added utility method to reduce code duplication

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

@@ -49,23 +49,7 @@ final class ArrayToCollectionConverter implements ConditionalGenericConverter {
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		if (targetType.getElementTypeDescriptor() == null) {
+		return ConversionUtils.canConvertElements(sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(), conversionService);
-			// yes
-			return true;
-		}
-		boolean canConvert = conversionService.canConvert(sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor());
-		if (canConvert) {
-			// yes
-			return true;
-		} else {
-			if (sourceType.getElementTypeDescriptor().getType().isAssignableFrom(targetType.getElementTypeDescriptor().getType())) {
-				// maybe;
-				return true;
-			} else {
-				// no;
-				return false;
-			}
-		}
 	}
 
 	@SuppressWarnings("unchecked")

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

@@ -49,23 +49,7 @@ final class CollectionToArrayConverter implements ConditionalGenericConverter {
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		if (sourceType.getElementTypeDescriptor() == null) {
+		return ConversionUtils.canConvertElements(sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(), conversionService);
-			// maybe
-			return true;
-		}
-		boolean canConvert = conversionService.canConvert(sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor());
-		if (canConvert) {
-			// yes
-			return true;
-		} else {
-			if (sourceType.getElementTypeDescriptor().getType().isAssignableFrom(targetType.getElementTypeDescriptor().getType())) {
-				// maybe;
-				return true;
-			} else {
-				// no;
-				return false;
-			}
-		}
 	}
 
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {

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

@@ -49,27 +49,7 @@ final class CollectionToCollectionConverter implements ConditionalGenericConvert
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		if (targetType.getElementTypeDescriptor() == null) {
+		return ConversionUtils.canConvertElements(sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor(), conversionService);
-			// yes
-			return true;
-		}
-		if (sourceType.getElementTypeDescriptor() == null) {
-			// maybe
-			return true;
-		}
-		boolean canConvert = conversionService.canConvert(sourceType.getElementTypeDescriptor(), targetType.getElementTypeDescriptor());
-		if (canConvert) {
-			// yes
-			return true;
-		} else {
-			if (sourceType.getElementTypeDescriptor().getType().isAssignableFrom(targetType.getElementTypeDescriptor().getType())) {
-				// maybe;
-				return true;
-			} else {
-				// no;
-				return false;
-			}
-		}
 	}
 
 	@SuppressWarnings("unchecked")

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

@@ -43,23 +43,7 @@ final class CollectionToObjectConverter implements ConditionalGenericConverter {
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		if (sourceType.getElementTypeDescriptor() == null) {
+		return ConversionUtils.canConvertElements(sourceType.getElementTypeDescriptor(), targetType, conversionService);
-			// maybe
-			return true;
-		}
-		boolean canConvert = conversionService.canConvert(sourceType.getElementTypeDescriptor(), targetType);
-		if (canConvert) {
-			// yes
-			return true;
-		} else {
-			if (sourceType.getElementTypeDescriptor().getType().isAssignableFrom(targetType.getType())) {
-				// maybe;
-				return true;
-			} else {
-				// no;
-				return false;
-			}
-		}
 	}
 
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {

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

@@ -45,23 +45,7 @@ final class CollectionToStringConverter implements ConditionalGenericConverter {
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		if (sourceType.getElementTypeDescriptor() == null) {
+		return ConversionUtils.canConvertElements(sourceType.getElementTypeDescriptor(), targetType, conversionService);
-			// maybe
-			return true;
-		}
-		boolean canConvert = conversionService.canConvert(sourceType.getElementTypeDescriptor(), targetType);
-		if (canConvert) {
-			// yes
-			return true;
-		} else {
-			if (sourceType.getElementTypeDescriptor().getType().isAssignableFrom(targetType.getType())) {
-				// maybe;
-				return true;
-			} else {
-				// no;
-				return false;
-			}
-		}
 	}
 
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {

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

@@ -17,6 +17,7 @@
 package org.springframework.core.convert.support;
 
 import org.springframework.core.convert.ConversionFailedException;
+import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.converter.GenericConverter;
 
