add json ASCII string render (#1358)

add a json render that rendering json as ASCII string

render/json.go

@@ -6,6 +6,7 @@ package render
 
 import (
 	"bytes"
+	"fmt"
 	"html/template"
 	"net/http"
 
@@ -30,10 +31,15 @@ type JsonpJSON struct {
 	Data     interface{}
 }
 
+type AsciiJSON struct {
+	Data interface{}
+}
+
 type SecureJSONPrefix string
 
 var jsonContentType = []string{"application/json; charset=utf-8"}
 var jsonpContentType = []string{"application/javascript; charset=utf-8"}
+var jsonAsciiContentType = []string{"application/json"}
 
 func (r JSON) Render(w http.ResponseWriter) (err error) {
 	if err = WriteJSON(w, r.Data); err != nil {
@@ -112,3 +118,29 @@ func (r JsonpJSON) Render(w http.ResponseWriter) (err error) {
 func (r JsonpJSON) WriteContentType(w http.ResponseWriter) {
 	writeContentType(w, jsonpContentType)
 }
+
+func (r AsciiJSON) Render(w http.ResponseWriter) (err error) {
+	r.WriteContentType(w)
+	ret, err := json.Marshal(r.Data)
+	if err != nil {
+		return err
+	}
+
+	var buffer bytes.Buffer
+	for _, r := range string(ret) {
+		cvt := ""
+		if r < 128 {
+			cvt = string(r)
+		} else {
+			cvt = fmt.Sprintf("\\u%04x", int64(r))
+		}
+		buffer.WriteString(cvt)
+	}
+
+	w.Write(buffer.Bytes())
+	return nil
+}
+
+func (r AsciiJSON) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, jsonAsciiContentType)
+}

render/render_test.go

@@ -167,6 +167,35 @@ func TestRenderJsonpJSONFail(t *testing.T) {
 	assert.Error(t, err)
 }
 
+func TestRenderAsciiJSON(t *testing.T) {
+	w1 := httptest.NewRecorder()
+	data1 := map[string]interface{}{
+		"lang": "GO语言",
+		"tag":  "<br>",
+	}
+
+	err := (AsciiJSON{data1}).Render(w1)
+
+	assert.NoError(t, err)
+	assert.Equal(t, "{\"lang\":\"GO\\u8bed\\u8a00\",\"tag\":\"\\u003cbr\\u003e\"}", w1.Body.String())
+	assert.Equal(t, "application/json", w1.Header().Get("Content-Type"))
+
+	w2 := httptest.NewRecorder()
+	data2 := float64(3.1415926)
+
+	err = (AsciiJSON{data2}).Render(w2)
+	assert.NoError(t, err)
+	assert.Equal(t, "3.1415926", w2.Body.String())
+}
+
+func TestRenderAsciiJSONFail(t *testing.T) {
+	w := httptest.NewRecorder()
+	data := make(chan int)
+
+	// json: unsupported type: chan int
+	assert.Error(t, (AsciiJSON{data}).Render(w))
+}
+
 type xmlmap map[string]interface{}
 
 // Allows type H to be used with xml.Marshal