconditions.CheckNotNull(value, "value");
}
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public override bool Equals(object other) {
return Equals(other as ErrorLog);
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public bool Equals(ErrorLog other) {
if (ReferenceEquals(other, null)) {
return false;
}
if (ReferenceEquals(other, this)) {
return true;
}
if (LogID != other.LogID) return false;
if (Context != other.Context) return false;
if (Stack != other.Stack) return false;
return Equals(_unknownFields, other._unknownFields);
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public override int GetHashCode() {
int hash = 1;
if (LogID.Length != 0) hash ^= LogID.GetHashCode();
if (Context.Length != 0) hash ^= Context.GetHashCode();
if (Stack.Length != 0) hash ^= Stack.GetHashCode();
if (_unknownFields != null) {
hash ^= _unknownFields.GetHashCode();
}
return hash;
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public override string ToString() {
return pb::JsonFormatter.ToDiagnosticString(this);
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public void WriteTo(pb::CodedOutputStream output) {
#if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
output.WriteRawMessage(this);
#else
if (LogID.Length != 0) {
output.WriteRawTag(10);
output.WriteString(LogID);
}
if (Context.Length != 0) {
output.WriteRawTag(18);
output.WriteString(Context);
}
if (Stack.Length != 0) {
output.WriteRawTag(26);
output.WriteString(Stack);
}
if (_unknownFields != null) {
_unknownFields.WriteTo(output);
}
#endif
} #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
[global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
void pb::IBufferMessage.InternalWriteTo(ref pb::WriteContext output) {
if (LogID.Length != 0) {
output.WriteRawTag(10);
output.WriteString(LogID);
}
if (Context.Length != 0) {
output.WriteRawTag(18);
output.WriteString(Context);
}
if (Stack.Length != 0) {
output.WriteRawTag(26);
output.WriteString(Stack);
}
if (_unknownFields != null) {
_unknownFields.WriteTo(ref output);
}
}
#endif [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public int CalculateSize() {
int size = 0;
if (LogID.Length != 0) {
size += 1 + pb::CodedOutputStream.ComputeStringSize(LogID);
}
if (Context.Length != 0) {
size += 1 + pb::CodedOutputStream.ComputeStringSize(Context);
}
if (Stack.Length != 0) {
size += 1 + pb::CodedOutputStream.ComputeStringSize(Stack);
}
if (_unknownFields != null) {
size += _unknownFields.CalculateSize();
}
return size;
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public void MergeFrom(ErrorLog other) {
if (other == null) {
return;
}
if (other.LogID.Length != 0) {
LogID = other.LogID;
}
if (other.Context.Length != 0) {
Context = other.Context;
}
if (other.Stack.Length != 0) {
Stack = other.Stack;
}
_unknownFields = pb::UnknownFieldSet.MergeFrom(_unknownFields, other._unknownFields);
} [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
public void MergeFrom(pb::CodedInputStream input) {
#if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
input.ReadRawMessage(this);
#else
uint tag;
while ((tag = input.ReadTag()) != 0) {
switch(tag) {
default:
_unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
break;
case 10: {
LogID = input.ReadString();
break;
}
case 18: {
Context = input.ReadString();
break;
}
case 26: {
Stack = input.ReadString();
break;
}
}
}
#endif
} #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
[global::System.Diagnostics.DebuggerNonUserCodeAttribute]
[global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
uint tag;
while ((tag = input.ReadTag()) != 0) {
switch(tag) {
default:
_unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, ref input);
break;
case 10: {
LogID = input.ReadString();
break;
}
case 18: {
Context = input.ReadString();
break;
}
case 26: {
Stack = input.ReadString();
break;
}
}
}
}
#endif } #endregion } #endregion Designer generated code
序列化操作
public static byte[] Serialize(ErrorLog log)
{
using (MemoryStream output = new MemoryStream())
{
log.WriteTo(output);
return output.ToArray();
}
}
反序列化操作
ErrorLog desErrorLog= ErrorLog.Parser.ParseFrom(data);
使用特点和理解
- protoc.exe是支持生成多语言类型，这对于跨语言的混合编程比较方便。
- 根据上述使用步骤可以看到，必须先使用工具protoc生成目标类型，才能调用序列化和反序列化方法，这有些不符合.net平台的编码习惯。
- 一堆自动生成的C#类在可维护性方面欠佳，当需要调整属性字段时，还要通过工具重新生成，较为麻烦。