本篇文章主要介绍上一篇文章中利用protoc命令生成proto文件对应的另外两个文件的过程，
并简单介绍在实际业务中如何使用这两个文件。

先说结论

上一节我们通过下面的命令使得 user.proto

1	protoc --proto_path=. --micro_out=. --go_out=. proto/greeter.proto

生成了如下两个文件

1	user.pb.go user.pb.micro.go

我们现在可以解释为什么会出现这种情况啦。

protoc是一个代码生成的工具，它其实可以生成多种语言对应的文件,包括但是不限于c++,java,js,python,c#,当然也包括Go。
可以根据命令的参数格式发现–go_out实际上就是将生成的go语言的文件放到当前目录。然后–micro_out就是将生成的微服务的文件放到当前目录，所以就生成了上面的两个文件。
具体是怎么生成的呢？先说生成的go文件，这个文件我看了一下其实主要就是对于proto文件中的message进行编写。因为这个message将会是之后服务器和客户端进行通信的对象结构，所以有一些通用的方法，比如结构体定义，string方法等，在后面微服务的时候可以调用它。再说生成的micro文件，这个文件会针对于service中rpc的定义进行展开。会提供客户端和服务器端对应的api。
先说服务器端api的调用和对应api的使用。

type UserHandler interface {
        RegisterUser(context.Context, *RegisterUserReq, *RegisterUserRsp) error
}

func RegisterUserHandler(s server.Server, hdlr UserHandler, opts ...server.HandlerOption) error {
        type user interface {
                RegisterUser(ctx context.Context, in *RegisterUserReq, out *RegisterUserRsp) error
        }
        type User struct {
                user
        }
        h := &userHandler{hdlr}
        return s.Handle(s.NewHandler(&User{h}, opts...))
}

type userHandler struct {
        UserHandler
}

func (h *userHandler) RegisterUser(ctx context.Context, in *RegisterUserReq, out *RegisterUserRsp) error {
        return h.UserHandler.RegisterUser(ctx, in, out)
}

server端api主要要创建一个服务，然后针对于这个服务提供handler方法，对应的handler要实现接口RegisterUser中的方法。

type User struct{}

func(user *User)  RegisterUser(ctx context.Context, req  *proto.RegisterUserReq,  rsp *proto.RegisterUserRsp) (error){
        rsp.Status ="ok"+req.Name
        return nil
}

//创建服务
service := micro.NewService(
                micro.Name("user"),
        )
proto.RegisterUserHandler(service.Server(), new(User))

更详细的代码可以查看后面的main.go
5. 再说客户端的api和对应api的使用
生成的客户端的api如下所示

type UserService interface {
        RegisterUser(ctx context.Context, in *RegisterUserReq, opts ...client.CallOption) (*RegisterUserRsp, error)
}

type userService struct {
        c    client.Client
        name string
}

func NewUserService(name string, c client.Client) UserService{```}

func (c *userService) RegisterUser(ctx context.Context, in *RegisterUserReq, opts ...client.CallOption) (*RegisterUserRsp, error) {···}

所以在我们使用的时候，要首先通过NewUserService得到对应的service,然后调用RegisterUser方法来得到请求结果。


userService := proto.NewUserService("user", service.Client())

// Call the userregister
rsp, err := userService.RegisterUser(context.TODO(), &proto.RegisterUserReq{Name: "John"})

更加详细的代码可以参见后面client.go中的代码。

具体代码

1. user.proto

syntax = "proto3";

service user{
        rpc RegisterUser(RegisterUserReq) returns (RegisterUserRsp){}
}

message RegisterUserReq{
        string name = 1;
}

message RegisterUserRsp{
        string status = 1;
}

2. user.pb.go

// Code generated by protoc-gen-go. DO NOT EDIT.
// versions:
//      protoc-gen-go v1.21.0
//      protoc        v3.11.4
// source: proto/user.proto

package user

import (
        proto "github.com/golang/protobuf/proto"
        protoreflect "google.golang.org/protobuf/reflect/protoreflect"
        protoimpl "google.golang.org/protobuf/runtime/protoimpl"
        reflect "reflect"
        sync "sync"
)

const (
        // Verify that this generated code is sufficiently up-to-date.
        _ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
        // Verify that runtime/protoimpl is sufficiently up-to-date.
        _ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
)