@@ -40,5 +41,29 @@ abstract class ConversionUtils {
 			throw new ConversionFailedException(sourceType, targetType, source, ex);
 		}
 	}
+	
+	public static boolean canConvertElements(TypeDescriptor sourceElementType, TypeDescriptor targetElementType, ConversionService conversionService) {
+		if (targetElementType == null) {
+			// yes
+			return true;
+		}
+		if (sourceElementType == null) {
+			// maybe
+			return true;
+		}
+		boolean canConvert = conversionService.canConvert(sourceElementType, targetElementType);
+		if (canConvert) {
+			// yes
+			return true;
+		} else {
+			if (sourceElementType.getType().isAssignableFrom(targetElementType.getType())) {
+				// maybe;
+				return true;
+			} else {
+				// no;
+				return false;
+			}
+		}		
+	}
 
 }

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

@@ -72,51 +72,11 @@ final class MapToMapConverter implements ConditionalGenericConverter {
 	// internal helpers
 
 	private boolean canConvertKey(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		if (targetType.getMapKeyTypeDescriptor() == null) {
+		return ConversionUtils.canConvertElements(sourceType.getMapKeyTypeDescriptor(), targetType.getMapKeyTypeDescriptor(), conversionService);
-			// yes
-			return true;
-		}
-		if (sourceType.getMapKeyTypeDescriptor() == null) {
-			// maybe
-			return true;
-		}
-		boolean canConvert = conversionService.canConvert(sourceType.getMapKeyTypeDescriptor(), targetType.getMapKeyTypeDescriptor());
-		if (canConvert) {
-			// yes
-			return true;
-		} else {
-			if (sourceType.getMapKeyTypeDescriptor().getType().isAssignableFrom(targetType.getMapKeyTypeDescriptor().getType())) {
-				// maybe;
-				return true;
-			} else {
-				// no;
-				return false;
-			}
-		}
 	}
 	
 	private boolean canConvertValue(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		if (targetType.getMapValueTypeDescriptor() == null) {
+		return ConversionUtils.canConvertElements(sourceType.getMapValueTypeDescriptor(), targetType.getMapValueTypeDescriptor(), conversionService);
-			// yes
-			return true;
-		}
-		if (sourceType.getMapValueTypeDescriptor() == null) {
-			// maybe
-			return true;
-		}
-		boolean canConvert = conversionService.canConvert(sourceType.getMapValueTypeDescriptor(), targetType.getMapValueTypeDescriptor());
-		if (canConvert) {
-			// yes
-			return true;
-		} else {
-			if (sourceType.getMapValueTypeDescriptor().getType().isAssignableFrom(targetType.getMapValueTypeDescriptor().getType())) {
-				// maybe;
-				return true;
-			} else {
-				// no;
-				return false;
-			}
-		}
 	}
 	
 	private Object convertKey(Object sourceKey, TypeDescriptor sourceType, TypeDescriptor targetType) {

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

@@ -44,19 +44,7 @@ final class ObjectToArrayConverter implements ConditionalGenericConverter {
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		boolean canConvert = conversionService.canConvert(sourceType, targetType.getElementTypeDescriptor());
+		return ConversionUtils.canConvertElements(sourceType, targetType.getElementTypeDescriptor(), conversionService);
-		if (canConvert) {
-			// yes
-			return true;
-		} else {
-			if (sourceType.getType().isAssignableFrom(targetType.getElementTypeDescriptor().getType())) {
-				// maybe;
-				return true;
-			} else {
-				// no;
-				return false;
-			}
-		}
 	}
 
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {

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

@@ -46,23 +46,7 @@ final class ObjectToCollectionConverter implements ConditionalGenericConverter {
 	}
 
 	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
-		if (targetType.getElementTypeDescriptor() == null) {
+		return ConversionUtils.canConvertElements(sourceType, targetType.getElementTypeDescriptor(), conversionService);
-			// yes
-			return true;
-		}		
-		boolean canConvert = conversionService.canConvert(sourceType, targetType.getElementTypeDescriptor());
-		if (canConvert) {
-			// yes
-			return true;
-		} else {
-			if (sourceType.getType().isAssignableFrom(targetType.getElementTypeDescriptor().getType())) {
-				// maybe;
-				return true;
-			} else {
-				// no;
-				return false;
-			}
-		}
 	}
 
 	@SuppressWarnings("unchecked")