编写 proto 文件
PPG007 ... 2022-5-6 About 3 min
# 编写 proto 文件
# 示例文件
// 指定 Protobuf 的版本。
syntax = "proto3";
// 指明生成 go 代码的包名。
option go_package = "./;pb";
// 对于 Java，将一个 proto 文件编译为多个接口和类。
option java_multiple_files = true;
// 指定生成的 Java 代码的包名。
option java_package = "com.demo.pb";
// 引入其他 proto 文件。
import "laptop_message.proto";
import "filter_message.proto";
// 使用 message 关键字定义一个普通变量。
message CreateLaptopRequest {
Laptop laptop = 1;
}
message CreateLaptopResponse {
string id = 1;
}
message SearchLaptopRequest {
Filter filter = 1;
}
message SearchLaptopResponse {
Laptop laptop = 1;
}
message UploadImageRequest {
// oneof 关键字表示这个 message 中这两种成员同时只能存在一个，代码中会存在覆盖问题。
oneof data {
ImageInfo info =1;
bytes chunk_data = 2;
}
}
message ImageInfo {
string laptop_id = 1;
string image_type = 2;
}
message UploadImageResponse {
string id = 1;
uint32 size = 2;
}
message RateLaptopRequest {
string laptop_id = 1;
double score = 2;
}
message RateLaptopResponse {
string laptop_id = 1;
uint32 rated_count =2;
double average_score = 3;
}
message Laptop {
string id = 1;
string brand = 2;
string name = 3;
CPU cpu = 4;
Memory ram = 5;
// repeated 修饰数组。
repeated GPU gpus = 6;
repeated Storage storeges = 7;
Screen screen = 8;
Keyboard keyboard = 9;
oneof weight {
double weight_kg = 10;
double weight_lb = 11;
}
double price_usd = 12;
uint32 release_year = 13;
google.protobuf.Timestamp updated_at = 14;
}
message Memory {
// 枚举类要以 0 开始。
enum Unit {
UNKNOWN = 0;
BIT = 1;
BYTE = 2;
KILOBYTE = 3;
MEGABYTE = 4;
GIGABYTE = 5;
TERABYTE = 6;
}
uint64 value = 1;
Unit unit = 2;
}
service LaptopService {
// 注意是 returns 不是 return。
// 对于流，使用 stream 关键字修饰。
rpc CreateLaptop(CreateLaptopRequest) returns (CreateLaptopResponse) {};
rpc SearchLaptop (SearchLaptopRequest) returns (stream SearchLaptopResponse) {};
rpc UploadImage (stream UploadImageRequest) returns (UploadImageResponse) {};
rpc RateLaptop (stream RateLaptopRequest) returns (stream RateLaptopResponse) {};
}
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# Extensions
extensions 允许你在 Message 中定义一个区间的字段数值，相当于是在当前文件中尚未被定义的字段的占位符，这允许其他 proto 文件为这个 Message 添加一些字段，下面是一个示例：
example.proto:
syntax = "proto2";
option go_package = "mytest/proto/proto2";
message Foo {
required int64 a = 1;
optional int64 b = 2;
extensions 100 to max;
}
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extensions.proto:
syntax = "proto2";
option go_package = "mytest/proto/proto2";
import "proto2/example.proto";
extend Foo {
optional string c = 100;
}
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最后，通过代码修改值如下：
func main() {
f := proto2.Foo{
A: proto.Int64(123),
B: proto.Int64(456),
}
proto.SetExtension(&f, proto2.E_C.TypeDescriptor().Type(), "test")
log.Println(f.String())
}
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Note
proto3 不支持使用 extensions 关键字。
# custom option
如果想自定义 option,需要引入 google/protobuf/descriptor.proto，这其实就是一个 proto2 编写的 proto 文件：
syntax = "proto3";
option go_package = "mytest/proto/proto3";
import "google/protobuf/descriptor.proto";
extend google.protobuf.FileOptions {
string my_file_option = 50000;
}
extend google.protobuf.MessageOptions {
int32 my_message_option = 50001;
}
extend google.protobuf.FieldOptions {
float my_field_option = 50002;
}
extend google.protobuf.OneofOptions {
int64 my_oneof_option = 50003;
}
extend google.protobuf.EnumOptions {
bool my_enum_option = 50004;
}
extend google.protobuf.EnumValueOptions {
uint32 my_enum_value_option = 50005;
}
extend google.protobuf.ServiceOptions {
MyEnum my_service_option = 50006;
}
extend google.protobuf.MethodOptions {
MyMessage my_method_option = 50007;
}
option (my_file_option) = "Hello world!";
message MyMessage {
option (my_message_option) = 1234;
int32 foo = 1 [(my_field_option) = 4.5];
string bar = 2;
oneof qux {
option (my_oneof_option) = 42;
string quux = 3;
}
}
enum MyEnum {
option (my_enum_option) = true;
FOO = 0 [(my_enum_value_option) = 321];
BAR = 1;
}
message RequestType {}
message ResponseType {}
service MyService {
option (my_service_option) = FOO;
rpc MyMethod(RequestType) returns(ResponseType) {
// Note: my_method_option has type MyMessage. We can set each field
// within it using a separate "option" line.
