added null handling, fixed bug relating to conversion of non-generic collections

org.springframework.context/src/main/java/org/springframework/ui/format/support/FormattingConversionServiceAdapter.java

@@ -81,6 +81,9 @@ public class FormattingConversionServiceAdapter extends GenericConversionService
 		}
 
 		public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+			if (source == null) {
+				return null;
+			}
 			try {
 				return this.formatter.parse((String) source, LocaleContextHolder.getLocale());
 			}

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

@@ -90,7 +90,11 @@ public class TypeDescriptor {
 	private TypeDescriptor() {
 	}
 
-	private TypeDescriptor(Class collectionType, TypeDescriptor elementType) {
+	/**
+	 * Internal constructor for a Collection TypeDescriptor.
+	 * @see #collection(Class, TypeDescriptor)
+	 */
+	private TypeDescriptor(Class<?> collectionType, TypeDescriptor elementType) {
 		this.type = collectionType;
 		this.elementType = elementType;
 	}
@@ -381,6 +385,16 @@ public class TypeDescriptor {
 		return (object == null ? NULL : valueOf(object.getClass()));
 	}
 
+	/**
+	 * Create a TypeDescriptor for a Collection type.
+	 * @param type the collection type
+	 * @param elementType the collection's element type
+	 * @return the type descriptor
+	 */
+	public static TypeDescriptor collection(Class<?> type, TypeDescriptor elementType) {
+		return new TypeDescriptor(type, elementType);
+	}
+	
 	public String toString() {
 		if (this == TypeDescriptor.NULL) {
 			return "[TypeDescriptor.NULL]";
@@ -389,8 +403,4 @@ public class TypeDescriptor {
 		}
 	}
 
-	public static TypeDescriptor collection(Class<?> type, TypeDescriptor elementType) {
-		return new TypeDescriptor(type, elementType);
-	}
-
 }

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

@@ -34,7 +34,7 @@ final class ArrayToArrayConverter implements GenericConverter {
 		this.helperConverter = new CollectionToArrayConverter(conversionService);
 	}
 
-	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {		
 		return this.helperConverter.convert(asList(source), sourceType, targetType);
 	}
 

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

@@ -40,6 +40,9 @@ final class ArrayToCollectionConverter implements GenericConverter {
 	}
 
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}		
 		int length = Array.getLength(source);
 		Collection collection = CollectionFactory.createCollection(targetType.getType(), length);
 		TypeDescriptor sourceElementType = sourceType.getElementTypeDescriptor();

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

@@ -41,6 +41,9 @@ final class CollectionToArrayConverter implements GenericConverter {
 	}
 
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}		
 		Collection sourceCollection = (Collection) source;
 		TypeDescriptor sourceElementType = sourceType.getElementTypeDescriptor();
 		if (sourceElementType == TypeDescriptor.NULL) {

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

@@ -16,12 +16,14 @@
 
 package org.springframework.core.convert.support;
 
+import static org.springframework.core.convert.support.ConversionUtils.getElementType;
+import static org.springframework.core.convert.support.ConversionUtils.invokeConverter;
+
 import java.util.Collection;
 
 import org.springframework.core.CollectionFactory;
 import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
-import static org.springframework.core.convert.support.ConversionUtils.*;
 
 /**
  * Converts from a source Collection to target Collection type.
@@ -39,17 +41,20 @@ final class CollectionToCollectionConverter implements GenericConverter {
 
 	@SuppressWarnings("unchecked")
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}
 		Collection sourceCollection = (Collection) source;
 		TypeDescriptor sourceElementType = sourceType.getElementTypeDescriptor();
 		if (sourceElementType == TypeDescriptor.NULL) {
 			sourceElementType = getElementType(sourceCollection);
 		}
 		TypeDescriptor targetElementType = targetType.getElementTypeDescriptor();
-		if (sourceElementType == TypeDescriptor.NULL || sourceElementType.isAssignableTo(targetElementType)) {
+		if (sourceElementType == TypeDescriptor.NULL || targetElementType == TypeDescriptor.NULL
+				|| sourceElementType.isAssignableTo(targetElementType)) {
 			if (sourceType.isAssignableTo(targetType)) {
 				return sourceCollection;
-			}
+			} else {
-			else {
 				Collection target = CollectionFactory.createCollection(targetType.getType(), sourceCollection.size());
 				target.addAll(sourceCollection);
 				return target;

