documented hooks

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

@@ -17,6 +17,7 @@ package org.springframework.core.convert.support;
 
 import java.lang.reflect.Array;
 
+import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 
 class ArrayToArrayGenericConverter implements GenericConverter {
@@ -34,7 +35,10 @@ class ArrayToArrayGenericConverter implements GenericConverter {
 		TypeDescriptor sourceElementType = sourceType.getElementTypeDescriptor();
 		TypeDescriptor targetElementType = targetType.getElementTypeDescriptor();
 		Object target = Array.newInstance(targetElementType.getType(), Array.getLength(source));
-		GenericConverter converter = conversionService.getConverter(sourceElementType, targetElementType);
+		GenericConverter converter = conversionService.getConverter(sourceElementType, targetElementType);		
+		if (converter == null) {
+			throw new ConverterNotFoundException(sourceType, targetType);
+		}
 		for (int i = 0; i < Array.getLength(target); i++) {
 			Array.set(target, i, converter.convert(Array.get(source, i), sourceElementType, targetElementType));
 		}

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

@@ -19,6 +19,7 @@ import java.lang.reflect.Array;
 import java.util.Collection;
 
 import org.springframework.core.CollectionFactory;
+import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 
 class ArrayToCollectionGenericConverter implements GenericConverter {
@@ -40,6 +41,9 @@ class ArrayToCollectionGenericConverter implements GenericConverter {
 			}
 		} else {
 			GenericConverter converter = conversionService.getConverter(sourceElementType, targetElementType);
+			if (converter == null) {
+				throw new ConverterNotFoundException(sourceType, targetType);
+			}			
 			for (int i = 0; i < length; i++) {
 				collection.add(converter.convert(Array.get(source, i), sourceElementType, targetElementType));
 			}

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

@@ -17,6 +17,7 @@ package org.springframework.core.convert.support;
 
 import java.lang.reflect.Array;
 
+import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 
 class ArrayToObjectGenericConverter implements GenericConverter {
@@ -37,6 +38,9 @@ class ArrayToObjectGenericConverter implements GenericConverter {
 				return Array.get(source, 0);
 			} else {
 				GenericConverter converter = conversionService.getConverter(sourceElementType, targetType);
+				if (converter == null) {
+					throw new ConverterNotFoundException(sourceType, targetType);
+				}
 				return converter.convert(Array.get(source, 0), sourceElementType, targetType);
 			}
 		}

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

@@ -19,6 +19,7 @@ import java.lang.reflect.Array;
 import java.util.Collection;
 import java.util.Iterator;
 
+import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 
 class CollectionToArrayGenericConverter implements GenericConverter {
@@ -44,6 +45,9 @@ class CollectionToArrayGenericConverter implements GenericConverter {
 			}
 		} else {
 			GenericConverter converter = conversionService.getConverter(sourceElementType, targetElementType);
+			if (converter == null) {
+				throw new ConverterNotFoundException(sourceType, targetType);
+			}			
 			for (Iterator it = sourceCollection.iterator(); it.hasNext(); i++) {
 				Array.set(array, i, converter.convert(it.next(), sourceElementType, targetElementType));
 			}

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

@@ -18,6 +18,7 @@ package org.springframework.core.convert.support;
 import java.util.Collection;
 
 import org.springframework.core.CollectionFactory;
+import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 
 class CollectionToCollectionGenericConverter implements GenericConverter {
@@ -46,6 +47,9 @@ class CollectionToCollectionGenericConverter implements GenericConverter {
 		}
 		Collection targetCollection = CollectionFactory.createCollection(targetType.getType(), sourceCollection.size());
 		GenericConverter converter = conversionService.getConverter(sourceElementType, targetElementType);
+		if (converter == null) {
+			throw new ConverterNotFoundException(sourceType, targetType);
+		}		
 		for (Object element : sourceCollection) {
 			targetCollection.add(converter.convert(element, sourceElementType, targetElementType));
 		}

