Added validator and replaced use of booleans with enum
diff --git a/src/main/java/org/apache/geode/kafka/GeodeConnectorConfig.java b/src/main/java/org/apache/geode/kafka/GeodeConnectorConfig.java
index 8043dbb..e5590c7 100644
--- a/src/main/java/org/apache/geode/kafka/GeodeConnectorConfig.java
+++ b/src/main/java/org/apache/geode/kafka/GeodeConnectorConfig.java
@@ -86,6 +86,7 @@
         TASK_ID,
         ConfigDef.Type.INT,
         "0",
+        ConfigDef.Range.atLeast(0),
         ConfigDef.Importance.MEDIUM,
         TASK_ID_DOCUMENTATION,
         GEODE_GROUP,
diff --git a/src/main/java/org/apache/geode/kafka/sink/GeodeKafkaSinkTask.java b/src/main/java/org/apache/geode/kafka/sink/GeodeKafkaSinkTask.java
index a568616..c0fde75 100644
--- a/src/main/java/org/apache/geode/kafka/sink/GeodeKafkaSinkTask.java
+++ b/src/main/java/org/apache/geode/kafka/sink/GeodeKafkaSinkTask.java
@@ -74,7 +74,7 @@
   void configure(GeodeSinkConnectorConfig geodeConnectorConfig) {
     logger.debug("GeodeKafkaSourceTask id:" + geodeConnectorConfig.getTaskId() + " starting");
     topicToRegions = geodeConnectorConfig.getTopicToRegions();
-    nullValuesMeansRemove = geodeConnectorConfig.getNullValuesMeanRemove();
+    nullValuesMeansRemove = geodeConnectorConfig.getNullValueBehavior();
   }
 
   // For tests only
diff --git a/src/main/java/org/apache/geode/kafka/sink/GeodeSinkConnectorConfig.java b/src/main/java/org/apache/geode/kafka/sink/GeodeSinkConnectorConfig.java
index 643b740..968004f 100644
--- a/src/main/java/org/apache/geode/kafka/sink/GeodeSinkConnectorConfig.java
+++ b/src/main/java/org/apache/geode/kafka/sink/GeodeSinkConnectorConfig.java
@@ -14,11 +14,11 @@
  */
 package org.apache.geode.kafka.sink;
 
-import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.DEFAULT_NULL_VALUES_MEAN_REMOVE;
+import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.DEFAULT_NULL_VALUES_BEHAVIOR;
 import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.DEFAULT_TOPIC_TO_REGION_BINDING;
-import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.NULL_VALUES_MEAN_REMOVE;
-import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.NULL_VALUES_MEAN_REMOVE_DISPLAY_NAME;
-import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.NULL_VALUES_MEAN_REMOVE_DOCUMENTATION;
+import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.NULL_VALUES_BEHAVIOR;
+import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.NULL_VALUES_BEHAVIOR_DISPLAY_NAME;
+import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.NULL_VALUES_BEHAVIOR_DOCUMENTATION;
 import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.SINK_GROUP;
 import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.TOPIC_TO_REGION_BINDINGS;
 import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.TOPIC_TO_REGION_BINDINGS_DISPLAY_NAME;
@@ -30,16 +30,19 @@
 import org.apache.kafka.common.config.ConfigDef;
 
 import org.apache.geode.kafka.GeodeConnectorConfig;
+import org.apache.geode.kafka.utils.EnumValidator;
+import org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants;
 
 public class GeodeSinkConnectorConfig extends GeodeConnectorConfig {
   public static final ConfigDef SINK_CONFIG_DEF = configurables();
   private final Map<String, List<String>> topicToRegions;
-  private final boolean nullValuesMeanRemove;
+  private final GeodeSinkConfigurationConstants.NullValueBehavior nullValueBehavior;
 
   public GeodeSinkConnectorConfig(Map<String, String> connectorProperties) {
     super(SINK_CONFIG_DEF, connectorProperties);
     topicToRegions = parseTopicToRegions(getString(TOPIC_TO_REGION_BINDINGS));
-    nullValuesMeanRemove = getBoolean(NULL_VALUES_MEAN_REMOVE);
+    nullValueBehavior = GeodeSinkConfigurationConstants.NullValueBehavior
+        .valueOf(getString(NULL_VALUES_BEHAVIOR).toUpperCase());
   }
 
   protected static ConfigDef configurables() {
@@ -56,15 +59,16 @@
         TOPIC_TO_REGION_BINDINGS_DISPLAY_NAME);
 
     configDef.define(
-        NULL_VALUES_MEAN_REMOVE,
-        ConfigDef.Type.BOOLEAN,
-        DEFAULT_NULL_VALUES_MEAN_REMOVE,
+        NULL_VALUES_BEHAVIOR,
+        ConfigDef.Type.STRING,
+        DEFAULT_NULL_VALUES_BEHAVIOR,
+        EnumValidator.in(GeodeSinkConfigurationConstants.NullValueBehavior.values()),
         ConfigDef.Importance.MEDIUM,
-        NULL_VALUES_MEAN_REMOVE_DOCUMENTATION,
+        NULL_VALUES_BEHAVIOR_DOCUMENTATION,
         SINK_GROUP,
         2,
         ConfigDef.Width.MEDIUM,
-        NULL_VALUES_MEAN_REMOVE_DISPLAY_NAME);
+        NULL_VALUES_BEHAVIOR_DISPLAY_NAME);
     return configDef;
   }
 
