wicket/src/main/java/org/apache/wicket/Localizer.java - wicket - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
  * The ASF licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package org.apache.wicket;

 import java.util.Iterator;
 import java.util.Locale;
 import java.util.Map;
 import java.util.MissingResourceException;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.atomic.AtomicLong;

 import org.apache.wicket.markup.repeater.AbstractRepeater;
 import org.apache.wicket.model.IModel;
 import org.apache.wicket.resource.loader.IStringResourceLoader;
 import org.apache.wicket.settings.IResourceSettings;
 import org.apache.wicket.util.string.AppendingStringBuffer;
 import org.apache.wicket.util.string.interpolator.PropertyVariableInterpolator;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;


 /**
  * A utility class that encapsulates all of the localization related functionality in a way that it
  * can be accessed by all areas of the framework in a consistent way. A singleton instance of this
  * class is available via the <code>Application</code> object.
  * <p>
  * You may register additional IStringResourceLoader to extend or replace Wickets default search
  * strategy for the properties. E.g. string resource loaders which load the properties from a
  * database. There should be no need to extend Localizer.
  *
  * @see org.apache.wicket.settings.Settings#getLocalizer()
  * @see org.apache.wicket.resource.loader.IStringResourceLoader
  * @see org.apache.wicket.settings.Settings#getStringResourceLoaders()
  *
  * @author Chris Turner
  * @author Juergen Donnerstag
  */
 public class Localizer
 {
 	private static final Logger log = LoggerFactory.getLogger(Localizer.class);

 	/** ConcurrentHashMap does not allow null values */
 	private static final String NULL_VALUE = "<null-value>";

 	/** Cache properties */
 	private Map<String, String> cache = newCache();

 	/** */
 	private final ClassMetaDatabase metaDatabase = new ClassMetaDatabase();

 	/**
 	 * Create the utils instance class backed by the configuration information contained within the
 	 * supplied application object.
 	 */
 	public Localizer()
 	{
 	}

 	/**
 	 * Clear all cache entries
 	 */
 	public final void clearCache()
 	{
 		if (cache != null)
 		{
 			cache = newCache();
 		}
 	}

 	/**
 	 * @see #getString(String, Component, IModel, Locale, String, String)
 	 *
 	 * @param key
 	 *            The key to obtain the resource for
 	 * @param component
 	 *            The component to get the resource for
 	 * @return The string resource
 	 * @throws MissingResourceException
 	 *             If resource not found and configuration dictates that exception should be thrown
 	 */
 	public String getString(final String key, final Component component)
 		throws MissingResourceException
 	{
 		return getString(key, component, null, null);
 	}

 	/**
 	 * @see #getString(String, Component, IModel, Locale, String, String)
 	 *
 	 * @param key
 	 *            The key to obtain the resource for
 	 * @param component
 	 *            The component to get the resource for
 	 * @param model
 	 *            The model to use for property substitutions in the strings (optional)
 	 * @return The string resource
 	 * @throws MissingResourceException
 	 *             If resource not found and configuration dictates that exception should be thrown
 	 */
 	public String getString(final String key, final Component component, final IModel<?> model)
 		throws MissingResourceException
 	{
 		return getString(key, component, model, null);
 	}

 	/**
 	 * @see #getString(String, Component, IModel, Locale, String, String)
 	 *
 	 * @param key
 	 *            The key to obtain the resource for
 	 * @param component
 	 *            The component to get the resource for
 	 * @param defaultValue
 	 *            The default value (optional)
 	 * @return The string resource
 	 * @throws MissingResourceException
 	 *             If resource not found and configuration dictates that exception should be thrown
 	 */
 	public String getString(final String key, final Component component, final String defaultValue)
 		throws MissingResourceException
 	{
 		return getString(key, component, null, defaultValue);
 	}