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

@@ -39,6 +39,9 @@ final class CollectionToMapConverter implements GenericConverter {
 
 	@SuppressWarnings("unchecked")
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}		
 		Collection sourceCollection = (Collection) source;
 		TypeDescriptor sourceElementType = sourceType.getElementTypeDescriptor();
 		if (sourceElementType == TypeDescriptor.NULL) {

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

@@ -41,16 +41,17 @@ final class CollectionToObjectConverter implements GenericConverter {
 	}
 
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}
 		Collection sourceCollection = (Collection) source;
 		if (sourceCollection.size() == 0) {
 			if (targetType.typeEquals(String.class)) {
 				return "";
-			}
+			} else {
-			else {
 				return null;
 			}
-		}
+		} else {
-		else {
 			if (targetType.typeEquals(String.class)) {
 				TypeDescriptor sourceElementType = sourceType.getElementTypeDescriptor();
 				if (sourceElementType == TypeDescriptor.NULL) {
@@ -67,8 +68,7 @@ final class CollectionToObjectConverter implements GenericConverter {
 						i++;
 					}
 					return string.toString();
-				}
+				} else {
-				else {
 					GenericConverter converter = this.conversionService.getConverter(sourceElementType, targetType);
 					if (converter == null) {
 						throw new ConverterNotFoundException(sourceElementType, targetType);
@@ -85,8 +85,7 @@ final class CollectionToObjectConverter implements GenericConverter {
 					}
 					return string.toString();
 				}
-			}
+			} else {
-			else {
 				Object firstElement = sourceCollection.iterator().next();
 				TypeDescriptor sourceElementType = sourceType.getElementTypeDescriptor();
 				if (sourceElementType == TypeDescriptor.NULL && firstElement != null) {
@@ -94,8 +93,7 @@ final class CollectionToObjectConverter implements GenericConverter {
 				}
 				if (sourceElementType == TypeDescriptor.NULL || sourceElementType.isAssignableTo(targetType)) {
 					return firstElement;
-				}
+				} else {
-				else {
 					GenericConverter converter = this.conversionService.getConverter(sourceElementType, targetType);
 					if (converter == null) {
 						throw new ConverterNotFoundException(sourceElementType, targetType);

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

@@ -46,7 +46,7 @@ final class ConversionUtils {
 	
 
 	public static List asList(Object array) {
-		return new ArrayList(array);
+		return array != null ? new ArrayList(array) : null;
 	}
 	
 	private static class ArrayList extends AbstractList implements RandomAccess, java.io.Serializable {

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

@@ -1,25 +0,0 @@
-/**
- * 
- */
-package org.springframework.core.convert.support;
-
-import org.springframework.core.convert.TypeDescriptor;
-import org.springframework.core.convert.converter.ConverterFactory;
-
-/**
- * Adapts a ConverterFactory to the uniform GenericConverter interface.
- * @author Keith Donald 
- */
-@SuppressWarnings("unchecked")
-public final class ConverterFactoryGenericConverter implements GenericConverter {
-
-	private final ConverterFactory converterFactory;
-
-	public ConverterFactoryGenericConverter(ConverterFactory converterFactory) {
-		this.converterFactory = converterFactory;
-	}
-
-	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
-		return this.converterFactory.getConverter(targetType.getObjectType()).convert(source);
-	}
-}

