CollectionCollection/MapToMapConverter preserve original Collection/Map if no converted elements (SPR-8714)

org.springframework.core/src/main/java/org/springframework/core/convert/TypeDescriptor.java

@@ -281,7 +281,7 @@ public class TypeDescriptor {
 	 */
 	public TypeDescriptor getElementTypeDescriptor(Object element) {
 		TypeDescriptor elementType = getElementTypeDescriptor();
-		return (elementType != TypeDescriptor.UNKNOWN ? elementType : forObject(element));
+		return (!TypeDescriptor.UNKNOWN.equals(elementType) ? elementType : forObject(element));
 	}
 
 	/**

org.springframework.core/src/main/java/org/springframework/core/convert/support/ArrayToCollectionConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2011 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.
@@ -49,7 +49,8 @@ final class ArrayToCollectionConverter implements ConditionalGenericConverter {
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		return ConversionUtils.canConvertElements(sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(), this.conversionService);
+		return ConversionUtils.canConvertElements(
+				sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(), this.conversionService);
 	}
 
 	@SuppressWarnings("unchecked")
@@ -58,12 +59,21 @@ final class ArrayToCollectionConverter implements ConditionalGenericConverter {
 			return null;
 		}		
 		int length = Array.getLength(source);
-		Collection target = CollectionFactory.createCollection(targetType.getType(), length);
-		for (int i = 0; i < length; i++) {
-			Object sourceElement = Array.get(source, i);
-			Object targetElement = this.conversionService.convert(sourceElement, sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(sourceElement));
-			target.add(targetElement);
+		Collection<Object> target = CollectionFactory.createCollection(targetType.getType(), length);
+		if (targetType.getElementTypeDescriptor() == null) {
+			for (int i = 0; i < length; i++) {
+				Object sourceElement = Array.get(source, i);
+				target.add(sourceElement);
+			}
 		}
+		else {
+			for (int i = 0; i < length; i++) {
+				Object sourceElement = Array.get(source, i);
+				Object targetElement = this.conversionService.convert(sourceElement,
+						sourceType.getElementTypeDescriptor(sourceElement), targetType.getElementTypeDescriptor());
+				target.add(targetElement);
+			}
+		}		
 		return target;
 	}
 

org.springframework.core/src/main/java/org/springframework/core/convert/support/CollectionToCollectionConverter.java

@@ -49,7 +49,8 @@ final class CollectionToCollectionConverter implements ConditionalGenericConvert
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		return ConversionUtils.canConvertElements(sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(), conversionService);
+		return ConversionUtils.canConvertElements(
+				sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(), this.conversionService);
 	}
 
 	@SuppressWarnings("unchecked")
@@ -57,15 +58,25 @@ final class CollectionToCollectionConverter implements ConditionalGenericConvert
 		if (source == null) {
 			return null;
 		}
+		boolean copyRequired = !targetType.getType().isInstance(source);
 		Collection<?> sourceCollection = (Collection<?>) source;
-		Collection target = CollectionFactory.createCollection(targetType.getType(), sourceCollection.size());
-		for (Object sourceElement : sourceCollection) {
-			Object targetElement = this.conversionService.convert(sourceElement,
-					sourceType.getElementTypeDescriptor(sourceElement),
-					targetType.getElementTypeDescriptor(sourceElement));
-			target.add(targetElement);
+		Collection<Object> target = CollectionFactory.createCollection(targetType.getType(), sourceCollection.size());
+		if (targetType.getElementTypeDescriptor() == null) {
+			for (Object element : sourceCollection) {
+				target.add(element);
+			}
 		}
-		return target;
+		else {
+			for (Object sourceElement : sourceCollection) {
+				Object targetElement = this.conversionService.convert(sourceElement,
+						sourceType.getElementTypeDescriptor(sourceElement), targetType.getElementTypeDescriptor());
+				target.add(targetElement);
+				if (sourceElement != targetElement) {
+					copyRequired = true;
+				}
+			}
+		}
+		return (copyRequired ? target : source);
 	}
 
 }

org.springframework.core/src/main/java/org/springframework/core/convert/support/GenericConversionService.java