option (my_method_option).foo = 567;
option (my_method_option).bar = "Some string";
}
}
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读取每一个 option 的示例代码如下：
package main
import (
"encoding/json"
"log"
"mytest/proto/proto3"
"github.com/spf13/cast"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/reflect/protodesc"
)
func main() {
m := proto3.MyMessage{}
f := protodesc.ToFileDescriptorProto(m.ProtoReflect().Descriptor().ParentFile())
log.Println(cast.ToString(proto.GetExtension(f.Options, proto3.E_MyFileOption)))
dp := protodesc.ToDescriptorProto(m.ProtoReflect().Descriptor())
log.Println(cast.ToInt32(proto.GetExtension(dp.Options, proto3.E_MyMessageOption)))
fdp := protodesc.ToFieldDescriptorProto(m.ProtoReflect().Descriptor().Fields().ByNumber(1))
log.Println(cast.ToFloat64(proto.GetExtension(fdp.Options, proto3.E_MyFieldOption)))
odp := protodesc.ToOneofDescriptorProto(m.ProtoReflect().Descriptor().Oneofs().ByName("qux"))
log.Println(cast.ToInt64(proto.GetExtension(odp.Options, proto3.E_MyOneofOption)))
var e proto3.MyEnum = 123
edp := protodesc.ToEnumDescriptorProto(e.Descriptor())
log.Println(cast.ToBool(proto.GetExtension(edp.Options, proto3.E_MyEnumOption)))
evdp := protodesc.ToEnumValueDescriptorProto(e.Descriptor().Values().ByNumber(0))
log.Println(cast.ToUint32(proto.GetExtension(evdp.Options, proto3.E_MyEnumValueOption)))
sdp := protodesc.ToServiceDescriptorProto(m.ProtoReflect().Descriptor().ParentFile().Services().ByName("MyService"))
i := proto.GetExtension(sdp.Options, proto3.E_MyServiceOption)
log.Println(i.(proto3.MyEnum))
mdp := protodesc.ToMethodDescriptorProto(m.ProtoReflect().Descriptor().ParentFile().Services().ByName("MyService").Methods().ByName("MyMethod"))
i2 := proto.GetExtension(mdp.Options, proto3.E_MyMethodOption)
log.Println(i2.(*proto3.MyMessage).String())
}
func String(v interface{}) string {
b, err := json.Marshal(v)
if err != nil {
panic(err)
}
return string(b)
}
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# Any
Any 允许定义一个可以存储任意类型的字段，底层是 bytes 数组，需要 import google/protobuf/any.proto：
syntax = "proto3";
option go_package = "mytest/proto/proto3";
import "google/protobuf/any.proto";
message A {
string a = 1;
}
message B {
string b = 1;
}
message ErrorStatus {
string message = 1;
repeated google.protobuf.Any details = 2;
}
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Go 示例代码：
func main() {
s := proto3.ErrorStatus{
Message: "test",
}
a := proto3.A{
A: "a",
}
b := proto3.B{
B: "b",
}
anyA, err := anypb.New(&a)
if err != nil {
panic(err)
}
anyB, err := anypb.New(&b)
if err != nil {
panic(err)
}
s.Details = append(s.Details, anyA, anyB)
for _, d := range s.Details {
switch d.MessageName() {
case "A":
pm, err := d.UnmarshalNew()
if err != nil {
panic(err)
}
log.Println(pm.(*proto3.A).String())
case "B":
pm, err := d.UnmarshalNew()
if err != nil {
panic(err)
}
log.Println(pm.(*proto3.B).String())
default:
panic("unknown message name")
}
}
}
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