Merge pull request #136 from bsara/master

Jackson mapper default property inclusion should be "ALWAYS" to prevent null values from being omitted in query results

Author: oliemansm

src/main/java/graphql/servlet/GraphQLObjectMapper.java

@@ -1,5 +1,6 @@
 package graphql.servlet;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.MappingIterator;
@@ -43,8 +44,10 @@ public ObjectMapper getJacksonMapper() {
         if (result == null) { // First check (no locking)
             synchronized(this) {
                 result = mapper;
-                if (result == null) // Second check (with locking)
-                    mapper = result = objectMapperProvider.provide();
+                if (result == null) { // Second check (with locking)
+                    mapper = result = objectMapperProvider.provide().copy();
+                    mapper.setDefaultPropertyInclusion(JsonInclude.Include.ALWAYS);
+                }
             }
         }