add a method to set the indentJsonIndentString used in Context.IndentedJSON

context.go

@@ -859,7 +859,7 @@ func (c *Context) HTML(code int, name string, obj interface{}) {
 // WARNING: we recommend to use this only for development purposes since printing pretty JSON is
 // more CPU and bandwidth consuming. Use Context.JSON() instead.
 func (c *Context) IndentedJSON(code int, obj interface{}) {
-	c.Render(code, render.IndentedJSON{Data: obj})
+	c.Render(code, render.IndentedJSON{IndentString: c.engine.indentJsonIndentString, Data: obj})
 }
 
 // SecureJSON serializes the given struct as Secure JSON into the response body.

gin.go

@@ -11,6 +11,7 @@ import (
 	"net/http"
 	"os"
 	"path"
+	"strings"
 	"sync"
 
 	"github.com/gin-gonic/gin/internal/bytesconv"
@@ -19,6 +20,9 @@ import (
 
 const defaultMultipartMemory = 32 << 20 // 32 MB
 
+// A space string
+var spaceString = string(32)
+
 var (
 	default404Body   = []byte("404 page not found")
 	default405Body   = []byte("405 method not allowed")
@@ -112,6 +116,7 @@ type Engine struct {
 	noMethod               HandlersChain
 	pool                   sync.Pool
 	trees                  methodTrees
+	indentJsonIndentString string
 }
 
 var _ IRouter = &Engine{}
@@ -145,6 +150,7 @@ func New() *Engine {
 		trees:                  make(methodTrees, 0, 9),
 		delims:                 render.Delims{Left: "{{", Right: "}}"},
 		secureJsonPrefix:       "while(1);",
+		indentJsonIndentString: strings.Repeat(spaceString, 4),
 	}
 	engine.RouterGroup.engine = engine
 	engine.pool.New = func() interface{} {
@@ -177,6 +183,13 @@ func (engine *Engine) SecureJsonPrefix(prefix string) *Engine {
 	return engine
 }
 
+// IndentJsonIndentSpaceNum sets the indentJsonIndentString used in Context.IndentedJSON.
+// When we use Context.IndentedJSON, we can use custom indentation to render the response.
+func (engine *Engine) IndentJsonIndentSpaceNum(spaceNum int) *Engine {
+	engine.indentJsonIndentString = strings.Repeat(spaceString, spaceNum)
+	return engine
+}
+
 // LoadHTMLGlob loads HTML files identified by glob pattern
 // and associates the result with HTML renderer.
 func (engine *Engine) LoadHTMLGlob(pattern string) {

gin_test.go

@@ -6,13 +6,16 @@ package gin
 
 import (
 	"crypto/tls"
+	"encoding/json"
 	"fmt"
 	"html/template"
 	"io/ioutil"
+	"math/rand"
 	"net/http"
 	"net/http/httptest"
 	"reflect"
 	"strconv"
+	"strings"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -544,3 +547,35 @@ func assertRoutePresent(t *testing.T, gotRoutes RoutesInfo, wantRoute RouteInfo)
 
 func handlerTest1(c *Context) {}
 func handlerTest2(c *Context) {}
+
+// Engine.IndentJsonIndentSpaceNum
+func TestEngine_IndentJsonIndentSpaceNum(t *testing.T) {
+
+	rand.Seed(time.Now().UnixNano())
+	spaceNum := rand.Intn(10)
+
+	router := Default()
+	defaultResponse := H{"name": "test", "age": 20}
+	router.IndentJsonIndentSpaceNum(spaceNum)
+	router.GET("/test", func(c *Context) {
+		c.IndentedJSON(200, defaultResponse)
+	})
+	s := httptest.NewServer(router)
+	defer s.Close()
+
+	req, err := http.NewRequest("GET", "/test", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rr := httptest.NewRecorder()
+	router.ServeHTTP(rr, req)
+	if rr.Code != http.StatusOK {
+		t.Fatal("error code: ", rr.Code)
+	}
+
+	except, _ := json.MarshalIndent(defaultResponse, "", strings.Repeat(spaceString, spaceNum))
+
+	assert.Equal(t, rr.Body.Bytes(), except)
+	t.Log(rr.Body.String())
+}

render/json.go

@@ -21,6 +21,7 @@ type JSON struct {
 
 // IndentedJSON contains the given interface object.
 type IndentedJSON struct {
+	IndentString string
 	Data interface{}
 }
 
@@ -80,7 +81,7 @@ func WriteJSON(w http.ResponseWriter, obj interface{}) error {
 // Render (IndentedJSON) marshals the given interface object and writes it with custom ContentType.
 func (r IndentedJSON) Render(w http.ResponseWriter) error {
 	r.WriteContentType(w)
-	jsonBytes, err := json.MarshalIndent(r.Data, "", "    ")
+	jsonBytes, err := json.MarshalIndent(r.Data, "", r.IndentString)
 	if err != nil {
 		return err
 	}

render/render_test.go

@@ -55,7 +55,7 @@ func TestRenderIndentedJSON(t *testing.T) {
 		"bar": "foo",
 	}
 
-	err := (IndentedJSON{data}).Render(w)
+	err := (IndentedJSON{"    ", data}).Render(w)
 
 	assert.NoError(t, err)
 	assert.Equal(t, "{\n    \"bar\": \"foo\",\n    \"foo\": \"bar\"\n}", w.Body.String())
@@ -67,7 +67,7 @@ func TestRenderIndentedJSONPanics(t *testing.T) {
 	data := make(chan int)
 
 	// json: unsupported type: chan int
-	err := (IndentedJSON{data}).Render(w)
+	err := (IndentedJSON{"", data}).Render(w)
 	assert.Error(t, err)
 }