Add EncodeJSONRequest to transport/http

transport/http/client.go

@@ -1,6 +1,9 @@
 package http
 
 import (
+	"bytes"
+	"encoding/json"
+	"io/ioutil"
 	"net/http"
 	"net/url"
 
@@ -113,3 +116,19 @@ func (c Client) Endpoint() endpoint.Endpoint {
 		return response, nil
 	}
 }
+
+// EncodeJSONRequest is an EncodeRequestFunc that serializes the request as a
+// JSON object to the Request body. Many JSON-over-HTTP services can use it as
+// a sensible default. If the request implements Headerer, the provided headers
+// will be applied to the request.
+func EncodeJSONRequest(c context.Context, r *http.Request, request interface{}) error {
+	r.Header.Set("Content-Type", "application/json; charset=utf-8")
+	if headerer, ok := request.(Headerer); ok {
+		for k := range headerer.Headers() {
+			r.Header.Set(k, headerer.Headers().Get(k))
+		}
+	}
+	var b bytes.Buffer
+	r.Body = ioutil.NopCloser(&b)
+	return json.NewEncoder(&b).Encode(request)
+}

transport/http/client_test.go

@@ -2,6 +2,7 @@ package http_test
 
 import (
 	"io"
+	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -140,10 +141,78 @@ func TestHTTPClientBufferedStream(t *testing.T) {
 	}
 }
 
+func TestEncodeJSONRequest(t *testing.T) {
+	var header http.Header
+	var body string
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		b, err := ioutil.ReadAll(r.Body)
+		if err != nil && err != io.EOF {
+			t.Fatal(err)
+		}
+		header = r.Header
+		body = string(b)
+	}))
+
+	defer server.Close()
+
+	serverURL, err := url.Parse(server.URL)
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	client := httptransport.NewClient(
+		"POST",
+		serverURL,
+		httptransport.EncodeJSONRequest,
+		func(context.Context, *http.Response) (interface{}, error) { return nil, nil },
+	).Endpoint()
+
+	for _, test := range []struct {
+		value interface{}
+		body  string
+	}{
+		{nil, "null\n"},
+		{12, "12\n"},
+		{1.2, "1.2\n"},
+		{true, "true\n"},
+		{"test", "\"test\"\n"},
+		{enhancedRequest{Foo: "foo"}, "{\"foo\":\"foo\"}\n"},
+	} {
+		if _, err := client(context.Background(), test.value); err != nil {
+			t.Error(err)
+			continue
+		}
+
+		if body != test.body {
+			t.Errorf("%v: actual %#v, expected %#v", test.value, body, test.body)
+		}
+	}
+
+	if _, err := client(context.Background(), enhancedRequest{Foo: "foo"}); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, ok := header["X-Edward"]; !ok {
+		t.Fatalf("X-Edward value: actual %v, expected %v", nil, []string{"Snowden"})
+	}
+
+	if v := header.Get("X-Edward"); v != "Snowden" {
+		t.Errorf("X-Edward string: actual %v, expected %v", v, "Snowden")
+	}
+}
+
 func mustParse(s string) *url.URL {
 	u, err := url.Parse(s)
 	if err != nil {
 		panic(err)
 	}
 	return u
 }
+
+type enhancedRequest struct {
+	Foo string `json:"foo"`
+}
+
+func (e enhancedRequest) Headers() http.Header { return http.Header{"X-Edward": []string{"Snowden"}} }