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

@@ -1,37 +0,0 @@
-/*
- * Copyright 2002-2009 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 org.springframework.core.convert.TypeDescriptor;
-import org.springframework.core.convert.converter.Converter;
-
-/**
- * Adapts a Converter to the uniform GenericConverter interface.
- * @author Keith Donald
- */
-@SuppressWarnings("unchecked")
-public final class ConverterGenericConverter implements GenericConverter {
-
-	private final Converter converter;
-
-	public ConverterGenericConverter(Converter converter) {
-		this.converter = converter;
-	}
-
-	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
-		return this.converter.convert(source);
-	}
-}

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

@@ -16,9 +16,10 @@
 
 package org.springframework.core.convert.support;
 
+import static org.springframework.core.convert.support.ConversionUtils.invokeConverter;
+
 import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
-import static org.springframework.core.convert.support.ConversionUtils.*;
 
 /**
  * Helper for converting map entries.
@@ -35,21 +36,19 @@ class MapEntryConverter {
 	private TypeDescriptor sourceKeyType;
 
 	private TypeDescriptor sourceValueType;
-	
+
 	private TypeDescriptor targetKeyType;
-	
+
 	private TypeDescriptor targetValueType;
 
-
+	public MapEntryConverter(TypeDescriptor sourceKeyType, TypeDescriptor sourceValueType,
-	public MapEntryConverter(TypeDescriptor sourceKeyType, TypeDescriptor sourceValueType, TypeDescriptor targetKeyType,
+			TypeDescriptor targetKeyType, TypeDescriptor targetValueType, boolean keysCompatible,
-			TypeDescriptor targetValueType, boolean keysCompatible, boolean valuesCompatible,
+			boolean valuesCompatible, GenericConversionService conversionService) {
-			GenericConversionService conversionService) {
-
 		if (sourceKeyType != TypeDescriptor.NULL && targetKeyType != TypeDescriptor.NULL && !keysCompatible) {
 			this.keyConverter = conversionService.getConverter(sourceKeyType, targetKeyType);
 			if (this.keyConverter == null) {
 				throw new ConverterNotFoundException(sourceKeyType, targetKeyType);
-			}				
+			}
 			this.sourceKeyType = sourceKeyType;
 			this.targetKeyType = targetKeyType;
 		}
@@ -57,18 +56,16 @@ class MapEntryConverter {
 			this.valueConverter = conversionService.getConverter(sourceValueType, targetValueType);
 			if (this.valueConverter == null) {
 				throw new ConverterNotFoundException(sourceValueType, targetValueType);
-			}				
+			}
 			this.sourceValueType = sourceValueType;
 			this.targetValueType = targetValueType;
 		}
 	}
 
-
 	public Object convertKey(Object sourceKey) {
 		if (sourceKey != null && this.keyConverter != null) {
 			return invokeConverter(this.keyConverter, sourceKey, this.sourceKeyType, this.targetKeyType);
-		}
+		} else {
-		else {
 			return sourceKey;
 		}
 	}
@@ -76,8 +73,7 @@ class MapEntryConverter {
 	public Object convertValue(Object sourceValue) {
 		if (sourceValue != null && this.valueConverter != null) {
 			return invokeConverter(this.valueConverter, sourceValue, this.sourceValueType, this.targetValueType);
-		}
+		} else {
-		else {
 			return sourceValue;
 		}
 	}

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

@@ -38,6 +38,9 @@ final class MapToCollectionConverter implements GenericConverter {
 
 	@SuppressWarnings("unchecked")
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}
 		Map sourceMap = (Map) source;
 		TypeDescriptor sourceKeyType = sourceType.getMapKeyTypeDescriptor();
 		TypeDescriptor sourceValueType = sourceType.getMapValueTypeDescriptor();
@@ -52,7 +55,7 @@ final class MapToCollectionConverter implements GenericConverter {
 		}
 		Collection target = CollectionFactory.createCollection(targetType.getType(), sourceMap.size());
 		MapEntryConverter converter = new MapEntryConverter(sourceKeyType, sourceValueType, targetElementType,
-				targetElementType, keysCompatible, valuesCompatible, conversionService);
+				targetElementType, keysCompatible, valuesCompatible, this.conversionService);
 		if (targetElementType.getType().equals(String.class)) {
 			for (Object entry : sourceMap.entrySet()) {
 				Map.Entry mapEntry = (Map.Entry) entry;