 	/**
 	 * This method is now deprecated.
 	 *
 	 * @param key
 	 * @param component
 	 * @param model
 	 * @param locale
 	 * @param style
 	 * @param defaultValue
 	 * @return String
 	 * @throws MissingResourceException
 	 *
 	 * @Deprecated please use {@link #getString(String, Component, IModel, String)}
 	 */
 	public String getString(final String key, final Component component, final IModel<?> model,
 		final Locale locale, final String style, final String defaultValue)
 		throws MissingResourceException
 	{
 		return getString(key, component, model, defaultValue);
 	}

 	/**
 	 * This is similar to {@link #getString(String, Component, IModel, String)} except that the
 	 * resource settings are ignored. This allows to to code something like
 	 *
 	 * <pre>
 	 * String option = getLocalizer().getStringIgnoreSettings(getId() + &quot;.null&quot;, this, &quot;&quot;);
 	 * if (Strings.isEmpty(option))
 	 * {
 	 * 	option = getLocalizer().getString(&quot;null&quot;, this, CHOOSE_ONE);
 	 * }
 	 * </pre>
 	 *
 	 * @param key
 	 *            The key to obtain the resource for
 	 * @param component
 	 *            The component to get the resource for (optional)
 	 * @param model
 	 *            The model to use for substitutions in the strings (optional)
 	 * @param defaultValue
 	 *            The default value (optional)
 	 * @return The string resource
 	 */
 	public String getStringIgnoreSettings(final String key, final Component component,
 		final IModel<?> model, final String defaultValue)
 	{
 		boolean addedToPage = false;
 		if (component != null)
 		{
 			if ((component instanceof Page) || null != component.findParent(Page.class))
 			{
 				addedToPage = true;
 			}

 			if (!addedToPage)
 			{
 				log.warn(
 					"Tried to retrieve a localized string for a component that has not yet been added to the page. "
 						+ "This can sometimes lead to an invalid or no localized resource returned. "
 						+ "Make sure you are not calling Component#getString() inside your Component's constructor. "
 						+ "Offending component: {}", component);
 			}
 		}

 		String cacheKey = null;
 		String value = null;

 		// If this component is not yet added to page we do not want to check
 		// cache as we can generate an invalid cache key
 		if ((cache != null) && addedToPage)
 		{
 			cacheKey = getCacheKey(key, component);
 		}

 		// Value not found are cached as well (value = null)
 		if ((cacheKey != null) && cache.containsKey(cacheKey))
 		{
 			value = getFromCache(cacheKey);
 			if (log.isDebugEnabled())
 			{
 				log.debug("Property found in cache: '" + key + "'; Component: '" +
 					(component != null ? component.toString(false) : null) + "'; value: '" + value +
 					"'");
 			}
 		}
 		else
 		{
 			if (log.isDebugEnabled())
 			{
 				log.debug("Locate property: key: '" + key + "'; Component: '" +
 					(component != null ? component.toString(false) : null) + "'");
 			}

 			// Iterate over all registered string resource loaders until the
 			// property has been found
 			Iterator<IStringResourceLoader> iter = getStringResourceLoaders();
 			while (iter.hasNext())
 			{
 				IStringResourceLoader loader = iter.next();
 				value = loader.loadStringResource(component, key);
 				if (value != null)
 				{
 					break;
 				}
 			}

 			// Cache the result incl null if not found
 			if (cacheKey != null)
 			{
 				putIntoCache(cacheKey, value);
 			}

 			if ((value == null) && log.isDebugEnabled())
 			{
 				log.debug("Property not found; key: '" + key + "'; Component: '" +
 					(component != null ? component.toString(false) : null) + "'");
 			}
 		}

 		if (value == null)
 		{
 			value = defaultValue;
 		}

 		// If a property value has been found, or a default value was given,
 		// than replace the placeholder and we are done
 		if (value != null)
 		{
 			return substitutePropertyExpressions(component, value, model);
 		}

 		return null;
 	}

 	/**
 	 * In case you want to provide your own list of string resource loaders
 	 *
 	 * @return Iterator
 	 */
 	protected Iterator<IStringResourceLoader> getStringResourceLoaders()
 	{
 		Iterator<IStringResourceLoader> iter = Application.get()
 			.getResourceSettings()
 			.getStringResourceLoaders()
 			.iterator();
 		return iter;
 	}

