Generalize the logic to disallow nested objects and arrays as keys in objects.

Fixes #771.

src/main/java/org/json/JSONObject.java

@@ -208,22 +208,14 @@ public class JSONObject {
             throw x.syntaxError("A JSONObject text must begin with '{'");
         }
         for (;;) {
-            char prev = x.getPrevious();
             c = x.nextClean();
             switch (c) {
             case 0:
                 throw x.syntaxError("A JSONObject text must end with '}'");
             case '}':
                 return;
-            case '{':
-            case '[':
-                if(prev=='{') {
-                    throw x.syntaxError("A JSON Object can not directly nest another JSON Object or JSON Array.");
-                }
-                // fall through
             default:
-                x.back();
-                key = x.nextValue().toString();
+                key = x.nextSimpleValue(c).toString();
             }
 
             // The key is followed by ':'.

src/main/java/org/json/JSONTokener.java

@@ -402,12 +402,7 @@ public class JSONTokener {
      */
     public Object nextValue() throws JSONException {
         char c = this.nextClean();
-        String string;
-
         switch (c) {
-        case '"':
-        case '\'':
-            return this.nextString(c);
         case '{':
             this.back();
             try {
@@ -423,6 +418,21 @@ public class JSONTokener {
                 throw new JSONException("JSON Array or Object depth too large to process.", e);
             }
         }
+        return nextSimpleValue(c);
+    }
+
+    Object nextSimpleValue(char c) {
+        String string;
+
+        switch (c) {
+        case '"':
+        case '\'':
+            return this.nextString(c);
+        case '{':
+            throw syntaxError("Nested object not expected here.");
+        case '[':
+            throw syntaxError("Nested array not expected here.");
+        }
 
         /*
          * Handle unquoted text. This could be the values true, false, or

src/test/java/org/json/junit/JSONObjectTest.java

@@ -2224,6 +2224,24 @@ public class JSONObjectTest {
                     "Expected a ',' or '}' at 15 [character 16 line 1]",
                     e.getMessage());
         }
+        try {
+            // key is a nested map
+            String str = "{{\"foo\": \"bar\"}: \"baz\"}";
+            assertNull("Expected an exception",new JSONObject(str));
+        } catch (JSONException e) {
+            assertEquals("Expecting an exception message",
+                "Nested object not expected here. at 2 [character 3 line 1]",
+                e.getMessage());
+        }
+        try {
+            // key is a nested array containing a map
+            String str = "{\"a\": 1, [{\"foo\": \"bar\"}]: \"baz\"}";
+            assertNull("Expected an exception",new JSONObject(str));
+        } catch (JSONException e) {
+            assertEquals("Expecting an exception message",
+                "Nested array not expected here. at 10 [character 11 line 1]",
+                e.getMessage());
+        }
         try {
             // \0 after ,
             String str = "{\"myKey\":true, \0\"myOtherKey\":false}";