Refactor criterion codec

The previous implementation was a huge switch statement. These
changes attempt to use polymorphism to avoid all of the branching
inherent in a switch.

Change-Id: If997f028346de02b883356bcde07f62674e319be

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed 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.onosproject.codec.impl;
+
+import java.util.EnumMap;
+
+import org.junit.Test;
+import org.onosproject.net.flow.criteria.Criterion;
+
+import static org.onlab.junit.TestUtils.getField;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.*;
+
+/**
+ * Unit tests for criterion codec.
+ */
+public class CriterionCodecTest {
+
+    /**
+     * Checks that all criterion types are covered by the codec.
+     */
+    @Test
+    public void checkCriterionTypes() throws Exception {
+        CriterionCodec codec = new CriterionCodec();
+        EnumMap<Criterion.Type, Object> formatMap = getField(codec, "formatMap");
+        assertThat(formatMap, notNullValue());
+
+        for (Criterion.Type type : Criterion.Type.values()) {
+            assertThat("Entry not found for " + type.toString(),
+                    formatMap.get(type), notNullValue());
+        }
+    }
+}