Fix for LDAP-130, LDAP-137:

Added getObjectAttributes() method
Eliminated code duplication in getStringAttributes, getObjectAttributes and getAttributeSortedStringSet
Added AttributeValueCallbackHandler and iterator methods in LdapUtils
We are now following the same contract as Attributes and Attribute - 
if the Attribute does not exist all of the above methods now return null, if the Attribute is there but empty
the result will be an empty array or set.

core/src/main/java/org/springframework/ldap/NoSuchAttributeException.java

@@ -25,8 +25,11 @@ package org.springframework.ldap;
  */
 public class NoSuchAttributeException extends NamingException {
 
-    public NoSuchAttributeException(
-            javax.naming.directory.NoSuchAttributeException cause) {
-        super(cause);
-    }
+	public NoSuchAttributeException(String message) {
+		super(message);
+	}
+
+	public NoSuchAttributeException(javax.naming.directory.NoSuchAttributeException cause) {
+		super(cause);
+	}
 }

core/src/main/java/org/springframework/ldap/core/AttributesMapperCallbackHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2005-2007 the original author or authors.
+ * Copyright 2005-2008 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

core/src/main/java/org/springframework/ldap/core/DirContextAdapter.java

@@ -42,6 +42,7 @@ import org.apache.commons.lang.builder.EqualsBuilder;
 import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.springframework.ldap.NoSuchAttributeException;
 import org.springframework.ldap.support.LdapUtils;
 import org.springframework.util.StringUtils;
 
@@ -709,25 +710,36 @@ public class DirContextAdapter implements DirContextOperations {
 	 * (java.lang.String)
 	 */
 	public String[] getStringAttributes(String name) {
-		String[] attributes;
-
-		Attribute attribute = originalAttrs.get(name);
-		if (attribute != null && attribute.size() > 0) {
-			attributes = new String[attribute.size()];
-			for (int i = 0; i < attribute.size(); i++) {
-				try {
-					attributes[i] = (String) attribute.get(i);
-				}
-				catch (NamingException e) {
-					throw LdapUtils.convertLdapException(e);
-				}
-			}
+		try {
+			return (String[]) collectAttributeValuesAsList(name).toArray(new String[0]);
 		}
-		else {
+		catch (NoSuchAttributeException e) {
+			// The attribute does not exist - contract says to return null.
 			return null;
 		}
+	}
 
-		return attributes;
+	/*
+	 * (non-Javadoc)
+	 * 
+	 * @see
+	 * org.springframework.ldap.core.DirContextOperations#getObjectAttributes
+	 * (java.lang.String)
+	 */
+	public Object[] getObjectAttributes(String name) {
+		try {
+			return collectAttributeValuesAsList(name).toArray(new Object[0]);
+		}
+		catch (NoSuchAttributeException e) {
+			// The attribute does not exist - contract says to return null.
+			return null;
+		}
+	}
+
+	private List collectAttributeValuesAsList(String name) {
+		List list = new LinkedList();
+		LdapUtils.collectAttributeValues(originalAttrs, name, list);
+		return list;
 	}
 
 	/*
@@ -735,24 +747,15 @@ public class DirContextAdapter implements DirContextOperations {
 	 * getAttributeSortedStringSet(java.lang.String)
 	 */
 	public SortedSet getAttributeSortedStringSet(String name) {
-		TreeSet attrSet = new TreeSet();
-
-		Attribute attribute = originalAttrs.get(name);
-		if (attribute != null) {
-			for (int i = 0; i < attribute.size(); i++) {
-				try {
-					attrSet.add(attribute.get(i));
-				}
-				catch (NamingException e) {
-					throw LdapUtils.convertLdapException(e);
-				}
-			}
+		try {
+			TreeSet attrSet = new TreeSet();
+			LdapUtils.collectAttributeValues(originalAttrs, name, attrSet);
+			return attrSet;
 		}
-		else {
+		catch (NoSuchAttributeException e) {
+			// The attribute does not exist - contract says to return null.
 			return null;
 		}
-
-		return attrSet;
 	}
 