// This is a compile-time assertion that a sufficiently up-to-date version
// of the legacy proto package is being used.
const _ = proto.ProtoPackageIsVersion4

type RegisterUserReq struct {
        state         protoimpl.MessageState
        sizeCache     protoimpl.SizeCache
        unknownFields protoimpl.UnknownFields

        Name string `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
}

func (x *RegisterUserReq) Reset() {
        *x = RegisterUserReq{}
        if protoimpl.UnsafeEnabled {
                mi := &file_proto_user_proto_msgTypes[0]
                ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
                ms.StoreMessageInfo(mi)
        }
}

func (x *RegisterUserReq) String() string {
        return protoimpl.X.MessageStringOf(x)
}

func (*RegisterUserReq) ProtoMessage() {}

func (x *RegisterUserReq) ProtoReflect() protoreflect.Message {
        mi := &file_proto_user_proto_msgTypes[0]
        if protoimpl.UnsafeEnabled && x != nil {
                ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
                if ms.LoadMessageInfo() == nil {
                        ms.StoreMessageInfo(mi)
                }
                return ms
        }
        return mi.MessageOf(x)
}

// Deprecated: Use RegisterUserReq.ProtoReflect.Descriptor instead.
func (*RegisterUserReq) Descriptor() ([]byte, []int) {
        return file_proto_user_proto_rawDescGZIP(), []int{0}
}

func (x *RegisterUserReq) GetName() string {
        if x != nil {
                return x.Name
        }
        return ""
}

type RegisterUserRsp struct {
        state         protoimpl.MessageState
        sizeCache     protoimpl.SizeCache
        unknownFields protoimpl.UnknownFields

        Status string `protobuf:"bytes,1,opt,name=status,proto3" json:"status,omitempty"`
}

func (x *RegisterUserRsp) Reset() {
        *x = RegisterUserRsp{}
        if protoimpl.UnsafeEnabled {
                mi := &file_proto_user_proto_msgTypes[1]
                ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
                ms.StoreMessageInfo(mi)
        }
}

func (x *RegisterUserRsp) String() string {
        return protoimpl.X.MessageStringOf(x)
}

func (*RegisterUserRsp) ProtoMessage() {}

func (x *RegisterUserRsp) ProtoReflect() protoreflect.Message {
        mi := &file_proto_user_proto_msgTypes[1]
        if protoimpl.UnsafeEnabled && x != nil {
                ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
                if ms.LoadMessageInfo() == nil {
                        ms.StoreMessageInfo(mi)
                }
                return ms
        }
        return mi.MessageOf(x)
}

// Deprecated: Use RegisterUserRsp.ProtoReflect.Descriptor instead.
func (*RegisterUserRsp) Descriptor() ([]byte, []int) {
        return file_proto_user_proto_rawDescGZIP(), []int{1}
}

func (x *RegisterUserRsp) GetStatus() string {
        if x != nil {
                return x.Status
        }
        return ""
}

