Configure Jackson ObjectMapper once

This changes the initialization on demand holder for
ObjectMapper to configure the mapper once. Previously
the mapper was being created once but reconfigured on
each access.

Fix for #76

Author: dehora

intercom-java/src/main/java/io/intercom/api/MapperSupport.java

@@ -9,34 +9,32 @@
 public class MapperSupport {
 
     public static ObjectMapper objectMapper() {
-        final ObjectMapper om = Holder.INSTANCE;
-        configure(om);
-        return om;
+        return Holder.INSTANCE;
     }
 
-    private static void configure(ObjectMapper objectMapper) {
-        objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, true);
-        objectMapper.configure(SerializationFeature.INDENT_OUTPUT, true);
-        objectMapper.configure(SerializationFeature.WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS, false);
-        objectMapper.configure(DeserializationFeature.READ_DATE_TIMESTAMPS_AS_NANOSECONDS, false);
-        objectMapper.registerModule(customAttributeModule());
-    }
+    private static class Holder {
+        private static final ObjectMapper INSTANCE = new Holder().configure(new ObjectMapper());
 
-    private static SimpleModule customAttributeModule() {
-        final SimpleModule customAttributeModule = new SimpleModule(
-            "IntercomClientModule",
-            new Version(1, 0, 0, null, "", "")
-        );
-        customAttributeModule.addDeserializer(CustomAttribute.class, new CustomAttributeDeserializer());
-        customAttributeModule.addSerializer(CustomAttribute.class, new CustomAttributeSerializer());
-        customAttributeModule.addDeserializer(Subscription.Topic.class, new TopicDeserializer());
-        customAttributeModule.addSerializer(Subscription.Topic.class, new TopicSerializer());
-        customAttributeModule.addSerializer(Counts.CountItem.class, new CountItemSerializer());
-        customAttributeModule.addDeserializer(Counts.CountItem.class, new CountItemDeserializer());
-        return customAttributeModule;
-    }
+        private ObjectMapper configure(ObjectMapper om) {
+            return om.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, true)
+                    .configure(SerializationFeature.INDENT_OUTPUT, true)
+                    .configure(SerializationFeature.WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS, false)
+                    .configure(DeserializationFeature.READ_DATE_TIMESTAMPS_AS_NANOSECONDS, false)
+                    .registerModule(customAttributeModule());
+        }
 
-    private static class Holder {
-        private static final ObjectMapper INSTANCE = new ObjectMapper();
+        private SimpleModule customAttributeModule() {
+            final SimpleModule customAttributeModule = new SimpleModule(
+                    "IntercomClientModule",
+                    new Version(1, 0, 0, null, "", "")
+            );
+            customAttributeModule.addDeserializer(CustomAttribute.class, new CustomAttributeDeserializer());
+            customAttributeModule.addSerializer(CustomAttribute.class, new CustomAttributeSerializer());
+            customAttributeModule.addDeserializer(Subscription.Topic.class, new TopicDeserializer());
+            customAttributeModule.addSerializer(Subscription.Topic.class, new TopicSerializer());
+            customAttributeModule.addSerializer(Counts.CountItem.class, new CountItemSerializer());
+            customAttributeModule.addDeserializer(Counts.CountItem.class, new CountItemDeserializer());
+            return customAttributeModule;
+        }
     }
 }