Fix Issue #497 and add a testcase (#699)

* The method getPropertyKeys() in class JsonOrgJsonProvider doesn't check empty jsonObject.

* Addition testcase

* simplify the implementation. And change method names of testcases to something more descriptive

* change names

json-path/src/main/java/com/jayway/jsonpath/spi/json/JsonOrgJsonProvider.java

@@ -14,6 +14,7 @@ import java.io.UnsupportedEncodingException;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Objects;
 
 public class JsonOrgJsonProvider extends AbstractJsonProvider {
 
@@ -143,17 +144,14 @@ public class JsonOrgJsonProvider extends AbstractJsonProvider {
         return (obj instanceof JSONObject);
     }
 
+    @SuppressWarnings("unchecked")
     @Override
     public Collection<String> getPropertyKeys(Object obj) {
         JSONObject jsonObject = toJsonObject(obj);
-        List<String> keys = new ArrayList<String>();
         try {
-            for (int i = 0; i < jsonObject.names().length(); i++) {
-                String key = (String) jsonObject.names().get(i);
-                keys.add(key);
-
-            }
-            return keys;
+            if(Objects.isNull(jsonObject.names()))
+                return new ArrayList<>();
+            return jsonObject.keySet();
         } catch (JSONException e) {
             throw new JsonPathException(e);
         }

json-path/src/test/java/com/jayway/jsonpath/JsonOrgJsonProviderTest.java

@@ -1,5 +1,7 @@
 package com.jayway.jsonpath;
 
+import com.jayway.jsonpath.spi.json.JsonOrgJsonProvider;
+import com.jayway.jsonpath.spi.mapper.JsonOrgMappingProvider;
 import org.json.JSONArray;
 import org.json.JSONObject;
 import org.junit.Test;
@@ -76,4 +78,23 @@ public class JsonOrgJsonProviderTest extends BaseTest {
         assertThat(result).isEqualTo(4);
     }
 
+    @Test
+    public void test_getPropertyKeys_empty_object() {
+        String json = "{\"foo\": \"bar\", \"emptyObject\": {},\"emptyList\":[]}";
+        Configuration config = Configuration.defaultConfiguration()
+                .jsonProvider(new JsonOrgJsonProvider())
+                .mappingProvider(new JsonOrgMappingProvider());
+        Object result = JsonPath.using(config).parse(json).read("$..foo");
+        assertThat(result.toString()).isEqualTo("[\"bar\"]");
+    }
+
+    @Test
+    public void test_getPropertyKeys_empty_nest_object() {
+        String json = "{\"foo\": \"bar\", \"emptyObject\": {\"emptyList\":[]},\"emptyList\":[]}";
+        Configuration config = Configuration.defaultConfiguration()
+                .jsonProvider(new JsonOrgJsonProvider())
+                .mappingProvider(new JsonOrgMappingProvider());
+        Object result = JsonPath.using(config).parse(json).read("$..foo");
+        assertThat(result.toString()).isEqualTo("[\"bar\"]");
+    }
 }