add form encoding (#1138)

* add form encoding

* update examples go mod

encoding/form/form.go

@@ -0,0 +1,45 @@
+package form
+
+import (
+	"github.com/go-kratos/kratos/v2/encoding"
+	"github.com/gorilla/schema"
+	"net/url"
+)
+
+const Name = "x-www-form-urlencoded"
+
+func init() {
+	decoder := schema.NewDecoder()
+	decoder.SetAliasTag("json")
+	encoder := schema.NewEncoder()
+	encoder.SetAliasTag("json")
+	encoding.RegisterCodec(codec{encoder: encoder, decoder: decoder})
+}
+
+type codec struct {
+	encoder *schema.Encoder
+	decoder *schema.Decoder
+}
+
+func (c codec) Marshal(v interface{}) ([]byte, error) {
+	var vs = url.Values{}
+	if err := c.encoder.Encode(v, vs); err != nil {
+		return nil, err
+	}
+	return []byte(vs.Encode()), nil
+}
+
+func (c codec) Unmarshal(data []byte, v interface{}) error {
+	vs, err := url.ParseQuery(string(data))
+	if err != nil {
+		return err
+	}
+	if err := c.decoder.Decode(v, vs); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (codec) Name() string {
+	return Name
+}

encoding/form/form_test.go

@@ -0,0 +1,47 @@
+package form
+
+import (
+	"github.com/go-kratos/kratos/v2/encoding"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+type LoginRequest struct {
+	Username string `json:"username,omitempty"`
+	Password string `json:"password,omitempty"`
+}
+
+const contentType = "x-www-form-urlencoded"
+
+func TestFormCodecMarshal(t *testing.T) {
+	req := &LoginRequest{
+		Username: "kratos",
+		Password: "kratos_pwd",
+	}
+	content, err := encoding.GetCodec(contentType).Marshal(req)
+	require.NoError(t, err)
+	require.Equal(t, []byte("password=kratos_pwd&username=kratos"), content)
+
+	req = &LoginRequest{
+		Username: "kratos",
+		Password: "",
+	}
+	content, err = encoding.GetCodec(contentType).Marshal(req)
+	require.NoError(t, err)
+	require.Equal(t, []byte("username=kratos"), content)
+}
+
+func TestFormCodecUnmarshal(t *testing.T) {
+	req := &LoginRequest{
+		Username: "kratos",
+		Password: "kratos_pwd",
+	}
+	content, err := encoding.GetCodec(contentType).Marshal(req)
+	require.NoError(t, err)
+
+	var bindReq = new(LoginRequest)
+	err = encoding.GetCodec(contentType).Unmarshal(content, bindReq)
+	require.NoError(t, err)
+	require.Equal(t, "kratos", bindReq.Username)
+	require.Equal(t, "kratos_pwd", bindReq.Password)
+}