var File_proto_user_proto protoreflect.FileDescriptor

var file_proto_user_proto_rawDesc = []byte{
        0x0a, 0x10, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x2f, 0x75, 0x73, 0x65, 0x72, 0x2e, 0x70, 0x72, 0x6f,
        0x74, 0x6f, 0x22, 0x25, 0x0a, 0x0f, 0x52, 0x65, 0x67, 0x69, 0x73, 0x74, 0x65, 0x72, 0x55, 0x73,
        0x65, 0x72, 0x52, 0x65, 0x71, 0x12, 0x12, 0x0a, 0x04, 0x6e, 0x61, 0x6d, 0x65, 0x18, 0x01, 0x20,
        0x01, 0x28, 0x09, 0x52, 0x04, 0x6e, 0x61, 0x6d, 0x65, 0x22, 0x29, 0x0a, 0x0f, 0x52, 0x65, 0x67,
        0x69, 0x73, 0x74, 0x65, 0x72, 0x55, 0x73, 0x65, 0x72, 0x52, 0x73, 0x70, 0x12, 0x16, 0x0a, 0x06,
        0x73, 0x74, 0x61, 0x74, 0x75, 0x73, 0x18, 0x01, 0x20, 0x01, 0x28, 0x09, 0x52, 0x06, 0x73, 0x74,
         0x69, 0x73, 0x74, 0x65, 0x72, 0x55, 0x73, 0x65, 0x72, 0x52, 0x73, 0x70, 0x12, 0x16, 0x0a, 0x06,
        0x73, 0x74, 0x61, 0x74, 0x75, 0x73, 0x18, 0x01, 0x20, 0x01, 0x28, 0x09, 0x52, 0x06, 0x73, 0x74,
        0x61, 0x74, 0x75, 0x73, 0x32, 0x3c, 0x0a, 0x04, 0x75, 0x73, 0x65, 0x72, 0x12, 0x34, 0x0a, 0x0c,
        0x52, 0x65, 0x67, 0x69, 0x73, 0x74, 0x65, 0x72, 0x55, 0x73, 0x65, 0x72, 0x12, 0x10, 0x2e, 0x52,
        0x65, 0x67, 0x69, 0x73, 0x74, 0x65, 0x72, 0x55, 0x73, 0x65, 0x72, 0x52, 0x65, 0x71, 0x1a, 0x10,
        0x2e, 0x52, 0x65, 0x67, 0x69, 0x73, 0x74, 0x65, 0x72, 0x55, 0x73, 0x65, 0x72, 0x52, 0x73, 0x70,
        0x22, 0x00, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
}

var (
        file_proto_user_proto_rawDescOnce sync.Once
        file_proto_user_proto_rawDescData = file_proto_user_proto_rawDesc
)

func file_proto_user_proto_rawDescGZIP() []byte {
        file_proto_user_proto_rawDescOnce.Do(func() {
                file_proto_user_proto_rawDescData = protoimpl.X.CompressGZIP(file_proto_user_proto_rawDescData)
        })
        return file_proto_user_proto_rawDescData
}

var file_proto_user_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
var file_proto_user_proto_goTypes = []interface{}{
        (*RegisterUserReq)(nil), // 0: RegisterUserReq
        (*RegisterUserRsp)(nil), // 1: RegisterUserRsp
}
var file_proto_user_proto_depIdxs = []int32{
        0, // 0: user.RegisterUser:input_type -> RegisterUserReq
        1, // 1: user.RegisterUser:output_type -> RegisterUserRsp
        1, // [1:2] is the sub-list for method output_type
        0, // [0:1] is the sub-list for method input_type
        0, // [0:0] is the sub-list for extension type_name
        0, // [0:0] is the sub-list for extension extendee
        0, // [0:0] is the sub-list for field type_name
}

func init() { file_proto_user_proto_init() }
func file_proto_user_proto_init() {
        if File_proto_user_proto != nil {
                return
        }
        if !protoimpl.UnsafeEnabled {
                file_proto_user_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
                        switch v := v.(*RegisterUserReq); i {
                        case 0:
                                return &v.state
                        case 1:
                                return &v.sizeCache
                        case 2:
                                return &v.unknownFields
                        default:
                                return nil
                        }
                }
                file_proto_user_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
                        switch v := v.(*RegisterUserRsp); i {
                        case 0:
                                return &v.state
                        case 1:
                                return &v.sizeCache
                        case 2:
                                return &v.unknownFields
                        default:
                                return nil
                        }
                }
                                       }
                }
        }
        type x struct{}
        out := protoimpl.TypeBuilder{
                File: protoimpl.DescBuilder{
                        GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
                        RawDescriptor: file_proto_user_proto_rawDesc,
                        NumEnums:      0,
                        NumMessages:   2,
                        NumExtensions: 0,
                        NumServices:   1,
                },
                GoTypes:           file_proto_user_proto_goTypes,
                DependencyIndexes: file_proto_user_proto_depIdxs,
                MessageInfos:      file_proto_user_proto_msgTypes,
        }.Build()
        File_proto_user_proto = out.File
        file_proto_user_proto_rawDesc = nil
        file_proto_user_proto_goTypes = nil
        file_proto_user_proto_depIdxs = nil
}

