安装
protoc （The protocol compiler）是由C++写的，支持的 C++、Java、Python、Objective-C、C#、JavaNano、JavaScript、Ruby、PHP 的实现都在 https://github.com/google/protobuf 这个项目中， 例外的是 Go 的实现是在 https://github.com/golang/protobuf 这里。
所以Go 支持 Protocol Buffers的安装需要下面三步：
- Install the standard C++ implementation of protocol buffers from https://developers.google.com/protocol-buffers/ 。如果不想源码编译的话，可以直接下载对应操作系统对应的 protoc https://github.com/google/protobuf/releases， 参考 ： https://github.com/google/protobuf/releases
- Of course, install the Go compiler and tools from https://golang.org/ See https://golang.org/doc/install for details or, if you are using gccgo, follow the instructions at https://golang.org/doc/install/gccgo 安装Go的开发编译环境。
- Grab the code from the repository and install the proto package. The simplest way is to run go get -u github.com/golang/protobuf/{proto,protoc-gen-go}. The compiler plugin, protoc-gen-go, will be installed in $GOBIN, defaulting to $GOPATH/bin. It must be in your $PATH for the protocol compiler, protoc, to find it.通过go get -u github.com/golang/protobuf/{proto,protoc-gen-go} 获得go的插件包，并完成 protoc-gen-go 的编译。protoc-gen-go 默认会编译到 $GOPATH/bin 目录下， 这个目录需要放入$PATH 中，方便 protoc 找到 protoc-gen-go 。
https://github.com/golang/protobuf 这里其实包含两部分功能：
- a 'protocol compiler plugin' that generates Go source files that, once compiled, can access and manage protocol buffers; Protoc编译插件，产生Go的源码。
- a library that implements run-time support for encoding (marshaling), decoding (unmarshaling), and accessing protocol buffers. 运行时支持库，包括编码、解码、访问PB内容的功能库。
使用 protoc
把 proto 文件编译成 go 源码的命令如下：
$ protoc --go_out=./go/ ./proto/helloworld.proto
参考： http://www.cnblogs.com/ghj1976/p/5435565.html
如果我们需要生产 gRPC 使用的代码， 则需要是下面的命令：
$ protoc --go_out=plugins=grpc:./go/ ./proto/helloworld.proto
注意这类表明了 plugins=grpc，
按照这种方式生成的代码，会多 客户端和服务器端的通用代码，方便我们建立客户端和服务器端的服务。
下面是使用helloworld.proto 产生的 grpc 使用的源码， 比不带 grpc的要多一部分代码。
// Code generated by protoc-gen-go.
// source: proto/helloworld.proto
// DO NOT EDIT!
/*
Package helloworld is a generated protocol buffer package.
It is generated from these files:
proto/helloworld.proto
It has these top-level messages:
HelloRequest
HelloReply
*/
package helloworld
import proto "github.com/golang/protobuf/proto"
import fmt "fmt"
import math "math"
import (
context "golang.org/x/net/context"
grpc "google.golang.org/grpc"
)
// Reference imports to suppress errors if they are not otherwise used.
var _ = proto.Marshal
var _ = fmt.Errorf
var _ = math.Inf
// This is a compile-time assertion to ensure that this generated file
// is compatible with the proto package it is being compiled against.
const _ = proto.ProtoPackageIsVersion1
// The request message containing the user's name.
type HelloRequest struct {
Name string `protobuf:"bytes,1,opt,name=name" json:"name,omitempty"`
}
func (m *HelloRequest) Reset() { *m = HelloRequest{} }
func (m *HelloRequest) String() string { return proto.CompactTextString(m) }
func (*HelloRequest) ProtoMessage() {}
func (*HelloRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
// The response message containing the greetings
type HelloReply struct {
Message string `protobuf:"bytes,1,opt,name=message" json:"message,omitempty"`
}
func (m *HelloReply) Reset() { *m = HelloReply{} }
func (m *HelloReply) String() string { return proto.CompactTextString(m) }
func (*HelloReply) ProtoMessage() {}
func (*HelloReply) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{1} }
func init() {
proto.RegisterType((*HelloRequest)(nil), "helloworld.HelloRequest")
proto.RegisterType((*HelloReply)(nil), "helloworld.HelloReply")
}
// Reference imports to suppress errors if they are not otherwise used.
var _ context.Context
var _ grpc.ClientConn
// This is a compile-time assertion to ensure that this generated file
// is compatible with the grpc package it is being compiled against.
const _ = grpc.SupportPackageIsVersion2
// Client API for Greeter service
type GreeterClient interface {
// Sends a greeting
SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error)
}
type greeterClient struct {
cc *grpc.ClientConn
}
func NewGreeterClient(cc *grpc.ClientConn) GreeterClient {
return &greeterClient{cc}
}
func (c *greeterClient) SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error) {
out := new(HelloReply)
err := grpc.Invoke(ctx, "/helloworld.Greeter/SayHello", in, out, c.cc, opts...)
if err != nil {
return nil, err
}
return out, nil
}
// Server API for Greeter service
type GreeterServer interface {
// Sends a greeting
SayHello(context.Context, *HelloRequest) (*HelloReply, error)
}
func RegisterGreeterServer(s *grpc.Server, srv GreeterServer) {
s.RegisterService(&_Greeter_serviceDesc, srv)
}
func _Greeter_SayHello_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
in := new(HelloRequest)
if err := dec(in); err != nil {
return nil, err
}
if interceptor == nil {
return srv.(GreeterServer).SayHello(ctx, in)
}
info := &grpc.UnaryServerInfo{
Server: srv,
FullMethod: "/helloworld.Greeter/SayHello",
}
handler := func(ctx context.Context, req interface{}) (interface{}, error) {
return srv.(GreeterServer).SayHello(ctx, req.(*HelloRequest))
}
return interceptor(ctx, in, info, handler)
}
var _Greeter_serviceDesc = grpc.ServiceDesc{
ServiceName: "helloworld.Greeter",
HandlerType: (*GreeterServer)(nil),
Methods: []grpc.MethodDesc{
{
MethodName: "SayHello",
Handler: _Greeter_SayHello_Handler,
},
},
Streams: []grpc.StreamDesc{},
}
var fileDescriptor0 = []byte{
// 183 bytes of a gzipped FileDescriptorProto
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0x23, 0xa9, 0x75, 0xe2, 0x07, 0x2b, 0x0e, 0x07, 0xb1, 0x03, 0x40, 0x5e, 0x0a, 0x60, 0x5c, 0xc4,
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0x3f, 0x8e, 0x69, 0xfb, 0x00, 0x00, 0x00,
}
protoc-gen-go 的一些特有的参数如下：
命令格式：
protoc --go_out=plugins=grpc,import_path=mypackage:. *.protoimport_prefix=xxx- a prefix that is added onto the beginning of all imports. Useful for things like generating protos in a subdirectory, or regenerating vendored protobufs in-place. import 的前缀，当产生protos在一个子目录时有用。import_path=foo/bar- used as the package if no input files declarego_package. If it contains slashes, everything up to the rightmost slash is ignored.没有定义go_package 时的包名。plugins=plugin1+plugin2- specifies the list of sub-plugins to load. The only plugin in this repo isgrpc. 插件名，这里只有一个插件 grpcMfoo/bar.proto=quux/shme- declares that foo/bar.proto is associated with Go package quux/shme. This is subject to the import_prefix parameter. 定义proto文件跟包的映射关系。
参考资料：
