上篇文章介绍了如何安装protobuf环境，文章链接如下
【Go】protobuf介绍及安装-CSDN博客
本节介绍protobuf在gRPC中具体如何使用，并编写测试用例
一、Protobuf是如何工作的
.proto文件是protobuf一个重要的文件，它定义了需要序列化数据的结构，当protobuf编译器（protoc）来运行.proto文件时候，编译器将生成所选择的语言的代码，比如你选择go语言，那么就会将.proto转换成对应的go语言代码，对于go来说，编译器会为每个消息类型生成一个pd.go文件，而C++会生成一个.h文件和一个.cc文件。
使用protobuf的3个步骤是：
1. 在.proto文件中定义消息格式。
2. 用protobuf编译器编译.proto文件。
3. 用C++/Java/go等对应的protobuf API来写或者读消息。
二、Protobuf代码测试
在开始代码编写与测试之前，把官网的链接分享给大家，这个看完可以避坑，尤其是版本，示例代码，proto文件格式等。
工具安装及demo测试：Quick start | Go | gRPC
1.定义proto文件
syntax="proto3";
option go_package="./;student"; //关于最后生成的go文件是处在哪个目录哪个包中，.代表在当前目录生成，student代表了生成的go文件的包名是studentservice DemoService {rpc Sender(StudentRequest) returns (StudentResponse){}
}message StudentRequest {string Id = 1;
}message StudentResponse {string result =1;
}message Student {int64 Id = 1; //idstring Name =2; //姓名string No =3; //学号
}2.生成代码
进入proto文件所在目录，cd ~/sourceCode/go/goproject01/src/day34/grpc/proto
<1>执行protoc --go_out=. student.proto
protoc --go_out=. student.proto执行后发现proto目录生成了一个文件：student.pb.go
<2>执行protoc --go-grpc_out=. student.proto，发现命令执行报错如下
cd ~/sourceCode/go/goproject01/src/day34/grpc/proto
protoc --go-grpc_out=. student.proto
protoc-gen-go-grpc: program not found or is not executable
Please specify a program using absolute path or make sure the program is available in your PATH system variable
--go-grpc_out: protoc-gen-go-grpc: Plugin failed with status code 1.
执行报错，发现没有安装protoc-gen-go-grpc，需要安装一下
先执行go get
go get google.golang.org/grpc/cmd/protoc-gen-go-grpc
go: downloading google.golang.org/grpc v1.59.0
go: downloading google.golang.org/grpc/cmd/protoc-gen-go-grpc v1.3.0
go: downloading google.golang.org/protobuf v1.28.1
go: added google.golang.org/grpc/cmd/protoc-gen-go-grpc v1.3.0
go: added google.golang.org/protobuf v1.28.1
再执行go install
go install google.golang.org/grpc/cmd/protoc-gen-go-grpc执行完在$GOBIN目录下生成protoc-gen-go-grpc，源码对应在pkg下
再次执行protoc --go-grpc_out=. student.proto
protoc --go-grpc_out=. student.proto执行后会在当前目录生成一文件：student_grpc.pb.go
<3>执行go mod tidy
打开文件发现依赖的包没有导入，会报错，需要执行一下最小化导入包依赖
go mod tidy
go: finding module for package google.golang.org/grpc
go: finding module for package google.golang.org/grpc/status
go: finding module for package google.golang.org/grpc/codes
go: found google.golang.org/grpc in google.golang.org/grpc v1.59.0
go: found google.golang.org/grpc/codes in google.golang.org/grpc v1.59.0
go: found google.golang.org/grpc/status in google.golang.org/grpc v1.59.0
go: downloading google.golang.org/genproto v0.0.0-20230822172742-b8732ec3820d
go: downloading golang.org/x/text v0.12.0
执行后生成的代码编译通过，不再报错。
3.编写Server端程序
在server包下创建server.go文件
package mainimport ("context""encoding/json""errors""google.golang.org/grpc""google.golang.org/grpc/keepalive"student "goproject01/day34/grpc/proto""log""net""strconv""time"
)// grpc生成源码后多了一个方法mustEmbedUnimplementedDemoServiceServer
// 这个方法首字母小写不允许重载，自定义实现却没法实现该方法，解决方法如下
/**
1，生成代码时候使用选项：
protoc --go_out=. **--go-grpc_opt=require_unimplemented_servers=false** --go-grpc_out=. proto/*.proto
This works, but your binary will fail to compile if you add methods to your service(s) and regenerate/recompile.
That is why we have the embedding requirement by default. We recommend against using this option.
We recommend against using this option（不推荐使用此选项）2，使用内嵌的结构体定义
// server is used to implement helloworld.GreeterServer.