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

@@ -17,6 +17,7 @@ package org.springframework.core.convert.support;
 
 import java.util.Collection;
 
+import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 
 class CollectionToObjectGenericConverter implements GenericConverter {
@@ -37,6 +38,9 @@ class CollectionToObjectGenericConverter implements GenericConverter {
 				return sourceCollection.iterator().next();
 			} else {
 				GenericConverter converter = conversionService.getConverter(sourceElementType, targetType);
+				if (converter == null) {
+					throw new ConverterNotFoundException(sourceType, targetType);
+				}				
 				return converter.convert(sourceCollection.iterator().next(), sourceElementType, targetType);
 			}
 		}

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

@@ -57,7 +57,7 @@ public class GenericConversionService implements ConversionService, ConverterReg
 			return source;
 		}
 	};
-	
+
 	private GenericConversionService parent;
 
 	private final Map<Class, Map<Class, GenericConverter>> sourceTypeConverters = new HashMap<Class, Map<Class, GenericConverter>>();
@@ -162,6 +162,9 @@ public class GenericConversionService implements ConversionService, ConverterReg
 			return null;
 		}
 		GenericConverter converter = getConverter(sourceType, targetType);
+		if (converter == null) {
+			throw new ConverterNotFoundException(sourceType, targetType);
+		}
 		try {
 			return converter.convert(source, sourceType, targetType);
 		} catch (ConversionFailedException e) {
@@ -173,6 +176,9 @@ public class GenericConversionService implements ConversionService, ConverterReg
 
 	// subclassing hooks
 
+	/**
+	 * Hook to initialize the "generic" converters that require the full TypeDescriptor context to perform their conversion operations.
+	 */
 	protected void initGenericConverters() {
 		addGenericConverter(Object[].class, Object[].class, new ArrayToArrayGenericConverter(this));
 		addGenericConverter(Object[].class, Collection.class, new ArrayToCollectionGenericConverter(this));
@@ -185,14 +191,39 @@ public class GenericConversionService implements ConversionService, ConverterReg
 		addGenericConverter(Object.class, Collection.class, new ObjectToCollectionGenericConverter(this));
 	}
 
+	/**
+	 * Registers a GenericConverter.
+	 * @param sourceType the source type to convert from
+	 * @param targetType the target type to convert to
+	 * @param converter the generic converter.
+	 */
 	protected void addGenericConverter(Class<?> sourceType, Class<?> targetType, GenericConverter converter) {
 		getSourceMap(sourceType).put(targetType, converter);
 	}
 
+	/**
+	 * Hook method to convert a null value.
+	 * Default implementation simply returns <code>null</code>.
+	 * Subclasses may override to return a custom null objects for specific target types.
+	 * @param sourceType the sourceType
+	 * @param targetType the tagetType
+	 * @return the null object
+	 */
 	protected Object convertNull(TypeDescriptor sourceType, TypeDescriptor targetType) {
 		return null;
 	}
 
+	/**
+	 * Hook method to lookup the converter for a given sourceType/targetType pair.
+	 * First queries this ConversionService's converter map.
+	 * If no suitable Converter is found, and a {@link #setParent(GenericConversionService) parent} is set, then queries the parent.
+	 * If still no suitable Converter is found, returns a NO_OP Converter if the sourceType and targetType are assignable.
+	 * Returns <code>null</code> if this ConversionService simply cannot convert between sourceType and targetType.
+	 * Subclasses may override.
+	 * @param sourceType the source type to convert from
+	 * @param targetType the target type to convert to
+	 * @return the generic converter that will perform the conversion, or <code>null</code> if no suitable converter was found
+	 */
 	protected GenericConverter getConverter(TypeDescriptor sourceType, TypeDescriptor targetType) {
 		GenericConverter converter = findConverterByClassPair(sourceType.getObjectType(), targetType.getObjectType());
 		if (converter != null) {
@@ -204,7 +235,7 @@ public class GenericConversionService implements ConversionService, ConverterReg
 			if (sourceType.isAssignableTo(targetType)) {
 				return NO_OP_CONVERTER;
 			} else {
-				throw new ConverterNotFoundException(sourceType, targetType);
+				return null;
 			}
 		}
 	}

