Add a configuration to inhibit the rendering of an empty 'attributes'

src/main/java/com/github/jasminb/jsonapi/ResourceConverter.java

@@ -812,7 +812,6 @@ private ObjectNode getDataNode(Object object, Map<String, ObjectNode> includedCo
 			// Cache the object for recursion breaking purposes
 			resourceCache.cache(resourceId.concat(configuration.getTypeName(object.getClass())), null);
 		}
-		dataNode.set(ATTRIBUTES, attributesNode);
 
 		// Handle relationships (remove from base type and add as relationships)
 		List<Field> relationshipFields = configuration.getRelationshipFields(object.getClass());
@@ -916,6 +915,20 @@ private ObjectNode getDataNode(Object object, Map<String, ObjectNode> includedCo
 			}
 		}
 
+		// Note: Attributes can be rendered once all other top
+		//       level object properties have been removed.
+		//       If done earlier, the presence of these properties
+		//       will cause the isEmpty test to fail in the case
+		//       of a configuration disallowing an empty
+		//       'attributes' tag to be rendered.
+		if (canSerializeEmptyAttributesTag(settings)) {
+			dataNode.set(ATTRIBUTES, attributesNode); // default
+		} else {
+			if (!attributesNode.isEmpty(null)) {
+				dataNode.set(ATTRIBUTES, attributesNode);
+			}
+		}
+
 		if (jsonLinks != null) {
 			dataNode.set(LINKS, jsonLinks);
 		}
@@ -1232,6 +1245,13 @@ private boolean shouldSerializeMeta(SerializationSettings settings) {
 		return serializationFeatures.contains(SerializationFeature.INCLUDE_META);
 	}
 
+	private boolean canSerializeEmptyAttributesTag(SerializationSettings settings) {
+	  if (settings != null && settings.serializeEmptyAttributesTag() != null) {
+		  return settings.serializeEmptyAttributesTag();
+	  }
+	  return serializationFeatures.contains(SerializationFeature.ATTRIBUTES_TAG_ONLY_IF_NOT_EMPTY);
+	}
+
 	private JsonNode removeField(ObjectNode node, Field field) {
 		if (field != null) {
 			return node.remove(namingStrategy.nameForField(null, null, field.getName()));

src/main/java/com/github/jasminb/jsonapi/SerializationFeature.java

@@ -24,10 +24,17 @@ public enum SerializationFeature {
 	/**
 	 * If enabled, links attribute will be serialized
 	 */
-	INCLUDE_LINKS(true);
+	INCLUDE_LINKS(true),
+
+	/**
+	 * If enabled, resources that only have
+	 * type and id will not render the attributes property.
+	 */
+	ATTRIBUTES_TAG_ONLY_IF_NOT_EMPTY(false);
 
 	final boolean enabled;
 
+
 	SerializationFeature(boolean enabled) {
 		this.enabled = enabled;
 	}

src/main/java/com/github/jasminb/jsonapi/SerializationSettings.java

@@ -13,6 +13,7 @@ public class SerializationSettings {
 	private List<String> relationshipExludes;
 	private Boolean serializeMeta;
 	private Boolean serializeLinks;
+	private Boolean serializeEmptyAttributesTag = true;
 
 	private SerializationSettings() {
 		// Hide CTOR
@@ -52,6 +53,10 @@ public Boolean serializeLinks() {
 		return serializeLinks;
 	}
 
+	public Boolean serializeEmptyAttributesTag() {
+		return serializeEmptyAttributesTag;
+	}
+
 	/**
 	 * Serialisation settings builder.
 	 */
@@ -60,6 +65,7 @@ public static class Builder {
 		private List<String> relationshipExludes = new ArrayList<>();
 		private Boolean serializeMeta;
 		private Boolean serializeLinks;
+		private Boolean serializeEmptyAttributesTag;
 
 		/**
 		 * Explicitly enable relationship serialisation.
@@ -70,7 +76,7 @@ public Builder includeRelationship(String relationshipName) {
 			relationshipIncludes.add(relationshipName);
 			return this;
 		}
-		
+
 		/**
 		 * Explicitly disable relationship serialisation.
 		 * @param relationshipName {@link String} relationship name
@@ -100,6 +106,11 @@ public Builder serializeLinks(Boolean flag) {
 			serializeLinks = flag;
 			return this;
 		}
+
+		public Builder serializeEmptyAttributesTag(Boolean flag) {
+			serializeEmptyAttributesTag = flag;
+			return this;
+		}
 