type server struct{
// Embed the unimplemented server
helloworld.UnimplementedGreeterServer
}*/
type MyDemeServiceImpl struct {student.UnimplementedDemoServiceServer
}func (ds *MyDemeServiceImpl) Sender(ctx context.Context, in *student.StudentRequest) (*student.StudentResponse, error) {return handSendMessage(ctx, in)
}func main() {//绑定9091端口listener, err := net.Listen("tcp", ":10005")if err != nil {log.Fatalf("bingding port:9091 error:%v", err)}//注册服务//这个连接最大的空闲时间，超过就释放，解决proxy等到网络问题（不通知grpc的client和server）/**func NewGrpcServer(opts ...grpc.ServerOption) *grpc.Server {var options []grpc.ServerOptionoptions = append(options,grpc.KeepaliveParams(keepalive.ServerParameters{Time: 10 * time.Second, // wait time before ping if no activityTimeout: 20 * time.Second, // ping timeout}),grpc.KeepaliveEnforcementPolicy(keepalive.EnforcementPolicy{MinTime: 60 * time.Second, // min time a client should wait before sending a pingPermitWithoutStream: true,}),grpc.MaxRecvMsgSize(Max_Message_Size),grpc.MaxSendMsgSize(Max_Message_Size),)for _, opt := range opts {if opt != nil {options = append(options, opt)}}return grpc.NewServer(options...)}*/option1 := grpc.KeepaliveParams(keepalive.ServerParameters{MaxConnectionIdle: 5 * time.Minute})option2 := grpc.MaxSendMsgSize(409600) //400kBoption3 := grpc.MaxRecvMsgSize(409600)grpcServer := grpc.NewServer(option1, option2, option3)//impliServer := student.UnimplementedDemoServiceServer{}var impliServer = &MyDemeServiceImpl{}student.RegisterDemoServiceServer(grpcServer, impliServer)log.Printf("server listening at %v", listener.Addr())/*错误的写成http了，导致排查半天err = http.Serve(listener, nil)if err != nil {log.Fatalf("http serve fail:%v", err)}*/if err := grpcServer.Serve(listener); err != nil {panic("error building server: " + err.Error())}
}func handSendMessage(ctx context.Context, req *student.StudentRequest) (*student.StudentResponse, error) {log.Println("receive param=", req.GetId())//模拟根据id查询student对象并构建一个student实例sid := req.GetId()if sid == "" {log.Println("request param id is null")return nil, errors.New("request param id is null")}resp := &student.StudentResponse{}sidInt64, err := strconv.ParseInt(sid, 10, 64)if err != nil {log.Printf("sid:%s covert to int64 error", sid)return nil, errors.New("sid covert to int64 error")}//通过proto进行序列化对象，和原始json以及easyJson使用方法类似s := &student.Student{Name: "xiaoliu", No: "10001", Id: sidInt64}//bytes, errs := proto.Marshal(s) //需要一个指针类型对象bytes, errs := json.Marshal(s)if errs != nil {log.Println("student obj convert to json error")return nil, errors.New("student obj convert to json error")}resp.Result = byteslog.Println("返回客户端序列化字符串：", string(bytes))return resp, nil
}
4.编写客户端程序
package mainimport ("context""flag""google.golang.org/grpc""google.golang.org/grpc/credentials/insecure"student "goproject01/day34/grpc/proto""log""time"
)const (defaultName = "world"defaultId = "10001"
)var (address = flag.String("address", "localhost:10005", "the address connect to ")name = flag.String("name", defaultName, " name to great")id = flag.String("id", defaultId, "id send to server")
)func main() {flag.Parse()connection, err := grpc.Dial(*address, grpc.WithTransportCredentials(insecure.NewCredentials()))if err != nil {log.Fatalf("connect localhost:9091 fail:%v\n", err)}defer connection.Close()client := student.NewDemoServiceClient(connection)ctx, cancel := context.WithTimeout(context.Background(), time.Second*3)defer cancel()resp, errs := client.Sender(ctx, &student.StudentRequest{Id: *id})if errs != nil {log.Fatalf("client call server Sender method fail:%v\n", errs)}//获取StudentResponse result的内容rst := string(resp.GetResult())log.Println("rpc returns result:", rst)}
5.代码测试
<1>启动服务端程序
go run server.go
//启动后打开服务端端口，等待客户端连接日志
2023/12/04 18:24:17 server listening at [::]:10005//启动后接收客户端的参数打印
2023/12/04 18:24:25 receive param= 10001
2023/12/04 18:24:25 返回客户端序列化字符串： {"Id":10001,"Name":"xiaoliu","No":"10001"}
<2>运行客户端程序
go run client.go首次执行发现报错如下：
rpc error: code = Unavailable desc = connection error: desc = "error reading server preface: http2: frame too large"错误解决：自己误把grpc协议写为http，修改代码即可：
/*错误的写成http了，导致排查半天err = http.Serve(listener, nil)if err != nil {log.Fatalf("http serve fail:%v", err)}*/if err := grpcServer.Serve(listener); err != nil {panic("error building server: " + err.Error())}再次执行报错如下：
2023/12/04 18:09:55 client call server Sender method fail:rpc error: code = Internal desc = grpc: error while marshaling: string field contains invalid UTF-8
错误解决：需要修改student.proto文件中StudentResponse的result字段为bytes类型，用来支持utf-8字符。将student.proto文件修改如下：上面的server.go,client.go最终以这个proto文件为准。
syntax="proto3";
option go_package="./;student"; //关于最后生成的go文件是处在哪个目录哪个包中，.代表在当前目录生成，student代表了生成的go文件的包名是studentservice DemoService {rpc Sender(StudentRequest) returns (StudentResponse){}
}message StudentRequest {string Id = 1;
}message StudentResponse {bytes result =1; //涉及到utf-8编码的字符需要使用bytes类型
}message Student {int64 Id = 1; string Name =2;string No =3;
}修改后运行客户端程序：
调用服务端获取序列化的结果如下
go run client.go
2023/12/04 18:24:25 rpc returns result: {"Id":10001,"Name":"xiaoliu","No":"10001"}
6. gRPC官网文档
这里go官网提供使用gRPC开发步骤
Quick start | Go | gRPC
Basics tutorial | Go | gRPC
<1>hellworld测试：examples/helloworld
<2>route_guide测试：examples/route_guide
以上两个测试程序官网都有对应的文档，按照步骤测试执行即可。
7. 补充protobuf定义的数据类型
####
参考资料
gRPC介绍：Basics tutorial | Go | gRPC
Server到Client数据发送过程解析：gRPC 源码分析(四): gRPC server 中 frame 的处理 - 掘金
使用go实现gRPC：墨滴社区
HTTP/2:RFC7540:RFC 7540/7541: Hypertext Transfer Protocol Version 2 (HTTP/2)
