StringToEnumConverterFactory class from enum value

Update StringToEnumConverterFactory to search superclasses until
Class.isEnum() returns true. This allows conversion when the
enum class is obtained from the enum value:

    public static enum SubFoo {
        BAR { String s() { return "x"; } };
        abstract String s();
    }

    conversionService.convert("BAR", SubFoo.BAR.getClass())

This fix is particularly important when converting collections of
enums.

Issue: SPR-10329

spring-core/src/main/java/org/springframework/core/convert/support/StringToEnumConverterFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -18,6 +18,7 @@ package org.springframework.core.convert.support;
 
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.core.convert.converter.ConverterFactory;
+import org.springframework.util.Assert;
 
 /**
  * Converts from a String to a java.lang.Enum by calling {@link Enum#valueOf(Class, String)}.
@@ -29,7 +30,13 @@ import org.springframework.core.convert.converter.ConverterFactory;
 final class StringToEnumConverterFactory implements ConverterFactory<String, Enum> {
 
 	public <T extends Enum> Converter<String, T> getConverter(Class<T> targetType) {
-		return new StringToEnum(targetType);
+		Class<?> enumType = targetType;
+		while(enumType != null && !enumType.isEnum()) {
+			enumType = enumType.getSuperclass();
+		}
+		Assert.notNull(enumType, "The target type " + targetType.getName()
+				+ " does not refer to an enum");
+		return new StringToEnum(enumType);
 	}
 
 	private class StringToEnum<T extends Enum> implements Converter<String, T> {