 	/**
@@ -1299,4 +1302,5 @@ public class DirContextAdapter implements DirContextOperations {
 	public boolean isReferral() {
 		return StringUtils.hasLength(referralUrl);
 	}
+
 }

core/src/main/java/org/springframework/ldap/core/DirContextOperations.java

@@ -144,16 +144,30 @@ public interface DirContextOperations extends DirContext, AttributeModifications
 	 * Get all values of a String attribute.
 	 * 
 	 * @param name name of the attribute.
-	 * 
-	 * @return all registered values of the attribute.
+	 * @return a (possibly empty) array containing all registered values of the
+	 * attribute as Strings if the attribute is defined or <code>null</code>
+	 * otherwise.
+	 * @throws ArrayStoreException if any of the attribute values is not a
+	 * String.
 	 */
 	String[] getStringAttributes(String name);
 
+	/**
+	 * Get all values of an Object attribute.
+	 * 
+	 * @param name name of the attribute.
+	 * @return a (possibly empty) array containing all registered values of the
+	 * attribute if the attribute is defined or <code>null</code> otherwise.
+	 * @since 1.3
+	 */
+	Object[] getObjectAttributes(String name);
+
 	/**
 	 * Get all String values of the attribute as a <code>SortedSet</code>.
 	 * 
 	 * @param name name of the attribute.
-	 * @return a <code>SortedSet</code> containing all values of the attribute.
+	 * @return a <code>SortedSet</code> containing all values of the attribute,
+	 * or <code>null</code> if the attribute does not exist.
 	 */
 	SortedSet getAttributeSortedStringSet(String name);
 

core/src/main/java/org/springframework/ldap/support/AttributeValueCallbackHandler.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2005-2008 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.ldap.support;
+
+/**
+ * Callback interface for use when looping through Attribute values.
+ * 
+ * @author Mattias Hellborg Arthursson
+ */
+public interface AttributeValueCallbackHandler {
+	/**
+	 * Implement to take handle one of the Attribute values.
+	 * 
+	 * @param attributeName the name of the Attribute.
+	 * @param attributeValue the value.
+	 * @param index the index of the value within the Attribute.
+	 */
+	void handleAttributeValue(String attributeName, Object attributeValue, int index);
+}

core/src/main/java/org/springframework/ldap/support/LdapUtils.java

@@ -16,12 +16,17 @@
 
 package org.springframework.ldap.support;
 
+import java.util.Collection;
+
+import javax.naming.directory.Attribute;
+import javax.naming.directory.Attributes;
 import javax.naming.directory.DirContext;
 import javax.naming.ldap.LdapContext;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.ldap.NamingException;
+import org.springframework.ldap.NoSuchAttributeException;
 import org.springframework.util.Assert;
 
