CascadingConverter.java

package fr.openwide.core.wicket.more.util.convert.converters;

import java.util.Locale;

import org.apache.wicket.util.convert.ConversionException;
import org.apache.wicket.util.convert.IConverter;

import com.google.common.collect.ImmutableList;

public class CascadingConverter<T> implements IConverter<T> {
	
	private static final long serialVersionUID = 4943347630093315725L;
	
	private final Iterable<? extends IConverter<? extends T>> preemptiveConverters;

	private final IConverter<T> mainConverter;
	
	private final Iterable<? extends IConverter<? extends T>> alternativeConverters;

	public CascadingConverter(IConverter<T> mainConverter,
			Iterable<? extends IConverter<? extends T>> preemptiveConverters,
			Iterable<? extends IConverter<? extends T>> alternativeConverters) {
		super();
		this.preemptiveConverters = ImmutableList.copyOf(preemptiveConverters);
		this.mainConverter = mainConverter;
		this.alternativeConverters = ImmutableList.copyOf(alternativeConverters);
	}

	@Override
	public T convertToObject(String value, Locale locale) throws ConversionException {
		// First try the preemptive converters
		for (IConverter<? extends T> preemptiveConverter : preemptiveConverters) {
			try {
				return preemptiveConverter.convertToObject(value, locale);
			} catch (ConversionException ignored) {
			}
		}

		// If they didn't work, ignore the errors and try the main converter
		try {
			return mainConverter.convertToObject(value, locale);
		} catch (ConversionException e) {
			// If the main converter didn't work, try an alternative converter
			for (IConverter<? extends T> alternativeConverter : alternativeConverters) {
				try {
					return alternativeConverter.convertToObject(value, locale);
				} catch (ConversionException ignored) {
					e.addSuppressed(ignored);
				}
			}
			// If no alternative converter managed to convert, just throw the original exception.
			throw e;
		}
	}

	@Override
	public String convertToString(T value, Locale locale) {
		// Just use the main converter.
		return mainConverter.convertToString(value, locale);
	}

}