Go语言: 生成Protobuf的Service接口

Protobuf 是Google发布的开源编码规范, 官方支持C++/Java/Python等几种语言.

Go语言发布之后, Go的官方团队发布的GoProtobuf也实现了Protobuf支持.

不过GoProtobuf官方版本并没有实现rpc的支持. protoc-gen-go 甚至连 service 的接口也未生成.

如果看过 “JSON-RPC: a tale of interfaces” 文章, 会发现Go语言支持rpc非常容易.

我们现在就开始尝试给GoProtobuf增加rpc的支持.

当然, 第一步是要生成Service接口.

创建 service.go 文件:

// Copyright 2013 <chaishushan{AT}gmail.com>. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package generator

// ServicePlugin produce the Service interface.
type ServicePlugin struct {
    *Generator
}

// Name returns the name of the plugin.
func (p *ServicePlugin) Name() string { return "ServiceInterface" }

// Init is called once after data structures are built but before
// code generation begins.
func (p *ServicePlugin) Init(g *Generator) {
    p.Generator = g
}

// Generate produces the code generated by the plugin for this file.
func (p *ServicePlugin) GenerateImports(file *FileDescriptor) {
    //
}

// Generate generates the Service interface.
func (p *ServicePlugin) Generate(file *FileDescriptor) {
    for _, svc := range file.Service {
        name := CamelCase(*svc.Name)
        p.P("type ", name, " interface {")
        p.In()
        for _, m := range svc.Method {
            method := CamelCase(*m.Name)
            iType := p.ObjectNamed(*m.InputType)
            oType := p.ObjectNamed(*m.OutputType)
            p.P(method, "(in *", p.TypeName(iType), ", out *", p.TypeName(oType), ") error")
        }
        p.Out()
        p.P("}")
    }
}

func init() {
    RegisterPlugin(new(ServicePlugin))
}

将 service.go 文件放到 code.google.com/p/goprotobuf/protoc-gen-go/generator 目录. 重新编译安装 code.google.com/p/goprotobuf/protoc-gen-go.

新建 echo.proto 文件:

// Copyright 2013 <chaishushan{AT}gmail.com>. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package echo;

option cc_generic_services = true;
option java_generic_services = true;
option py_generic_services = true;

message EchoRequest {
    required string message = 1;
}

message EchoResponse {
    required string message = 1;
}

service EchoService {
    rpc echo (EchoRequest) returns (EchoResponse);
}

编译 echo.proto 文件:

protoc --go_out=. echo.proto

生成 echo.pb.go 文件:

// Code generated by protoc-gen-go.
// source: echo.proto
// DO NOT EDIT!

package echo

import proto "code.google.com/p/goprotobuf/proto"
import json "encoding/json"
import math "math"

// Reference proto, json, and math imports to suppress error if they are not otherwise used.
var _ = proto.Marshal
var _ = &json.SyntaxError{}
var _ = math.Inf

type EchoRequest struct {
    Message          *string `protobuf:"bytes,1,req,name=message" json:"message,omitempty"`
    XXX_unrecognized []byte  `json:"-"`
}

func (m *EchoRequest) Reset()         { *m = EchoRequest{} }
func (m *EchoRequest) String() string { return proto.CompactTextString(m) }
func (*EchoRequest) ProtoMessage()    {}

func (m *EchoRequest) GetMessage() string {
    if m != nil && m.Message != nil {
        return *m.Message
    }
    return ""
}

type EchoResponse struct {
    Message          *string `protobuf:"bytes,1,req,name=message" json:"message,omitempty"`
    XXX_unrecognized []byte  `json:"-"`
}

func (m *EchoResponse) Reset()         { *m = EchoResponse{} }
func (m *EchoResponse) String() string { return proto.CompactTextString(m) }
func (*EchoResponse) ProtoMessage()    {}

func (m *EchoResponse) GetMessage() string {
    if m != nil && m.Message != nil {
        return *m.Message
    }
    return ""
}

func init() {
}

type EchoService interface {
    Echo(in *EchoRequest, out *EchoResponse) error
}

注意最后的接口部分是由我们添加的 service.go 生成的:

type EchoService interface {
    Echo(in *EchoRequest, out *EchoResponse) error
}

最基本的准备工作已经完成, 下面就是参考JSON-RPC的例子, 实现一个protobuf版本的rpc了.

下次继续…

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