Document correct behavior for AttributeConverterProvider

[chrylis]

I am attempting to write a custom AttributeConverterProvider for handling a specific type, and I intend to use it in conjunction with DefaultAttributeConverterProvider as described in the documentation. However, the Javadoc for AttributeConverterProvider#converterFor(EnhancedType) does not specify the correct behavior when my custom converter is asked about an unknown type (i.e., a built-in). The only example is the default implementation, which throws on an unknown type, and this does not seem like the correct behavior. Should I simply return null? (ChainConverterProvider suggests this.)

The Javadoc needs to cover the case for "not found".

[debora-ito]

DefaultStringConverterProvider seems to throw IllegalArgumentException.

aws-sdk-java-v2/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/converter/string/DefaultStringConverterProvider.java

Lines 150 to 156 in 71dfc2c

	public <T> StringConverter converterFor(EnhancedType<T> enhancedType) {
	@SuppressWarnings("unchecked") // We initialized correctly, so this is safe.
	StringConverter<T> converter = (StringConverter<T>) converterCache.get(enhancedType);
	if (converter == null) {
	throw new IllegalArgumentException("No string converter exists for " + enhancedType.rawClass());
	}

Would this be reasonable in your case?

[github-actions]

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[chrylis]

The default converter does throw, but the ChainConverterProvider seems to expect that it will return null, and that the exception is merely the questionably-handled undocumented last-resort provider.