@@ -148,7 +148,8 @@ public class GenericConversionService implements ConversionService, ConverterReg
 		Assert.isTrue(source == null || sourceType.getObjectType().isInstance(source));
 		GenericConverter converter = getConverter(sourceType, targetType);
 		if (converter == null) {
-			if (source == null || targetType.getObjectType().isInstance(source)) {
+			if (source == null ||
+					(sourceType.isAssignableTo(targetType) && targetType.getObjectType().isInstance(source))) {
 				return source;
 			}
 			else {

org.springframework.core/src/main/java/org/springframework/core/convert/support/MapToMapConverter.java

@@ -49,8 +49,7 @@ final class MapToMapConverter implements ConditionalGenericConverter {
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		return this.conversionService.canConvert(sourceType.getMapKeyTypeDescriptor(), targetType.getMapKeyTypeDescriptor()) && 
-			this.conversionService.canConvert(sourceType.getMapValueTypeDescriptor(), targetType.getMapValueTypeDescriptor());
+		return canConvertKey(sourceType, targetType) && canConvertValue(sourceType, targetType);
 	}
 
 	@SuppressWarnings("unchecked")
@@ -58,21 +57,46 @@ final class MapToMapConverter implements ConditionalGenericConverter {
 		if (source == null) {
 			return null;
 		}
-		Map<?, ?> sourceMap = (Map<?, ?>) source;
-		Map targetMap = CollectionFactory.createMap(targetType.getType(), sourceMap.size());
-		for (Object entry : sourceMap.entrySet()) {
-			Map.Entry sourceMapEntry = (Map.Entry) entry;
-			Object sourceKey = sourceMapEntry.getKey();
-			Object sourceValue = sourceMapEntry.getValue();
-			Object targetKey = this.conversionService.convert(sourceKey,
-					sourceType.getMapKeyTypeDescriptor(sourceKey),
-					targetType.getMapKeyTypeDescriptor(sourceKey));
-			Object targetValue = this.conversionService.convert(sourceValue,
-					sourceType.getMapValueTypeDescriptor(sourceValue),
-					targetType.getMapValueTypeDescriptor(sourceValue));
+		boolean copyRequired = !targetType.getType().isInstance(source);
+		Map<Object, Object> sourceMap = (Map<Object, Object>) source;
+		Map<Object, Object> targetMap = CollectionFactory.createMap(targetType.getType(), sourceMap.size());
+		for (Map.Entry<Object, Object> entry : sourceMap.entrySet()) {
+			Object sourceKey = entry.getKey();
+			Object sourceValue = entry.getValue();
+			Object targetKey = convertKey(sourceKey, sourceType, targetType.getMapKeyTypeDescriptor());
+			Object targetValue = convertValue(sourceValue, sourceType, targetType.getMapValueTypeDescriptor());
 			targetMap.put(targetKey, targetValue);
+			if (sourceKey != targetKey || sourceValue != targetValue) {
+				copyRequired = true;
+			}
 		}
-		return targetMap;
+		return (copyRequired ? targetMap : sourceMap);
 	}
-	
+
+	// internal helpers
+
+	private boolean canConvertKey(TypeDescriptor sourceType, TypeDescriptor targetType) {
+		return ConversionUtils.canConvertElements(sourceType.getMapKeyTypeDescriptor(),
+				targetType.getMapKeyTypeDescriptor(), this.conversionService);
+	}
+
+	private boolean canConvertValue(TypeDescriptor sourceType, TypeDescriptor targetType) {
+		return ConversionUtils.canConvertElements(sourceType.getMapValueTypeDescriptor(),
+				targetType.getMapValueTypeDescriptor(), this.conversionService);
+	}
+
+	private Object convertKey(Object sourceKey, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (targetType == null) {
+			return sourceKey;
+		}
+		return this.conversionService.convert(sourceKey, sourceType.getMapKeyTypeDescriptor(sourceKey), targetType);
+	}
+
+	private Object convertValue(Object sourceValue, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (targetType == null) {
+			return sourceValue;
+		}
+		return this.conversionService.convert(sourceValue, sourceType.getMapValueTypeDescriptor(sourceValue), targetType);
+	}
+
 }

org.springframework.core/src/test/java/org/springframework/core/convert/support/CollectionToCollectionConverterTests.java