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

@@ -37,6 +37,9 @@ final class MapToMapConverter implements GenericConverter {
 
 	@SuppressWarnings("unchecked")
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}
 		Map sourceMap = (Map) source;
 		TypeDescriptor targetKeyType = targetType.getMapKeyTypeDescriptor();
 		TypeDescriptor targetValueType = targetType.getMapValueTypeDescriptor();
@@ -98,8 +101,7 @@ final class MapToMapConverter implements GenericConverter {
 	private Map compatibleMapWithoutEntryConversion(Map source, TypeDescriptor targetType) {
 		if (targetType.getType().isAssignableFrom(source.getClass())) {
 			return source;
-		}
+		} else {
-		else {
 			Map target = CollectionFactory.createMap(targetType.getType(), source.size());
 			target.putAll(source);
 			return target;

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

@@ -37,16 +37,17 @@ final class MapToObjectConverter implements GenericConverter {
 	}
 
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}		
 		Map sourceMap = (Map) source;
 		if (sourceMap.size() == 0) {
 			if (targetType.typeEquals(String.class)) {
 				return "";
-			}
+			} else {
-			else {
 				return null;
 			}
-		}
+		} else {
-		else {
 			if (targetType.typeEquals(String.class)) {
 				TypeDescriptor sourceKeyType = sourceType.getMapKeyTypeDescriptor();
 				TypeDescriptor sourceValueType = sourceType.getMapValueTypeDescriptor();
@@ -71,10 +72,9 @@ final class MapToObjectConverter implements GenericConverter {
 						i++;
 					}
 					return string.toString();
-				}
+				} else {
-				else {
+					MapEntryConverter converter = new MapEntryConverter(sourceKeyType, sourceValueType, targetType,
-					MapEntryConverter converter = new MapEntryConverter(sourceKeyType, sourceValueType, targetType, targetType,
+							targetType, keysCompatible, valuesCompatible, this.conversionService);
-							keysCompatible, valuesCompatible, conversionService);
 					StringBuilder string = new StringBuilder();
 					int i = 0;
 					for (Object entry : sourceMap.entrySet()) {
@@ -90,8 +90,7 @@ final class MapToObjectConverter implements GenericConverter {
 					}
 					return string.toString();
 				}
-			}
+			} else {
-			else {
 				TypeDescriptor sourceValueType = sourceType.getMapValueTypeDescriptor();
 				boolean valuesCompatible = false;
 				if (sourceValueType == TypeDescriptor.NULL || sourceValueType.isAssignableTo(targetType)) {
@@ -99,10 +98,9 @@ final class MapToObjectConverter implements GenericConverter {
 				}
 				if (valuesCompatible) {
 					return sourceMap.values().iterator().next();
-				}
+				} else {
-				else {
+					MapEntryConverter converter = new MapEntryConverter(sourceValueType, sourceValueType, targetType,
-					MapEntryConverter converter = new MapEntryConverter(sourceValueType, sourceValueType, targetType, targetType,
+							targetType, true, valuesCompatible, this.conversionService);
-							true, valuesCompatible, conversionService);
 					Object value = sourceMap.values().iterator().next();
 					return converter.convertValue(value);
 				}

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

@@ -39,6 +39,9 @@ final class ObjectToArrayConverter implements GenericConverter {
 	}
 
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}		
 		TypeDescriptor targetElementType = targetType.getElementTypeDescriptor();
 		if (sourceType.typeEquals(String.class)) {
 			String string = (String) source;

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

@@ -39,7 +39,10 @@ final class ObjectToCollectionConverter implements GenericConverter {
 		this.conversionService = conversionService;
 	}
 
-	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {		
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}
 		TypeDescriptor targetElementType = targetType.getElementTypeDescriptor();
 		if (sourceType.typeEquals(String.class)) {
 			String string = (String) source;