 		/**
 		 * Create new SerialisationSettings instance.
@@ -111,6 +122,7 @@ public SerializationSettings build() {
 			result.relationshipExludes = new ArrayList<>(relationshipExludes);
 			result.serializeLinks = serializeLinks;
 			result.serializeMeta = serializeMeta;
+			result.serializeEmptyAttributesTag = serializeEmptyAttributesTag;
 			return result;
 		}
 	}

src/test/java/com/github/jasminb/jsonapi/SerializationTest.java

@@ -1,18 +1,23 @@
 package com.github.jasminb.jsonapi;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.PropertyNamingStrategy;
 import com.github.jasminb.jsonapi.exceptions.DocumentSerializationException;
 import com.github.jasminb.jsonapi.models.Article;
 import com.github.jasminb.jsonapi.models.Author;
+import com.github.jasminb.jsonapi.models.IntegerIdResource;
 import com.github.jasminb.jsonapi.models.SimpleMeta;
+import com.github.jasminb.jsonapi.models.SimpleResource;
 import com.github.jasminb.jsonapi.models.Status;
 import com.github.jasminb.jsonapi.models.User;
 import com.github.jasminb.jsonapi.models.errors.Error;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -127,6 +132,22 @@ public void testIncludedDataDisabledTroughSettings() throws DocumentSerializatio
 		Assert.assertNull(status.getContent());
 	}
 
+	@Test
+	public void testEnableNonEmptyAttributesTagThroughSettings() throws Exception {
+		SimpleResource source = new SimpleResource();
+		source.setId(80085);
+		JSONAPIDocument<SimpleResource> document = new JSONAPIDocument<>(source);
+
+		SerializationSettings serializationSettings = new SerializationSettings.Builder()
+				.serializeEmptyAttributesTag(false )
+				.build();
+
+		converter.registerType(SimpleResource.class);
+		String s = new String( converter.writeDocument(document, serializationSettings) );
+		ObjectMapper m = new ObjectMapper();
+		Assert.assertNull( m.readTree(s.getBytes()).get("attributes"));
+	}
+
 	/**
 	 * Covers use-case where global settings are used to disable relationship attribute inclusion but
 	 * behaviour is changed trouh local settings provided when serialization is executed.
@@ -136,18 +157,18 @@ public void testIncludedDataDisabledTroughSettings() throws DocumentSerializatio
 	public void testIncludedDataEnabledTroughSettings() throws DocumentSerializationException {
 		converter.disableSerializationOption(SerializationFeature.INCLUDE_RELATIONSHIP_ATTRIBUTES);
 		JSONAPIDocument<User> document = createDocument(createUser());
-		
+
 		SerializationSettings serializationSettings = new SerializationSettings.Builder()
 				.includeRelationship("statuses")
 				.build();
-		
+
 		JSONAPIDocument<User> convertedBack = converter.readDocument(
 				converter.writeDocument(document, serializationSettings), User.class);
-		
+
 		Status status = convertedBack.get().getStatuses().iterator().next();
 		Assert.assertNotNull(status.getContent());
 	}
-	
+
 	@Test
 	public void testOverrideGlobalMetaLinksSettings() throws DocumentSerializationException {
 		JSONAPIDocument<User> document = createDocument(createUser());

src/test/java/com/github/jasminb/jsonapi/models/SimpleResource.java

@@ -0,0 +1,26 @@
+package com.github.jasminb.jsonapi.models;
+
+import com.github.jasminb.jsonapi.IntegerIdHandler;
+import com.github.jasminb.jsonapi.annotations.Id;
+import com.github.jasminb.jsonapi.annotations.Type;
+
+/**
+ * Model class used to test {@link Integer} as resource identifier.
+ *
+ * @author jbegic
+ */
+@Type("simple-resource-type")
+public class SimpleResource {
+
+	@Id(IntegerIdHandler.class)
+	private Integer id;
+
+	public Integer getId() {
+		return id;
+	}
+
+	public void setId(Integer id) {
+		this.id = id;
+	}
+
+}