Check for Null Parameters in the Feature APIs (#161)

* check for null parameters in feature APIs
* add null parameter tests for isFeatureEnabled
* add null parameter tests for getFeatureVariableBoolean
* add null parameter tests for getFeatureVariableDouble
* add null parameter tests for getFeatureVariableInteger
* add null parameter tests for getFeatureVariableString

Author: wangjoshuah

core-api/src/main/java/com/optimizely/ab/Optimizely.java

@@ -1,5 +1,5 @@
 /****************************************************************************
- * Copyright 2016-2017, Optimizely, Inc. and contributors                   *
+ * Copyright 2016-2018, Optimizely, Inc. and contributors                   *
  *                                                                          *
  * Licensed under the Apache License, Version 2.0 (the "License");          *
  * you may not use this file except in compliance with the License.         *
@@ -43,21 +43,19 @@
 import com.optimizely.ab.notification.NotificationBroadcaster;
 import com.optimizely.ab.notification.NotificationCenter;
 import com.optimizely.ab.notification.NotificationListener;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import javax.annotation.CheckForNull;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.ThreadSafe;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
-import javax.annotation.CheckForNull;
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.ThreadSafe;
-
 /**
  * Top-level container class for Optimizely functionality.
  * Thread-safe, so can be created as a singleton and safely passed around.
@@ -333,6 +331,14 @@ public void track(@Nonnull String eventName,
     public @Nonnull Boolean isFeatureEnabled(@Nonnull String featureKey,
                                               @Nonnull String userId,
                                               @Nonnull Map<String, String> attributes) {
+        if (featureKey == null) {
+            logger.warn("The featureKey parameter must be nonnull.");
+            return false;
+        }
+        else if (userId == null) {
+            logger.warn("The userId parameter must be nonnull.");
+            return false;
+        }
         FeatureFlag featureFlag = projectConfig.getFeatureKeyMapping().get(featureKey);
         if (featureFlag == null) {
             logger.info("No feature flag was found for key \"{}\".", featureKey);
@@ -533,6 +539,18 @@ String getFeatureVariableValueForType(@Nonnull String featureKey,
                                                   @Nonnull String userId,
                                                   @Nonnull Map<String, String> attributes,
                                                   @Nonnull LiveVariable.VariableType variableType) {
+        if (featureKey == null) {
+            logger.warn("The featureKey parameter must be nonnull.");
+            return null;
+        }
+        else if (variableKey == null) {
+            logger.warn("The variableKey parameter must be nonnull.");
+            return null;
+        }
+        else if (userId == null) {
+            logger.warn("The userId parameter must be nonnull.");
+            return null;
+        }
         FeatureFlag featureFlag = projectConfig.getFeatureKeyMapping().get(featureKey);
         if (featureFlag == null) {
             logger.info("No feature flag was found for key \"{}\".", featureKey);