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

@@ -30,7 +30,7 @@ import org.springframework.core.convert.TypeDescriptor;
 final class ObjectToMapConverter implements GenericConverter {
 
 	private final GenericConversionService conversionService;
-	
+
 	private final ArrayToMapConverter helperConverter;
 
 	public ObjectToMapConverter(GenericConversionService conversionService) {
@@ -40,12 +40,14 @@ final class ObjectToMapConverter implements GenericConverter {
 
 	@SuppressWarnings("unchecked")
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		if (source == null) {
+			return this.conversionService.convertNullSource(sourceType, targetType);
+		}
 		if (sourceType.typeEquals(String.class)) {
 			String string = (String) source;
 			String[] properties = string.split(" ");
 			return this.helperConverter.convert(properties, TypeDescriptor.valueOf(String[].class), targetType);
-		}
+		} else {
-		else {
 			Map target = CollectionFactory.createMap(targetType.getType(), 1);
 			TypeDescriptor targetKeyType = targetType.getMapKeyTypeDescriptor();
 			TypeDescriptor targetValueType = targetType.getMapValueTypeDescriptor();
@@ -59,10 +61,9 @@ final class ObjectToMapConverter implements GenericConverter {
 			}
 			if (keysCompatible && valuesCompatible) {
 				target.put(source, source);
-			}
+			} else {
-			else {
 				MapEntryConverter converter = new MapEntryConverter(sourceType, sourceType, targetKeyType,
-						targetValueType, keysCompatible, valuesCompatible, conversionService);
+						targetValueType, keysCompatible, valuesCompatible, this.conversionService);
 				Object key = converter.convertKey(source);
 				Object value = converter.convertValue(source);
 				target.put(key, value);

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

@@ -131,7 +131,8 @@ public class GenericConversionServiceTests {
 
 	@Test
 	public void convertArrayToArray() {
-		conversionService.addGenericConverter(Object[].class, Object[].class, new ArrayToArrayConverter(conversionService));
+		conversionService.addGenericConverter(Object[].class, Object[].class, new ArrayToArrayConverter(
+				conversionService));
 		conversionService.addConverterFactory(new StringToNumberConverterFactory());
 		Integer[] result = conversionService.convert(new String[] { "1", "2", "3" }, Integer[].class);
 		assertEquals(new Integer(1), result[0]);
@@ -255,12 +256,33 @@ public class GenericConversionServiceTests {
 		foo.add("1");
 		foo.add("2");
 		foo.add("3");
-		List<Integer> bar = (List<Integer>) conversionService.convert(foo, TypeDescriptor.valueOf(List.class),
+		List<Integer> bar = (List<Integer>) conversionService.convert(foo, TypeDescriptor.valueOf(LinkedHashSet.class),
 				new TypeDescriptor(getClass().getField("genericList")));
 		assertEquals(new Integer(1), bar.get(0));
 		assertEquals(new Integer(2), bar.get(1));
 		assertEquals(new Integer(3), bar.get(2));
 	}
+	
+	@Test
+	public void convertCollectionToCollectionNull() throws Exception {
+		List<Integer> bar = (List<Integer>) conversionService.convert(null, TypeDescriptor.valueOf(LinkedHashSet.class),
+				new TypeDescriptor(getClass().getField("genericList")));
+		assertNull(bar);
+	}
+
+	@Test
+	public void convertCollectionToCollectionNotGeneric() throws Exception {
+		conversionService.addConverterFactory(new StringToNumberConverterFactory());
+		Set<String> foo = new LinkedHashSet<String>();
+		foo.add("1");
+		foo.add("2");
+		foo.add("3");
+		List bar = (List) conversionService.convert(foo, TypeDescriptor.valueOf(LinkedHashSet.class), TypeDescriptor
+				.valueOf(List.class));
+		assertEquals("1", bar.get(0));
+		assertEquals("2", bar.get(1));
+		assertEquals("3", bar.get(2));
+	}
 
 	@Test
 	public void convertCollectionToString() {