3. user.pb.micro.go

// Code generated by protoc-gen-micro. DO NOT EDIT.
// source: proto/user.proto

package user

import (
        fmt "fmt"
        proto "github.com/golang/protobuf/proto"
        math "math"
)

import (
        context "context"
        api "github.com/micro/go-micro/v2/api"
        client "github.com/micro/go-micro/v2/client"
        server "github.com/micro/go-micro/v2/server"
)

// 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.
// A compilation error at this line likely means your copy of the
// proto package needs to be updated.
const _ = proto.ProtoPackageIsVersion3 // please upgrade the proto package

// Reference imports to suppress errors if they are not otherwise used.
var _ api.Endpoint
var _ context.Context
var _ client.Option
var _ server.Option

// Api Endpoints for User service

func NewUserEndpoints() []*api.Endpoint {
        return []*api.Endpoint{}
}

// Client API for User service

type UserService interface {
        RegisterUser(ctx context.Context, in *RegisterUserReq, opts ...client.CallOption) (*RegisterUserRsp, error)
}

type userService struct {
        c    client.Client
        name string
}

func NewUserService(name string, c client.Client) UserService {
        return &userService{
                c:    c,
                name: name,
        }
}

func (c *userService) RegisterUser(ctx context.Context, in *RegisterUserReq, opts ...client.CallOption) (*RegisterUserRsp, error) {
        req := c.c.NewRequest(c.name, "User.RegisterUser", in)
        out := new(RegisterUserRsp)
        err := c.c.Call(ctx, req, out, opts...)
        if err != nil {
                return nil, err
        }
                        return nil, err
        }
        return out, nil
}

// Server API for User service

type UserHandler interface {
        RegisterUser(context.Context, *RegisterUserReq, *RegisterUserRsp) error
}

func RegisterUserHandler(s server.Server, hdlr UserHandler, opts ...server.HandlerOption) error {
        type user interface {
                RegisterUser(ctx context.Context, in *RegisterUserReq, out *RegisterUserRsp) error
        }
        type User struct {
                user
        }
        h := &userHandler{hdlr}
        return s.Handle(s.NewHandler(&User{h}, opts...))
}

type userHandler struct {
        UserHandler
}

func (h *userHandler) RegisterUser(ctx context.Context, in *RegisterUserReq, out *RegisterUserRsp) error {
        return h.UserHandler.RegisterUser(ctx, in, out)
}

4. main.go

package main

import(
        "context"
        micro "github.com/micro/go-micro/v2"
        proto "datatown/proto"
        "fmt"
)

type User struct{

}

func(user *User)  RegisterUser(ctx context.Context, req  *proto.RegisterUserReq,  rsp *proto.RegisterUserRsp) (error){
        rsp.Status ="ok"+req.Name
        return nil
}

func main() {
        // Create a new service. Optionally include some options here.
        service := micro.NewService(
                micro.Name("user"),
        )

        // Init will parse the command line flags.
        service.Init()

        // Register handler
        proto.RegisterUserHandler(service.Server(), new(User))

        // Run the server
        if err := service.Run(); err != nil {
                fmt.Println(err)
        }
}

5. client.go

package main

import(
        "fmt"
        "context"
        micro "github.com/micro/go-micro/v2"
        proto "datatown/proto"
)

func main() {
        // Create a new service
        service := micro.NewService(micro.Name("user.client"))
        // Initialise the client and parse command line flags
        service.Init()

        // Create new user service  client
        userService := proto.NewUserService("user", service.Client())

        // Call the userregister
        rsp, err := userService.RegisterUser(context.TODO(), &proto.RegisterUserReq{Name: "John"})
        if err != nil {
                fmt.Println(err)
        }

        // Print response
        fmt.Println(rsp.Status)
}