@@ -0,0 +1,295 @@
+/*
+ * Copyright 2002-2011 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.core.convert.support;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URI;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Vector;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.core.convert.ConversionFailedException;
+import org.springframework.core.convert.ConverterNotFoundException;
+import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.FileSystemResource;
+import org.springframework.core.io.Resource;
+
+import static org.junit.Assert.*;
+
+/**
+ * @author Keith Donald
+ */
+public class CollectionToCollectionConverterTests {
+
+	private GenericConversionService conversionService = new GenericConversionService();
+
+	@Before
+	public void setUp() {
+		conversionService.addConverter(new CollectionToCollectionConverter(conversionService));
+	}
+
+	@Test
+	public void scalarList() throws Exception {
+		List<String> list = new ArrayList<String>();
+		list.add("9");
+		list.add("37");
+		TypeDescriptor sourceType = TypeDescriptor.forObject(list);
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("scalarListTarget"));
+		assertFalse(conversionService.canConvert(sourceType, targetType));
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		@SuppressWarnings("unchecked")		
+		List<String> result = (List<String>) conversionService.convert(list, sourceType, targetType);
+		assertFalse(list.equals(result));
+		assertEquals((Integer) 9, result.get(0));
+		assertEquals((Integer) 37, result.get(1));
+	}
+	
+	public ArrayList<Integer> scalarListTarget;
+
+	@Test
+	public void emptyListToList() throws Exception {
+		conversionService.addConverter(new CollectionToCollectionConverter(conversionService));
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		List<String> list = new ArrayList<String>();
+		TypeDescriptor sourceType = TypeDescriptor.forObject(list);
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("emptyListTarget"));
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		assertEquals(list, conversionService.convert(list, sourceType, targetType));
+	}
+
+	public List<Integer> emptyListTarget;
+
+	@Test
+	public void emptyListToListDifferentTargetType() throws Exception {
+		conversionService.addConverter(new CollectionToCollectionConverter(conversionService));
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		List<String> list = new ArrayList<String>();
+		TypeDescriptor sourceType = TypeDescriptor.forObject(list);
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("emptyListDifferentTarget"));
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		@SuppressWarnings("unchecked")
+		LinkedList<Integer> result = (LinkedList<Integer>) conversionService.convert(list, sourceType, targetType);
+		assertEquals(LinkedList.class, result.getClass());
+		assertTrue(result.isEmpty());
+	}
+
+	public LinkedList<Integer> emptyListDifferentTarget;
+
+	@Test
+	public void collectionToObjectInteraction() throws Exception {
+		List<List<String>> list = new ArrayList<List<String>>();
+		list.add(Arrays.asList("9", "12"));
+		list.add(Arrays.asList("37", "23"));
+		conversionService.addConverter(new CollectionToObjectConverter(conversionService));
+		assertTrue(conversionService.canConvert(List.class, List.class));
+		assertSame(list, conversionService.convert(list, List.class));
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void arrayCollectionToObjectInteraction() throws Exception {
+		List<String>[] array = new List[2];
+		array[0] = Arrays.asList("9", "12");
+		array[1] = Arrays.asList("37", "23");
+		conversionService.addConverter(new ArrayToCollectionConverter(conversionService));
+		conversionService.addConverter(new CollectionToObjectConverter(conversionService));
+		assertTrue(conversionService.canConvert(String[].class, List.class));
+		assertEquals(Arrays.asList(array), conversionService.convert(array, List.class));
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void objectToCollection() throws Exception {
+		List<List<String>> list = new ArrayList<List<String>>();
+		list.add(Arrays.asList("9", "12"));
+		list.add(Arrays.asList("37", "23"));
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		conversionService.addConverter(new ObjectToCollectionConverter(conversionService));
+		conversionService.addConverter(new CollectionToObjectConverter(conversionService));
+		TypeDescriptor sourceType = TypeDescriptor.forObject(list);
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("objectToCollection"));
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		List<List<List<Integer>>> result = (List<List<List<Integer>>>) conversionService.convert(list, sourceType, targetType);
+		assertEquals((Integer)9, result.get(0).get(0).get(0));
+		assertEquals((Integer)12, result.get(0).get(1).get(0));
+		assertEquals((Integer)37, result.get(1).get(0).get(0));
+		assertEquals((Integer)23, result.get(1).get(1).get(0));
+	}
+
+	public List<List<List<Integer>>> objectToCollection;
+	
+	@Test
+	@SuppressWarnings("unchecked")