 /**
@@ -65,9 +70,9 @@ public final class LdapUtils {
 	}
 
 	/**
-	 * Convert the specified checked
-	 * {@link javax.naming.NamingException NamingException} to a Spring LDAP
-	 * runtime {@link org.springframework.ldap.NamingException NamingException}
+	 * Convert the specified checked {@link javax.naming.NamingException
+	 * NamingException} to a Spring LDAP runtime
+	 * {@link org.springframework.ldap.NamingException NamingException}
 	 * equivalent.
 	 * 
 	 * @param ex the original checked NamingException to convert
@@ -127,8 +132,9 @@ public final class LdapUtils {
 			return new org.springframework.ldap.InvalidSearchFilterException(
 					(javax.naming.directory.InvalidSearchFilterException) ex);
 		}
-		
-		// this class is abstract, so it can never be of exactly this class; using instanceof
+
+		// this class is abstract, so it can never be of exactly this class;
+		// using instanceof
 		if (ex instanceof javax.naming.ldap.LdapReferralException) {
 			return new org.springframework.ldap.LdapReferralException((javax.naming.ldap.LdapReferralException) ex);
 		}
@@ -212,16 +218,74 @@ public final class LdapUtils {
 	 * Get the actual class of the supplied DirContext instance; LdapContext or
 	 * DirContext.
 	 * 
-	 * @param context
-	 *            the DirContext instance to check.
+	 * @param context the DirContext instance to check.
 	 * @return LdapContext.class if context is an LdapContext, DirContext.class
-	 *         otherwise.
+	 * otherwise.
 	 */
 	public static Class getActualTargetClass(DirContext context) {
-	    if (context instanceof LdapContext) {
-	        return LdapContext.class;
-	    }
-	
-	    return DirContext.class;
+		if (context instanceof LdapContext) {
+			return LdapContext.class;
+		}
+
+		return DirContext.class;
+	}
+
+	/**
+	 * Collect all the values of a the specified attribute from the supplied
+	 * Attributes.
+	 * 
+	 * @param attributes The Attributes; not <code>null</code>.
+	 * @param name The name of the Attribute to get values for.
+	 * @param collection the collection to collect the values in.
+	 * @throws NoSuchAttributeException if no attribute with the specified name
+	 * exists.
+	 */
+	public static void collectAttributeValues(Attributes attributes, String name, Collection collection) {
+		Assert.notNull(attributes, "Attributes must not be null");
+		Attribute attribute = attributes.get(name);
+		if (attribute == null) {
+			throw new NoSuchAttributeException("No attribute with name '" + name + "'");
+		}
+
+		iterateAttributeValues(attribute, new CollectingAttributeValueCallbackHandler(collection));
+	}
+
+	/**
+	 * Iterate through all the values of the specified Attribute calling back to
+	 * the specified callbackHandler.
+	 * @param attribute the Attribute to work with; not <code>null</code>.
+	 * @param callbackHandler the callbackHandler; not <code>null</code>.
+	 */
+	public static void iterateAttributeValues(Attribute attribute, AttributeValueCallbackHandler callbackHandler) {
+		Assert.notNull(attribute, "Attribute must not be null");
+		Assert.notNull(callbackHandler, "callbackHandler must not be null");
+
+		for (int i = 0; i < attribute.size(); i++) {
+			try {
+				callbackHandler.handleAttributeValue(attribute.getID(), attribute.get(i), i);
+			}
+			catch (javax.naming.NamingException e) {
+				throw LdapUtils.convertLdapException(e);
+			}
+		}
+	}
+
+	/**
+	 * An {@link AttributeValueCallbackHandler} to collect values in a supplied
+	 * collection.
+	 * 
+	 * @author Mattias Hellborg Arthursson
+	 */
+	private final static class CollectingAttributeValueCallbackHandler implements AttributeValueCallbackHandler {
+		private final Collection collection;
+
+		public CollectingAttributeValueCallbackHandler(Collection collection) {
+			Assert.notNull(collection, "Collection must not be null");
+			this.collection = collection;
+		}
+
+		public final void handleAttributeValue(String attributeName, Object attributeValue, int index) {
+			collection.add(attributeValue);
+		}
 	}
 }

core/src/test/java/org/springframework/ldap/core/DirContextAdapterTest.java

@@ -16,6 +16,9 @@
 
 package org.springframework.ldap.core;
 
+import java.util.Iterator;
+import java.util.SortedSet;
+
 import javax.naming.Name;
 import javax.naming.NamingException;
 import javax.naming.directory.Attribute;
@@ -107,11 +110,78 @@ public class DirContextAdapterTest extends TestCase {
 		assertEquals(2, s.length);
 	}
 
+	public void testGetStringAttributesExistsWithInvalidType() throws Exception {
+		final Attributes attrs = new BasicAttributes();
+		Attribute multi = new BasicAttribute("abc");
+		multi.add(new Object());
+		attrs.put(multi);
+		class TestableDirContextAdapter extends DirContextAdapter {
+			public TestableDirContextAdapter() {
+				super(attrs, null);
+			}
+		}
+		tested = new TestableDirContextAdapter();
+		try {
+			tested.getStringAttributes("abc");
+			fail("ClassCastException expected");
+		}
+		catch (ArrayStoreException expected) {
+			assertTrue(true);
+		}
+	}
+
+	public void testGetStringAttributesExistsEmpty() throws Exception {
+		final Attributes attrs = new BasicAttributes();
+		Attribute multi = new BasicAttribute("abc");
+		attrs.put(multi);
+		class TestableDirContextAdapter extends DirContextAdapter {
+			public TestableDirContextAdapter() {
+				super(attrs, null);
+			}
+		}
+		tested = new TestableDirContextAdapter();
+		String s[] = tested.getStringAttributes("abc");
+		assertNotNull(s);
+		assertEquals(0, s.length);
+	}
+
 	public void testGetStringAttributesNotExists() throws Exception {
 		String s[] = tested.getStringAttributes("abc");
 		assertNull(s);
 	}
 
