add protojson (#952)

encoding/json/json.go

@@ -5,11 +5,24 @@ import (
 	"reflect"
 
 	"github.com/go-kratos/kratos/v2/encoding"
+	"google.golang.org/protobuf/encoding/protojson"
+	"google.golang.org/protobuf/proto"
 )
 
 // Name is the name registered for the json codec.
 const Name = "json"
 
+var (
+	// MarshalOptions is a configurable JSON format marshaler.
+	MarshalOptions = protojson.MarshalOptions{
+		EmitUnpopulated: true,
+	}
+	// UnmarshalOptions is a configurable JSON format parser.
+	UnmarshalOptions = protojson.UnmarshalOptions{
+		DiscardUnknown: true,
+	}
+)
+
 func init() {
 	encoding.RegisterCodec(codec{})
 }
@@ -18,6 +31,9 @@ func init() {
 type codec struct{}
 
 func (codec) Marshal(v interface{}) ([]byte, error) {
+	if m, ok := v.(proto.Message); ok {
+		return MarshalOptions.Marshal(m)
+	}
 	return json.Marshal(v)
 }
 
@@ -29,6 +45,11 @@ func (codec) Unmarshal(data []byte, v interface{}) error {
 		}
 		rv = rv.Elem()
 	}
+	if m, ok := v.(proto.Message); ok {
+		return UnmarshalOptions.Unmarshal(data, m)
+	} else if m, ok := reflect.Indirect(reflect.ValueOf(v)).Interface().(proto.Message); ok {
+		return UnmarshalOptions.Unmarshal(data, m)
+	}
 	return json.Unmarshal(data, v)
 }
 

examples/proto/echo_service_test.go

@@ -134,6 +134,7 @@ func testEchoClient(t *testing.T, addr string) {
 	if din.Body.ValueField.GetStringValue() != dout.Body.ValueField.GetStringValue() {
 		t.Fatalf("EchoPatch expected %s got %s", din, dout)
 	}
+	fmt.Println("echo test success!")
 }
 
 func TestJSON(t *testing.T) {