+	public void stringToCollection() throws Exception {
+		List<List<String>> list = new ArrayList<List<String>>();
+		list.add(Arrays.asList("9,12"));
+		list.add(Arrays.asList("37,23"));
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		conversionService.addConverter(new StringToCollectionConverter(conversionService));
+		conversionService.addConverter(new ObjectToCollectionConverter(conversionService));
+		conversionService.addConverter(new CollectionToObjectConverter(conversionService));
+		TypeDescriptor sourceType = TypeDescriptor.forObject(list);
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("objectToCollection"));
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		List<List<List<Integer>>> result = (List<List<List<Integer>>>) conversionService.convert(list, sourceType, targetType);
+		assertEquals((Integer)9, result.get(0).get(0).get(0));
+		assertEquals((Integer)12, result.get(0).get(0).get(1));
+		assertEquals((Integer)37, result.get(1).get(0).get(0));
+		assertEquals((Integer)23, result.get(1).get(0).get(1));
+	}
+
+	@Test
+	public void differentImpls() throws Exception {
+		List<Resource> resources = new ArrayList<Resource>();
+		resources.add(new ClassPathResource("test"));
+		resources.add(new FileSystemResource("test"));
+		resources.add(new TestResource());
+		TypeDescriptor sourceType = TypeDescriptor.forObject(resources);
+		assertSame(resources, conversionService.convert(resources, sourceType, new TypeDescriptor(getClass().getField("resources"))));
+	}
+
+	@Test
+	public void mixedInNulls() throws Exception {
+		List<Resource> resources = new ArrayList<Resource>();
+		resources.add(new ClassPathResource("test"));
+		resources.add(null);
+		resources.add(new FileSystemResource("test"));
+		resources.add(new TestResource());
+		TypeDescriptor sourceType = TypeDescriptor.forObject(resources);
+		assertSame(resources, conversionService.convert(resources, sourceType, new TypeDescriptor(getClass().getField("resources"))));
+	}
+
+	@Test
+	public void allNulls() throws Exception {
+		List<Resource> resources = new ArrayList<Resource>();
+		resources.add(null);
+		resources.add(null);
+		TypeDescriptor sourceType = TypeDescriptor.forObject(resources);
+		assertSame(resources, conversionService.convert(resources, sourceType, new TypeDescriptor(getClass().getField("resources"))));
+	}
+
+	@Test(expected=ConverterNotFoundException.class)
+	public void elementTypesNotConvertible() throws Exception {
+		List<String> resources = new ArrayList<String>();
+		resources.add(null);
+		resources.add(null);
+		TypeDescriptor sourceType = new TypeDescriptor(getClass().getField("strings"));
+		assertEquals(resources, conversionService.convert(resources, sourceType, new TypeDescriptor(getClass().getField("resources"))));
+	}
+	
+	public List<String> strings;
+
+	@Test(expected=ConversionFailedException.class)
+	public void nothingInCommon() throws Exception {
+		List<Object> resources = new ArrayList<Object>();
+		resources.add(new ClassPathResource("test"));
+		resources.add(3);
+		TypeDescriptor sourceType = TypeDescriptor.forObject(resources);
+		assertEquals(resources, conversionService.convert(resources, sourceType, new TypeDescriptor(getClass().getField("resources"))));
+	}
+
+	public List<Resource> resources;
+
+	public static abstract class BaseResource implements Resource {
+
+		public InputStream getInputStream() throws IOException {
+			return null;
+		}
+
+		public boolean exists() {
+			return false;
+		}
+
+		public boolean isReadable() {
+			return false;
+		}
+
+		public boolean isOpen() {
+			return false;
+		}
+
+		public URL getURL() throws IOException {
+			return null;
+		}
+
+		public URI getURI() throws IOException {
+			return null;
+		}
+
+		public File getFile() throws IOException {
+			return null;
+		}
+
+		public long contentLength() throws IOException {
+			return 0;
+		}
+
+		public long lastModified() throws IOException {
+			return 0;
+		}
+
+		public Resource createRelative(String relativePath) throws IOException {
+			return null;
+		}
+
+		public String getFilename() {
+			return null;
+		}
+
+		public String getDescription() {
+			return null;
+		}
+	}
+	
+	public static class TestResource extends BaseResource {
+		
+	}
+
+	@Test
+	public void convertEmptyVector_shouldReturnEmptyArrayList() {
+		Vector<String> vector = new Vector<String>();
+		vector.add("Element");
+		testCollectionConversionToArrayList(vector);
+	}
+
+	@Test
+	public void convertNonEmptyVector_shouldReturnNonEmptyArrayList() {
+		Vector<String> vector = new Vector<String>();
+		vector.add("Element");
+		testCollectionConversionToArrayList(vector);
+	}
+
+	@SuppressWarnings("rawtypes")
+	private void testCollectionConversionToArrayList(Collection<String> aSource) {
+		Object myConverted = (new CollectionToCollectionConverter(new GenericConversionService())).convert(
+				aSource, TypeDescriptor.forObject(aSource), TypeDescriptor.forObject(new ArrayList()));
+		assertTrue(myConverted instanceof ArrayList<?>);
+		assertEquals(aSource.size(), ((ArrayList<?>) myConverted).size());
+	}
+
+}