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

@@ -3,6 +3,7 @@ package org.springframework.core.convert.support;
 import java.util.Map;
 
 import org.springframework.core.CollectionFactory;
+import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 
 class MapToMapGenericConverter implements GenericConverter {
@@ -95,11 +96,17 @@ class MapToMapGenericConverter implements GenericConverter {
 				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;
 			}
 			if (sourceValueType != TypeDescriptor.NULL && targetValueType != TypeDescriptor.NULL && !valuesCompatible) {
 				this.valueConverter = conversionService.getConverter(sourceValueType, targetValueType);
+				if (this.valueConverter == null) {
+					throw new ConverterNotFoundException(sourceValueType, targetValueType);
+				}				
 				this.targetKeyType = targetKeyType;
 				this.targetValueType = targetValueType;
 			}

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

@@ -17,6 +17,7 @@ package org.springframework.core.convert.support;
 
 import java.lang.reflect.Array;
 
+import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 
 class ObjectToArrayGenericConverter implements GenericConverter {
@@ -34,6 +35,9 @@ class ObjectToArrayGenericConverter implements GenericConverter {
 			Array.set(target, 0, source);			
 		} else {
 			GenericConverter converter = conversionService.getConverter(sourceType, targetElementType);
+			if (converter == null) {
+				throw new ConverterNotFoundException(sourceType, targetType);
+			}		
 			Array.set(target, 0, converter.convert(source, sourceType, targetElementType));
 		}
 		return target;

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

@@ -18,6 +18,7 @@ package org.springframework.core.convert.support;
 import java.util.Collection;
 
 import org.springframework.core.CollectionFactory;
+import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 
 class ObjectToCollectionGenericConverter implements GenericConverter {
@@ -27,7 +28,7 @@ class ObjectToCollectionGenericConverter implements GenericConverter {
 	public ObjectToCollectionGenericConverter(GenericConversionService conversionService) {
 		this.conversionService = conversionService;
 	}
-	
+
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
 		Collection target = CollectionFactory.createCollection(targetType.getType(), 1);
 		TypeDescriptor targetElementType = targetType.getElementTypeDescriptor();
@@ -35,6 +36,9 @@ class ObjectToCollectionGenericConverter implements GenericConverter {
 			target.add(source);
 		} else {
 			GenericConverter converter = conversionService.getConverter(sourceType, targetElementType);
+			if (converter == null) {
+				throw new ConverterNotFoundException(sourceType, targetType);
+			}
 			target.add(converter.convert(source, sourceType, targetElementType));
 		}
 		return target;

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

@@ -19,6 +19,8 @@ package org.springframework.core.convert.support;
 import static junit.framework.Assert.assertEquals;
 import static junit.framework.Assert.assertNull;
 import static junit.framework.Assert.fail;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 import java.util.AbstractList;
 import java.util.ArrayList;
@@ -265,6 +267,27 @@ public class GenericConversionServiceTests {
 		assertEquals(new Integer(3), result[2]);
 	}
 
+	@Test
+	public void genericConverterDelegatingBackToConversionServiceConverterNotFound() {
+		try {
+			converter.convert("1", Integer[].class);
+		} catch (ConversionFailedException e) {
+			assertTrue(e.getCause() instanceof ConverterNotFoundException);
+		}
+	}
+	
+	@Test
+	public void parent() {
+		GenericConversionService parent = new GenericConversionService();
+		converter.setParent(parent);
+		assertFalse(converter.canConvert(String.class, Integer.class));
+		try {
+			converter.convert("3", Integer.class);
+		} catch (ConverterNotFoundException e) {
+			
+		}
+	}
+
 	public static enum FooEnum {
 		BAR, BAZ
 	}