checking empty string in examples for #2783

Author: lucasoares

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

@@ -404,7 +404,7 @@ public void setAllowEmptyValue(Boolean allowEmptyValue) {
 
     @JsonProperty("x-example")
     public Object getExample() {
-        if (example == null) {
+        if (example == null || example.isEmpty()) {
             return null;
         }
         try {

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

@@ -4,6 +4,7 @@
 import io.swagger.models.properties.BaseIntegerProperty;
 import io.swagger.models.properties.BooleanProperty;
 import io.swagger.models.properties.DecimalProperty;
+import io.swagger.models.properties.LongProperty;
 import io.swagger.models.properties.Property;
 import io.swagger.models.properties.StringProperty;
 import org.testng.annotations.BeforeMethod;
@@ -335,6 +336,19 @@ public void testGetExampleWithDecimalProperty() {
                 "The example value must not change when when set an array property");
     }
 
+    @Test
+    public void testGetExampleWithEmptyString() {
+        // given
+        instance.setProperty(new LongProperty());
+        example = "";
+
+        // when
+        instance.setExample(example);
+
+        // then
+        assertEquals(instance.getExample(), null, "The example must be null if the value is an empty string");
+    }
+
     @Test
     public void testGetExampleWithBooleanProperty() {
         // given