org.springframework.core/src/test/java/org/springframework/core/convert/support/MapToMapConverterTests.java

@@ -0,0 +1,186 @@
+/*
+ * Copyright 2002-2011 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.core.convert.support;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.core.convert.ConversionFailedException;
+import org.springframework.core.convert.ConverterNotFoundException;
+import org.springframework.core.convert.TypeDescriptor;
+
+import static org.junit.Assert.*;
+
+public class MapToMapConverterTests {
+
+	private GenericConversionService conversionService = new GenericConversionService();
+
+	@Before
+	public void setUp() {
+		conversionService.addConverter(new MapToMapConverter(conversionService));
+	}
+
+	@Test
+	public void scalarMap() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("1", "9");
+		map.put("2", "37");
+		TypeDescriptor sourceType = TypeDescriptor.forObject(map);
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("scalarMapTarget"));
+		assertFalse(conversionService.canConvert(sourceType, targetType));
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		@SuppressWarnings("unchecked")		
+		Map<Integer, Integer> result = (Map<Integer, Integer>) conversionService.convert(map, sourceType, targetType);
+		assertFalse(map.equals(result));
+		assertEquals((Integer) 9, result.get(1));
+		assertEquals((Integer) 37, result.get(2));
+	}
+
+	public Map<Integer, Integer> scalarMapTarget;
+
+	@Test
+	public void scalarMapNotGenericTarget() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("1", "9");
+		map.put("2", "37");
+		assertTrue(conversionService.canConvert(Map.class, Map.class));
+		assertSame(map, conversionService.convert(map, Map.class));
+	}
+
+	@Test
+	public void scalarMapNotGenericSourceField() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("1", "9");
+		map.put("2", "37");
+		TypeDescriptor sourceType = new TypeDescriptor(getClass().getField("notGenericMapSource"));
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("scalarMapTarget"));
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		try {
+			conversionService.convert(map, sourceType, targetType);
+		} catch (ConversionFailedException e) {
+			assertTrue(e.getCause() instanceof ConverterNotFoundException);
+		}
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		@SuppressWarnings("unchecked")		
+		Map<Integer, Integer> result = (Map<Integer, Integer>) conversionService.convert(map, sourceType, targetType);
+		assertFalse(map.equals(result));
+		assertEquals((Integer) 9, result.get(1));
+		assertEquals((Integer) 37, result.get(2));		
+	}
+	
+	public Map notGenericMapSource;
+	
+	@Test
+	public void collectionMap() throws Exception {
+		Map<String, List<String>> map = new HashMap<String, List<String>>();
+		map.put("1", Arrays.asList("9", "12"));
+		map.put("2", Arrays.asList("37", "23"));
+		TypeDescriptor sourceType = TypeDescriptor.forObject(map);
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("collectionMapTarget"));
+		assertFalse(conversionService.canConvert(sourceType, targetType));
+		conversionService.addConverter(new CollectionToCollectionConverter(conversionService));
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		@SuppressWarnings("unchecked")		
+		Map<Integer, List<Integer>> result = (Map<Integer, List<Integer>>) conversionService.convert(map, sourceType, targetType);
