LocaleProviderFactory.java

package net.jhorstmann.i18n;

import java.util.List;
import java.util.ServiceLoader;

import net.jhorstmann.i18n.impl.DefaultLocaleProviderFactory;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public abstract class LocaleProviderFactory {

	private static final Logger log = LoggerFactory.getLogger(LocaleProviderFactory.class);
	
    private static final LocaleProviderFactory DEFAULT_INSTANCE = new DefaultLocaleProviderFactory();

    private static List<LocaleProviderFactory> instances;

    /**
     * Loads a {@link LocaleProviderFactory} using Java's {@link java.util.ServiceLoader} infrastructure.
     * @return 
     */
    public static LocaleProviderFactory newInstance() {
        if (instances == null) {
            instances = ServiceLoaderHelper.load(LocaleProviderFactory.class.getClassLoader(), LocaleProviderFactory.class);
            log.debug("Found {} LocaleProviderFactories",instances.size());
        }
        for (LocaleProviderFactory factory : instances) {
            if (factory.isEnvironmentSupported()) {
                return factory;
            }
        }
        log.debug("no registered LocaleProviderFactory found, returning default provider-factory");
        return DEFAULT_INSTANCE;
    }

    /**
     * Return whether this {@link LocaleProviderFactory} is usable in this environment.
     * This makes it possible to configure multiple implementations in a project where
     * one is used when run as a webapp and another one for scripts and tests.
     * @return 
     */
    public abstract boolean isEnvironmentSupported();

    public abstract LocaleProvider newLocaleProvider();
}