You can specify an output directory for the generated Go code:
protoc --go_out=output_dir path/to/yourfile.proto
Replace output_dir with the desired directory path.
You can generate code from multiple .proto files at once:
protoc --go_opt=module=example.com/myapp --go_out=. path/to/yourfile1.proto path/to/yourfile2.proto
This generates Go code for both yourfile1.proto and yourfile2.proto.
You can organize your .proto files into subdirectories and generate code accordingly:
##+BEGIN_SRC shell protoc –go_out=output_dir path/to/proto/*.proto
This processes all .proto files in the specified directory and its subdirectories, generating Go code in the output_dir.
+BEGIN_SRC shell protoc –go_opt=module=example.com/myapp –go_out=. path/to/proto/*.proto
This will process .proto and generate the code in the option go_package specified in .proto file
You can set the Go package name for the generated code:
protoc --go_opt=module=example.com/myapp --go_out=plugins=grpc:. path/to/yourfile.proto
In this example, we use the plugins=grpc option to enable gRPC code generation and set the Go package name.*** Common Command-Line Flags
- `-I` or `–proto_path`: Specifies the directory in which to search for `.proto` files. You can use this flag to specify the import directories.
- `–proto_path=path1,path2`: Allows specifying multiple import directories, separated by commas.
- `–go_out`: Specifies the output directory for Go code generation. For Go, you can use this flag with the `plugins=grpc` option to enable gRPC support.
- `–java_out`: Specifies the output directory for Java code generation.
- `–python_out`: Specifies the output directory for Python code generation.
- `–cpp_out`: Specifies the output directory for C++ code generation.
- `–csharp_out`: Specifies the output directory for C# code generation.
- `–swift_out`: Specifies the output directory for Swift code generation.
The `-I` or `–proto_path` flag is used to specify import directories for `.proto` files. Import directories are essential for resolving imports and including `.proto` files referenced by other files. You can specify one or more directories to search for `.proto` files.
In this example, we specify two import directories (`proto_dir` and `common_proto`) to search for `.proto` files.
In Protocol Buffers (Protobuf), the `go_opt=module=<GoModule>` option is used to specify the Go module name for the generated Go code. This option is particularly useful when you want to ensure that the generated Go code is organized within a specific Go module.
Here’s how you can use this option:
option go_package = "<GoModule>/<GoPackage>";
- `<GoModule>`: Replace this with the name of your Go module where you want the generated code to be placed.
- `<GoPackage>`: Replace this with the desired Go package name within your module.
For example, let’s say you have a Go module named “myapp” and you want the generated Go code to be placed in the “proto” package within that module. You would define it as follows:
option go_package = "myapp/proto";
By specifying the `go_opt=module` option, you ensure that the generated Go code is placed in the appropriate Go module and package, making it easier to manage your Protobuf-generated code within your Go project.
This option is particularly useful when you have multiple Protobuf files and want to organize the generated Go code into a structured project directory. It helps maintain a clear and organized codebase in your Go application.
Protobuf Scalar | Description | Go Type | Python Type | Java Type | Zero Value |
---|---|---|---|---|---|
bool | Boolean value (true or false) | bool | bool | boolean | false |
string | UTF-8 encoded string | string | string | String | ”” (empty) |
bytes | Arbitrary byte sequence (binary data) | []byte | bytes | ByteString | nil |
double | Double-precision floating-point number | float64 | float or double | double | 0.0 |
float | Single-precision floating-point number | float32 | float or double | float | 0.0 |
int32 | 32-bit signed integer | int32 | int | int | 0 |
int64 | 64-bit signed integer | int64 | int | long | 0 |
uint32 | 32-bit unsigned integer | uint32 | int | int | 0 |
uint64 | 64-bit unsigned integer | uint64 | int | long | 0 |
sint32 | Signed 32-bit integer with variable encoding | int32 | int | int | 0 |
sint64 | Signed 64-bit integer with variable encoding | int64 | int | long | 0 |
fixed32 | 32-bit unsigned integer with fixed-width encoding | uint32 | int | int | 0 |
fixed64 | 64-bit unsigned integer with fixed-width encoding | uint64 | int | long | 0 |
sfixed32 | Signed 32-bit integer with fixed-width encoding | int32 | int | int | 0 |
sfixed64 | Signed 64-bit integer with fixed-width encoding | int64 | int | long | 0 |
Optional fields may or may not be present in a message. They are often used for values that might not always be available.
message Person {
string name = 1;
int32 age = 2;
}
In Go, optional fields are represented as pointers:
person := &Person{
name: "Alice",
// You can omit age to make it optional
}
Repeated fields are used for lists or arrays of values and can have zero or more elements. They are ideal for storing multiple instances of a value in a single field.
message ShoppingCart { repeated string items = 1; }
In Go, repeated fields are represented as slices:
cart := &ShoppingCart{
items: []string{"item1", "item2", "item3"},
// You can have an empty slice for zero or more items
}
Default go json encoder doesn’t work with protobuf. Need to import to have encoder.
“google.golang.org/protobuf/encoding/protojson”
2 important function come from protojson
func Marshal(m proto.Message) ([]byte, error)
func Unmarshal(b []byte, m proto.Message) error
package basic
import (
"google.golang.org/protobuf/encoding/protojson"
"grpc-go/protogen/basic"
"log"
)
func ProtoToJsonUser(){
user := &basic.User{
Id: 99,
Username: "Cat women",
IsActive: true,
Password: []byte("654321"),
Emails: []string{"[email protected]"},
Gender: basic.Gender_GENDER_FEMALE,
}
bytesProto, _ := protojson.Marshal(user)
jsonUser := string(bytesProto)
log.Println(jsonUser)
}
- Defining Messages
- Message Fields Overview
- Data Types (int, string, bool, bytes, etc.)
- Field Options and Annotations
- Enumerations in Protobuf
- Oneof Fields (Unions)
- Creating Nested Messages
- Accessing Nested Message Fields
- Extending Protobuf Messages
- Custom Extensions
- Serializing Protobuf Data
- Deserializing Protobuf Data
- Packages and Namespaces
- Custom Options and Extensions
- Compatibility and Versioning
- Protobuf in gRPC (brief introduction)
- Official Protobuf Documentation
- Community and Forums
- Tutorials and Guides