API to configure custom default identity strategy for collection items

src/integration-test/java/de/danielbechler/diff/identity/IdentityStrategyAT.groovy

@@ -65,4 +65,23 @@ class IdentityStrategyAT extends Specification {
 		then:
 		  node.untouched
 	}
+
+	def 'configure custom IdentityStrategyResolver'() {
+		given:
+		  def strategy = new IdentityStrategy() {
+
+			  boolean equals(Object working, Object base) {
+				  return working.getAt('id') == base.getAt('id')
+			  }
+		  }
+		  def objectDiffer = ObjectDifferBuilder.startBuilding()
+				  .identity()
+				  .setDefaultCollectionItemIdentityStrategy(strategy)
+				  .and()
+				  .build()
+		when:
+		  def node = objectDiffer.compare([[id: '1', value: 'original']], [[id: '1', value: 'changed']])
+		then:
+		  node.getChild(NodePath.startBuilding().collectionItem([id:'1']).build()).changed
+	}
 }

src/main/java/de/danielbechler/diff/identity/CollectionItemIdentityService.java

@@ -19,14 +19,16 @@
 import de.danielbechler.diff.inclusion.ValueNode;
 import de.danielbechler.diff.node.DiffNode;
 import de.danielbechler.diff.path.NodePath;
+import de.danielbechler.util.Assert;
 
 class CollectionItemIdentityService implements IdentityStrategyResolver
 {
 	private final ValueNode<IdentityStrategy> nodePathIdentityStrategies;
 	private final TypePropertyIdentityStrategyResolver typePropertyIdentityStrategyResolver;
 	private final IdentityConfigurer identityConfigurer;
+	private IdentityStrategy defaultIdentityStrategy = EqualsIdentityStrategy.getInstance();
 
-	public CollectionItemIdentityService(final IdentityConfigurer identityConfigurer)
+	CollectionItemIdentityService(final IdentityConfigurer identityConfigurer)
 	{
 		this.identityConfigurer = identityConfigurer;
 		this.nodePathIdentityStrategies = new ValueNode<IdentityStrategy>();
@@ -45,24 +47,31 @@ public IdentityStrategy resolveIdentityStrategy(final DiffNode node)
 		{
 			return identityStrategy;
 		}
-		return EqualsIdentityStrategy.getInstance();
+		return defaultIdentityStrategy;
 	}
 
-	public IdentityConfigurer.OfCollectionItems ofCollectionItems(final NodePath nodePath)
+	IdentityConfigurer.OfCollectionItems ofCollectionItems(final NodePath nodePath)
 	{
 		return new OfCollectionItemsByNodePath(nodePath);
 	}
 
-	public IdentityConfigurer.OfCollectionItems ofCollectionItems(final Class<?> type, final String propertyName)
+	IdentityConfigurer.OfCollectionItems ofCollectionItems(final Class<?> type, final String propertyName)
 	{
 		return new OfCollectionItemsByTypeProperty(type, propertyName);
 	}
 
+	IdentityConfigurer setDefaultIdentityStrategy(final IdentityStrategy identityStrategy)
+	{
+		Assert.notNull(identityStrategy, "identityStrategy");
+		this.defaultIdentityStrategy = identityStrategy;
+		return identityConfigurer;
+	}
+
 	private class OfCollectionItemsByNodePath implements IdentityConfigurer.OfCollectionItems
 	{
 		private final NodePath nodePath;
 
-		public OfCollectionItemsByNodePath(final NodePath nodePath)
+		OfCollectionItemsByNodePath(final NodePath nodePath)
 		{
 			this.nodePath = nodePath;
 		}
@@ -79,7 +88,7 @@ private class OfCollectionItemsByTypeProperty implements IdentityConfigurer.OfCo
 		private final Class<?> type;
 		private final String propertyName;
 
-		public OfCollectionItemsByTypeProperty(final Class<?> type, final String propertyName)
+		OfCollectionItemsByTypeProperty(final Class<?> type, final String propertyName)
 		{
 			this.type = type;
 			this.propertyName = propertyName;

src/main/java/de/danielbechler/diff/identity/IdentityConfigurer.java

@@ -31,6 +31,8 @@ public interface IdentityConfigurer
 	 */
 	OfCollectionItems ofCollectionItems(Class<?> type, String propertyName);
 
+	IdentityConfigurer setDefaultCollectionItemIdentityStrategy(IdentityStrategy identityStrategy);
+
 	ObjectDifferBuilder and();
 
 	interface OfCollectionItems

src/main/java/de/danielbechler/diff/identity/IdentityService.java

@@ -40,6 +40,11 @@ public OfCollectionItems ofCollectionItems(final Class<?> type, final String pro
 		return collectionItemIdentityService.ofCollectionItems(type, propertyName);
 	}
 
+	public IdentityConfigurer setDefaultCollectionItemIdentityStrategy(final IdentityStrategy identityStrategy)
+	{
+		return collectionItemIdentityService.setDefaultIdentityStrategy(identityStrategy);
+	}
+
 	public IdentityStrategy resolveIdentityStrategy(final DiffNode node)
 	{
 		return collectionItemIdentityService.resolveIdentityStrategy(node);