@@ -72,8 +76,12 @@
     return topicToRegions;
   }
 
-  public boolean getNullValuesMeanRemove() {
-    return nullValuesMeanRemove;
+  public boolean getNullValueBehavior() {
+    if (nullValueBehavior.equals(GeodeSinkConfigurationConstants.NullValueBehavior.REMOVE)) {
+      return true;
+    } else {
+      return false;
+    }
   }
 
 }
diff --git a/src/main/java/org/apache/geode/kafka/utils/EnumValidator.java b/src/main/java/org/apache/geode/kafka/utils/EnumValidator.java
new file mode 100644
index 0000000..1c9e1ff
--- /dev/null
+++ b/src/main/java/org/apache/geode/kafka/utils/EnumValidator.java
@@ -0,0 +1,45 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
+ * agreements. See the NOTICE file distributed with this work for additional information regarding
+ * copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License. You may obtain a
+ * copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package org.apache.geode.kafka.utils;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.apache.kafka.common.config.ConfigDef;
+import org.apache.kafka.common.config.ConfigException;
+
+public class EnumValidator implements ConfigDef.Validator {
+  private final Set<String> validValues;
+
+  public EnumValidator(Set<String> validValues) {
+    this.validValues = validValues;
+  }
+
+  public static <T> EnumValidator in(T[] enumerators) {
+    Set<String> validValues = new HashSet<String>(enumerators.length);
+    for (T e : enumerators) {
+      validValues.add(e.toString().toLowerCase());
+    }
+    return new EnumValidator(validValues);
+  }
+
+  @Override
+  public void ensureValid(String key, Object value) {
+    if (!validValues.contains(value.toString().toLowerCase())) {
+      throw new ConfigException(key, value, "Invalid enumeration value");
+    }
+
+  }
+}
diff --git a/src/main/java/org/apache/geode/kafka/utils/GeodeSinkConfigurationConstants.java b/src/main/java/org/apache/geode/kafka/utils/GeodeSinkConfigurationConstants.java
index 1c550b5..982057b 100644
--- a/src/main/java/org/apache/geode/kafka/utils/GeodeSinkConfigurationConstants.java
+++ b/src/main/java/org/apache/geode/kafka/utils/GeodeSinkConfigurationConstants.java
@@ -20,14 +20,18 @@
    */
   public static final String TOPIC_TO_REGION_BINDINGS = "topic-to-regions";
   public static final String DEFAULT_TOPIC_TO_REGION_BINDING = "[gkcTopic:gkcRegion]";
-  public static final String NULL_VALUES_MEAN_REMOVE = "null-values-mean-remove";
-  public static final String DEFAULT_NULL_VALUES_MEAN_REMOVE = "true";
-  public static final String NULL_VALUES_MEAN_REMOVE_DOCUMENTATION =
-      "If set to true, when topics send a SinkRecord with a null value, we will convert to an operation similar to region.remove instead of putting a null value into the region";
+  public static final String NULL_VALUES_BEHAVIOR = "null-values-behavior";
+  public static final String DEFAULT_NULL_VALUES_BEHAVIOR = "remove";
+  public static final String NULL_VALUES_BEHAVIOR_DOCUMENTATION =
+      "If set to REMOVE, when topics send a SinkRecord with a null value, we will convert to an operation similar to region.remove instead of putting a null value into the region";
   public static final String TOPIC_TO_REGION_BINDINGS_DOCUMENTATION =
       "A comma separated list of \"one topic to many regions\" bindings.  Each binding is surrounded by brackets. For example \"[topicName:regionName], [anotherTopic: regionName, anotherRegion]";
   public static final String SINK_GROUP = "Sink-Configurations";
   public final static String TOPIC_TO_REGION_BINDINGS_DISPLAY_NAME = "Topic to region mapping";
-  public final static String NULL_VALUES_MEAN_REMOVE_DISPLAY_NAME = "Null values behavior";
+  public final static String NULL_VALUES_BEHAVIOR_DISPLAY_NAME = "Null values behavior";
 
+  public enum NullValueBehavior {
+    REMOVE,
+    ADD
+  }
 }
diff --git a/src/test/java/org/apache/geode/kafka/sink/GeodeKafkaSinkTaskTest.java b/src/test/java/org/apache/geode/kafka/sink/GeodeKafkaSinkTaskTest.java
index c5e5056..7b987d9 100644
--- a/src/test/java/org/apache/geode/kafka/sink/GeodeKafkaSinkTaskTest.java
+++ b/src/test/java/org/apache/geode/kafka/sink/GeodeKafkaSinkTaskTest.java
@@ -16,7 +16,7 @@
 
 import static org.apache.geode.kafka.utils.GeodeConfigurationConstants.LOCATORS;
 import static org.apache.geode.kafka.utils.GeodeConfigurationConstants.TASK_ID;
-import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.NULL_VALUES_MEAN_REMOVE;
+import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.NULL_VALUES_BEHAVIOR;
 import static org.apache.geode.kafka.utils.GeodeSinkConfigurationConstants.TOPIC_TO_REGION_BINDINGS;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
@@ -40,7 +40,7 @@
     HashMap<String, String> props = new HashMap<>();
     props.put(TOPIC_TO_REGION_BINDINGS, "[topic:region]");
     props.put(TASK_ID, "0");
-    props.put(NULL_VALUES_MEAN_REMOVE, "true");
+    props.put(NULL_VALUES_BEHAVIOR, "REMOVE");
     props.put(LOCATORS, "localhost[10334]");
     return props;
   }