restored original ConversionService behavior with respect to empty collections/maps (SPR-7728)

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 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.
@@ -58,9 +58,6 @@ final class CollectionToCollectionConverter implements ConditionalGenericConvert
 			return null;
 		}
 		Collection<?> sourceCollection = (Collection<?>) source;
-		if (sourceCollection.isEmpty()) {
-			return sourceCollection;
-		}
 		Collection target = CollectionFactory.createCollection(targetType.getType(), sourceCollection.size());
 		for (Object sourceElement : sourceCollection) {
 			Object targetElement = this.conversionService.convert(sourceElement,

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 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.
@@ -59,9 +59,6 @@ final class MapToMapConverter implements ConditionalGenericConverter {
 			return null;
 		}
 		Map<?, ?> sourceMap = (Map<?, ?>) source;
-		if (sourceMap.isEmpty()) {
-			return sourceMap;
-		}
 		Map targetMap = CollectionFactory.createMap(targetType.getType(), sourceMap.size());
 		for (Object entry : sourceMap.entrySet()) {
 			Map.Entry sourceMapEntry = (Map.Entry) entry;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 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.
@@ -24,18 +24,19 @@ import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 
-import static org.junit.Assert.*;
 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.convert.converter.Converter;
-import org.springframework.core.io.Resource;
 import org.springframework.core.io.DescriptiveResource;
+import org.springframework.core.io.Resource;
 import org.springframework.util.StopWatch;
 import org.springframework.util.StringUtils;
 
+import static org.junit.Assert.*;
+
 /**
  * @author Keith Donald
  * @author Juergen Hoeller
@@ -271,9 +272,7 @@ public class GenericConversionServiceTests {
 		GenericConversionService service = ConversionServiceFactory.createDefaultConversionService();
 		List list = Collections.emptyList();
 		List result = service.convert(list, List.class);
-		assertSame(list, result);
-		result = service.convert(list, list.getClass());
-		assertSame(list, result);
+		assertTrue(result.isEmpty());
 	}
 
 	@Test
@@ -281,9 +280,7 @@ public class GenericConversionServiceTests {
 		GenericConversionService service = ConversionServiceFactory.createDefaultConversionService();
 		Map map = Collections.emptyMap();
 		Map result = service.convert(map, Map.class);
-		assertSame(map, result);
-		result = service.convert(map, map.getClass());
-		assertSame(map, result);
+		assertTrue(result.isEmpty());
 	}
 
 	@Test