issue #834 : Add NamespaceAware to abstract Model getNamespaces

Abstracts out the Model getNamespace methods to a new NamespaceAware interface that can be reused to make other code more generic

Signed-off-by: Peter Ansell <p_ansell@yahoo.com>

Author: ansell

core/model/src/main/java/org/eclipse/rdf4j/model/Model.java

@@ -28,7 +28,7 @@
  * @see org.eclipse.rdf4j.model.util.Models the Models utility class
  */
 @SuppressWarnings("deprecation")
-public interface Model extends Graph, Set<Statement>, Serializable {
+public interface Model extends Graph, Set<Statement>, Serializable, NamespaceAware {
 
 	/**
 	 * Returns an unmodifiable view of this model. This method provides "read-only" access to this model.
@@ -40,25 +40,6 @@ public interface Model extends Graph, Set<Statement>, Serializable {
 	 */
 	public Model unmodifiable();
 
-	/**
-	 * Gets the map that contains the assigned namespaces.
-	 * 
-	 * @return Map of prefix to namespace
-	 */
-	public Set<Namespace> getNamespaces();
-
-	/**
-	 * Gets the namespace that is associated with the specified prefix, if any.
-	 * 
-	 * @param prefix
-	 *        A namespace prefix.
-	 * @return The namespace name that is associated with the specified prefix, or {@link Optional#empty()} if
-	 *         there is no such namespace.
-	 */
-	public default Optional<Namespace> getNamespace(String prefix) {
-		return getNamespaces().stream().filter(t -> t.getPrefix().equals(prefix)).findAny();
-	}
-
 	/**
 	 * Sets the prefix for a namespace. This will replace any existing namespace associated to the prefix.
 	 * 

core/model/src/main/java/org/eclipse/rdf4j/model/NamespaceAware.java

@@ -0,0 +1,42 @@
+/*******************************************************************************
+ * Copyright (c) 2017 Eclipse RDF4J contributors and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Distribution License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *******************************************************************************/
+package org.eclipse.rdf4j.model;
+
+import java.util.Optional;
+import java.util.Set;
+
+/**
+ * An interface that is used to signify that something is able to provide {@link Namespace} information, in
+ * addition to {@link Statement}s.
+ * 
+ * @author Peter Ansell
+ */
+@FunctionalInterface
+public interface NamespaceAware {
+
+	/**
+	 * Gets the set that contains the assigned namespaces.
+	 * 
+	 * @return A {@link Set} containing the {@link Namespace} objects that are available.
+	 */
+	public Set<Namespace> getNamespaces();
+
+	/**
+	 * Gets the namespace that is associated with the specified prefix, if any. If multiple namespaces match
+	 * the given prefix, the result may not be consistent over successive calls to this method.
+	 * 
+	 * @param prefix
+	 *        A namespace prefix.
+	 * @return The namespace name that is associated with the specified prefix, or {@link Optional#empty()} if
+	 *         there is no such namespace.
+	 */
+	public default Optional<Namespace> getNamespace(String prefix) {
+		return getNamespaces().stream().filter(t -> t.getPrefix().equals(prefix)).findAny();
+	}
+
+}