+	public void testGetAttributesSortedStringSetExists() throws Exception {
+		final Attributes attrs = new BasicAttributes();
+		Attribute multi = new BasicAttribute("abc");
+		multi.add("123");
+		multi.add("234");
+		attrs.put(multi);
+		class TestableDirContextAdapter extends DirContextAdapter {
+			public TestableDirContextAdapter() {
+				super(attrs, null);
+			}
+		}
+		tested = new TestableDirContextAdapter();
+		SortedSet s = tested.getAttributeSortedStringSet("abc");
+		assertNotNull(s);
+		assertEquals(2, s.size());
+		Iterator it = s.iterator();
+		assertEquals("123", it.next());
+		assertEquals("234", it.next());
+	}
+
+	public void testGetAttributesSortedStringSetNotExists() throws Exception {
+		final Attributes attrs = new BasicAttributes();
+		class TestableDirContextAdapter extends DirContextAdapter {
+			public TestableDirContextAdapter() {
+				super(attrs, null);
+			}
+		}
+		tested = new TestableDirContextAdapter();
+		SortedSet s = tested.getAttributeSortedStringSet("abc");
+		assertNull(s);
+	}
+
 	public void testAddAttributeValue() throws NamingException {
 		// Perform test
 		tested.addAttributeValue("abc", "123");
@@ -653,7 +723,7 @@ public class DirContextAdapterTest extends TestCase {
 		}
 		tested = new TestableDirContextAdapter();
 		assertTrue(tested.isUpdateMode());
-		tested.setAttributeValues("title", new String[] {"Jim", "George", "Juergen" }, true);
+		tested.setAttributeValues("title", new String[] { "Jim", "George", "Juergen" }, true);
 
 		// change
 		ModificationItem[] mods = tested.getModificationItems();

core/src/test/java/org/springframework/ldap/support/LdapUtilsTest.java

@@ -0,0 +1,92 @@
+package org.springframework.ldap.support;
+
+import java.util.LinkedList;
+
+import javax.naming.directory.BasicAttribute;
+import javax.naming.directory.BasicAttributes;
+
+import junit.framework.TestCase;
+
+import org.easymock.MockControl;
+import org.springframework.ldap.NoSuchAttributeException;
+
+public class LdapUtilsTest extends TestCase {
+
+	private MockControl handlerControl;
+
+	private AttributeValueCallbackHandler handlerMock;
+
+	protected void setUp() throws Exception {
+		super.setUp();
+
+		handlerControl = MockControl.createControl(AttributeValueCallbackHandler.class);
+		handlerMock = (AttributeValueCallbackHandler) handlerControl.getMock();
+	}
+
+	protected void tearDown() throws Exception {
+		super.tearDown();
+
+		handlerControl = null;
+		handlerMock = null;
+	}
+
+	public void testCollectAttributeValues() {
+		String expectedAttributeName = "someAttribute";
+		BasicAttribute expectedAttribute = new BasicAttribute(expectedAttributeName);
+		expectedAttribute.add("value1");
+		expectedAttribute.add("value2");
+
+		BasicAttributes attributes = new BasicAttributes();
+		attributes.put(expectedAttribute);
+
+		LinkedList list = new LinkedList();
+		LdapUtils.collectAttributeValues(attributes, expectedAttributeName, list);
+
+		assertEquals(2, list.size());
+		assertEquals("value1", list.get(0));
+		assertEquals("value2", list.get(1));
+	}
+
+	public void testCollectAttributeValuesThrowsExceptionWhenAttributeNotPresent() {
+		String expectedAttributeName = "someAttribute";
+		BasicAttributes attributes = new BasicAttributes();
+
+		LinkedList list = new LinkedList();
+		try {
+			LdapUtils.collectAttributeValues(attributes, expectedAttributeName, list);
+			fail("NoSuchAttributeException expected");
+		}
+		catch (NoSuchAttributeException expected) {
+			assertTrue(true);
+		}
+	}
+
+	public void testIterateAttributeValues() {
+		String expectedAttributeName = "someAttribute";
+
+		BasicAttribute expectedAttribute = new BasicAttribute(expectedAttributeName);
+		expectedAttribute.add("value1");
+		expectedAttribute.add("value2");
+
+		handlerMock.handleAttributeValue(expectedAttributeName, "value1", 0);
+		handlerMock.handleAttributeValue(expectedAttributeName, "value2", 1);
+
+		handlerControl.replay();
+
+		LdapUtils.iterateAttributeValues(expectedAttribute, handlerMock);
+
+		handlerControl.verify();
+	}
+
+	public void testIterateAttributeValuesWithEmptyAttribute() {
+		String expectedAttributeName = "someAttribute";
+
+		BasicAttribute expectedAttribute = new BasicAttribute(expectedAttributeName);
+
+		handlerControl.replay();
+
+		LdapUtils.iterateAttributeValues(expectedAttribute, handlerMock);
+
+		handlerControl.verify();
+	}
+}