ExtendedProperties properties = new ExtendedProperties();
properties.load(Messages.class.getResourceAsStream("/jp/co/mclnet/sample/resource/messages.properties"),
                "UTF-8");
return properties.getString(key);

public class ExtendedPropertyMessageResources extends PropertyMessageResources {
    /**
     * コンストラクタはスーパークラスのコンストラクタを呼び出すだけです。
     */
    public ExtendedPropertyMessageResources(MessageResourcesFactory factory,
                                            String config) {
        super(factory, config);
    }

    public ExtendedPropertyMessageResources(MessageResourcesFactory factory,
                                            String config,
                                            boolean returnNull) {
        super(factory, config, returnNull);
    }

    /*
     * loadLocaleメソッドでPropertiesの代わりにExtendedPropertiesを使用します。
     */
    protected synchronized void loadLocale(String localeKey) {

        if (log.isTraceEnabled()) {
            log.trace("loadLocale(" + localeKey + ")");
        }
        
        // Have we already attempted to load messages for this locale?
        if (locales.get(localeKey) != null) {
            return;
        }
        
        locales.put(localeKey, localeKey);

        // Set up to load the property resource for this locale key, if we can
        String name = config.replace('.', '/');
        if (localeKey.length() > 0) {
            name += "_" + localeKey;
        }
        
        name += ".properties";
        InputStream is = null;
        ExtendedProperties props = new ExtendedProperties();

        // Load the specified property resource
        if (log.isTraceEnabled()) {
            log.trace("  Loading resource '" + name + "'");
        }
        
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        if (classLoader == null) {
            classLoader = this.getClass().getClassLoader();
        }
        
        is = classLoader.getResourceAsStream(name);
        if (is != null) {
            try {
                props.load(is, "UTF-8");
                
            } catch (IOException e) {
                log.error("loadLocale()", e);
            } finally {
                try {
                    is.close();
                } catch (IOException e) {
                    log.error("loadLocale()", e);
                }
            }
        }
        
        if (log.isTraceEnabled()) {
            log.trace("  Loading resource completed");
        }

        // Copy the corresponding values into our cache
        if (props.size() < 1) {
            return;
        }
        
        synchronized (messages) {
            Iterator names = props.keySet().iterator();
            while (names.hasNext()) {
                String key = (String) names.next();
                if (log.isTraceEnabled()) {
                    log.trace("  Saving message key '" + messageKey(localeKey, key));
                }
                messages.put(messageKey(localeKey, key), props.getProperty(key));
            }
        }
    }
}

public class ExtendedPropertyMessageResourcesFactory extends
                                                    MessageResourcesFactory {

    /*
     * ExtendedPropertyMessageResourcesのインスタンスを生成するだけです
     */
    public MessageResources createResources(String config) {
        return new ExtendedPropertyMessageResources(this,
                                                    config,
                                                    this.returnNull);
    }
}

<message-resources factory="jp.co.mclnet.struts.util.ExtendedPropertyMessageResourcesFactory"
                     parameter="ApplicationResources"/>

message.hello=こんにちは世界

<%@ taglib uri="http://jakarta.apache.org/struts/tags-bean"
           prefix="bean" %>

…

<bean:message key="message.hello"/>