NestedStringResourceLoader.java

package org.apache.wicket.examples.compref;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.wicket.Component;
import org.apache.wicket.resource.loader.IStringResourceLoader;

public class NestedStringResourceLoader implements IStringResourceLoader
{
	private static final Pattern PLACEHOLDER_PATTERN = Pattern.compile("\\{\\{([^ ]*?)\\}\\}");
	
	private List<IStringResourceLoader> loaders;

	public NestedStringResourceLoader(List<IStringResourceLoader> loaders)
	{
		this.loaders = new ArrayList<>(loaders);
	}

	@Override
	public String loadStringResource(Component component, String key, Locale locale, String style,
		String variation)
	{
		
		Iterator<IStringResourceLoader> iter = loaders.iterator();
		String value = null;
		while (iter.hasNext() && (value == null))
		{
			IStringResourceLoader loader = iter.next();
			value = loader.loadStringResource(component, key, locale, style, variation);
		}
		
		if (value != null) {
			StringBuffer output = new StringBuffer();

			Matcher matcher = PLACEHOLDER_PATTERN.matcher(value);
			// Search for other nested keys to replace
			while (matcher.find())
			{
				String replacedPlaceHolder = loadStringResource(component, matcher.group(1), locale, style, variation);
				matcher.appendReplacement(output, replacedPlaceHolder);
			}
			matcher.appendTail(output);
			
			value = output.toString();
		}
		
		return value;
	}

	@Override
	public String loadStringResource(Class<?> clazz, String key, Locale locale, String style,
		String variation)
	{
		Iterator<IStringResourceLoader> iter = loaders.iterator();
		String value = null;
		while (iter.hasNext() && (value == null))
		{
			IStringResourceLoader loader = iter.next();
			value = loader.loadStringResource(clazz, key, locale, style, variation);
		}
		
		if (value != null) {
			StringBuffer output = new StringBuffer();

			Matcher matcher = PLACEHOLDER_PATTERN.matcher(value);
			// Search for other nested keys to replace
			while (matcher.find())
			{
				String replacedPlaceHolder = loadStringResource(clazz, key, locale, style, variation);
				matcher.appendReplacement(output, replacedPlaceHolder);
			}
			matcher.appendTail(output);
			
			value = output.toString();
		}
		
		return value;
	}

}