refs #2783 - avoid NumberFormatException warning with empty String in param example

Author: frantuma

modules/swagger-models/src/main/java/io/swagger/models/parameters/AbstractSerializableParameter.java

@@ -405,7 +405,7 @@ public void setAllowEmptyValue(Boolean allowEmptyValue) {
     @JsonProperty("x-example")
     public Object getExample() {
         if (example == null || example.isEmpty()) {
-            return null;
+            return example;
         }
         try {
             if (BaseIntegerProperty.TYPE.equals(type)) {

modules/swagger-models/src/test/java/io/swagger/models/parameters/AbstractSerializableParameterTest.java

@@ -340,13 +340,20 @@ public void testGetExampleWithDecimalProperty() {
     public void testGetExampleWithEmptyString() {
         // given
         instance.setProperty(new LongProperty());
-        example = "";
+        example = null;
 
         // when
         instance.setExample(example);
 
         // then
-        assertEquals(instance.getExample(), null, "The example must be null if the value is an empty string");
+        assertEquals(instance.getExample(), null, "The example must be null if the value is null");
+
+        // given
+        instance.setProperty(new LongProperty());
+        example = "";
+        
+        // then
+        assertEquals(instance.getExample(), null, "The example must be empty string if the value is an empty string");
     }
 
     @Test