+		assertFalse(map.equals(result));
+		assertEquals(Arrays.asList(9, 12), result.get(1));
+		assertEquals(Arrays.asList(37, 23), result.get(2));
+	}
+
+	public Map<Integer, List<Integer>> collectionMapTarget;
+
+	@Test
+	public void collectionMapSourceTarget() throws Exception {
+		Map<String, List<String>> map = new HashMap<String, List<String>>();
+		map.put("1", Arrays.asList("9", "12"));
+		map.put("2", Arrays.asList("37", "23"));
+		TypeDescriptor sourceType = new TypeDescriptor(getClass().getField("sourceCollectionMapTarget"));
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("collectionMapTarget"));
+		conversionService.addConverter(new CollectionToCollectionConverter(conversionService));
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		@SuppressWarnings("unchecked")		
+		Map<Integer, List<Integer>> result = (Map<Integer, List<Integer>>) conversionService.convert(map, sourceType, targetType);
+		assertFalse(map.equals(result));
+		assertEquals(Arrays.asList(9, 12), result.get(1));
+		assertEquals(Arrays.asList(37, 23), result.get(2));
+	}
+
+	public Map<String, List<String>> sourceCollectionMapTarget;
+
+	@Test
+	public void collectionMapNotGenericTarget() throws Exception {
+		Map<String, List<String>> map = new HashMap<String, List<String>>();
+		map.put("1", Arrays.asList("9", "12"));
+		map.put("2", Arrays.asList("37", "23"));
+		assertTrue(conversionService.canConvert(Map.class, Map.class));
+		assertSame(map, conversionService.convert(map, Map.class));
+	}
+
+	@Test
+	public void collectionMapNotGenericTargetCollectionToObjectInteraction() throws Exception {
+		Map<String, List<String>> map = new HashMap<String, List<String>>();
+		map.put("1", Arrays.asList("9", "12"));
+		map.put("2", Arrays.asList("37", "23"));
+		conversionService.addConverter(new CollectionToCollectionConverter(conversionService));
+		conversionService.addConverter(new CollectionToObjectConverter(conversionService));
+		assertTrue(conversionService.canConvert(Map.class, Map.class));
+		assertSame(map, conversionService.convert(map, Map.class));
+	}
+	
+	@Test
+	public void emptyMap() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		TypeDescriptor sourceType = TypeDescriptor.forObject(map);
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("emptyMapTarget"));
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		assertSame(map, conversionService.convert(map, sourceType, targetType));
+	}
+
+	public Map<String, String> emptyMapTarget;
+
+	@Test
+	public void emptyMapNoTargetGenericInfo() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		assertTrue(conversionService.canConvert(Map.class, Map.class));
+		assertSame(map, conversionService.convert(map, Map.class));
+	}
+
+	@Test
+	public void emptyMapDifferentTargetImplType() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		TypeDescriptor sourceType = TypeDescriptor.forObject(map);
+		TypeDescriptor targetType = new TypeDescriptor(getClass().getField("emptyMapDifferentTarget"));
+		assertTrue(conversionService.canConvert(sourceType, targetType));
+		@SuppressWarnings("unchecked")
+		LinkedHashMap<String, String> result = (LinkedHashMap<String, String>) conversionService.convert(map, sourceType, targetType);
+		assertEquals(map, result);
+		assertEquals(LinkedHashMap.class, result.getClass());
+	}
+
+	public LinkedHashMap<String, String> emptyMapDifferentTarget;
+
+}