remove duplicate codes

src/adminserver/api/base.go

@@ -16,6 +16,7 @@
 package api
 
 import (
+	"encoding/json"
 	"net/http"
 )
 
@@ -32,3 +33,17 @@ func handleUnauthorized(w http.ResponseWriter) {
 	http.Error(w, http.StatusText(http.StatusUnauthorized),
 		http.StatusUnauthorized)
 }
+
+// response status code will be written automatically if there is an error
+func writeJSON(w http.ResponseWriter, v interface{}) error {
+	b, err := json.Marshal(v)
+	if err != nil {
+		handleInternalServerError(w)
+		return err
+	}
+
+	if _, err = w.Write(b); err != nil {
+		return err
+	}
+	return nil
+}

src/adminserver/api/cfg.go

@@ -33,14 +33,9 @@ func ListCfgs(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	b, err := json.MarshalIndent(cfg, "", "  ")
+	if err = writeJSON(w, cfg); err != nil {
-	if err != nil {
-		log.Errorf("failed to marshal configurations: %v", err)
-		handleInternalServerError(w)
-		return
-	}
-	if _, err = w.Write(b); err != nil {
 		log.Errorf("failed to write response: %v", err)
+		return
 	}
 }
 

src/adminserver/api/systeminfo.go

@@ -16,7 +16,6 @@
 package api
 
 import (
-	"encoding/json"
 	"net/http"
 
 	"github.com/vmware/harbor/src/adminserver/systeminfo/imagestorage"
@@ -32,14 +31,8 @@ func Capacity(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	b, err := json.Marshal(capacity)
+	if err = writeJSON(w, capacity); err != nil {
-	if err != nil {
+		log.Errorf("failed to write response: %v", err)
-		log.Errorf("failed to marshal capacity: %v", err)
-		handleInternalServerError(w)
 		return
 	}
-
-	if _, err = w.Write(b); err != nil {
-		log.Errorf("failed to write response: %v", err)
-	}
 }

src/adminserver/handlers/handler.go

@@ -24,6 +24,8 @@ import (
 	"github.com/vmware/harbor/src/common/utils/log"
 )
 
+// NewHandler returns a gorilla router which is wrapped by  authenticate handler
+// and logging handler
 func NewHandler() http.Handler {
 	h := newRouter()
 	secrets := map[string]string{