 	/**
 	 * Get the localized string using all of the supplied parameters. This method is left public to
 	 * allow developers full control over string resource loading. However, it is recommended that
 	 * one of the other convenience methods in the class are used as they handle all of the work
 	 * related to obtaining the current user locale and style information.
 	 *
 	 * @param key
 	 *            The key to obtain the resource for
 	 * @param component
 	 *            The component to get the resource for (optional)
 	 * @param model
 	 *            The model to use for substitutions in the strings (optional)
 	 * @param defaultValue
 	 *            The default value (optional)
 	 * @return The string resource
 	 * @throws MissingResourceException
 	 *             If resource not found and configuration dictates that exception should be thrown
 	 */
 	public String getString(final String key, final Component component, final IModel<?> model,
 		final String defaultValue) throws MissingResourceException
 	{
 		final IResourceSettings resourceSettings = Application.get().getResourceSettings();

 		String value = getStringIgnoreSettings(key, component, model, null);
 		if ((value == null) && (defaultValue != null))
 		{
 			// Resource not found, so handle missing resources based on
 			// application configuration and try the default value
 			if (resourceSettings.getUseDefaultOnMissingResource())
 			{
 				value = defaultValue;
 			}
 		}

 		// If a property value has been found, or a default value was given,
 		// than replace the placeholder and we are done
 		if (value != null)
 		{
 			return substitutePropertyExpressions(component, value, model);
 		}

 		if (resourceSettings.getThrowExceptionOnMissingResource())
 		{
 			AppendingStringBuffer message = new AppendingStringBuffer("Unable to find property: '");
 			message.append(key);
 			message.append("'");

 			if (component != null)
 			{
 				message.append(" for component: ");
 				message.append(component.getPageRelativePath());
 				message.append(" [class=").append(component.getClass().getName()).append("]");
 			}

 			throw new MissingResourceException(message.toString(), (component != null
 				? component.getClass().getName() : ""), key);
 		}

 		return "[Warning: Property for '" + key + "' not found]";
 	}

 	/**
 	 * Put the value into the cache and associate it with the cache key
 	 *
 	 * @param cacheKey
 	 * @param string
 	 */
 	protected void putIntoCache(final String cacheKey, final String string)
 	{
 		if (cache == null)
 		{
 			return;
 		}

 		// ConcurrentHashMap does not allow null values
 		if (string == null)
 		{
 			cache.put(cacheKey, NULL_VALUE);
 		}
 		else
 		{
 			cache.put(cacheKey, string);
 		}
 	}

 	/**
 	 * Get the value associated with the key from the cache.
 	 *
 	 * @param cacheKey
 	 * @return The value of the key
 	 */
 	protected String getFromCache(final String cacheKey)
 	{
 		if (cache == null)
 		{
 			return null;
 		}

 		final String value = cache.get(cacheKey);

 		// ConcurrentHashMap does not allow null values
 		if (value == NULL_VALUE)
 		{
 			return null;
 		}
 		return value;
 	}

 	/**
 	 * Gets the cache key
 	 *
 	 * @param key
 	 * @param component
 	 * @return The value of the key
 	 */
 	protected String getCacheKey(final String key, final Component component)
 	{
 		String cacheKey = key;
 		if (component != null)
 		{
 			AppendingStringBuffer buffer = new AppendingStringBuffer(200);
 			buffer.append(key);

 			Component cursor = component;
 			while (cursor != null)
 			{
 				buffer.append("-").append(metaDatabase.id(cursor.getClass()));

 				if (cursor instanceof Page)
 				{
 					break;
 				}

 				if (cursor.getParent() != null && !(cursor.getParent() instanceof AbstractRepeater))
 				{
 					/*
 					 * only append component id if parent is not a repeater because
 					 *
 					 * (a) these ids are irrelevant when generating resource cache keys
 					 *
 					 * (b) they cause a lot of redundant keys to be generated
 					 */
 					buffer.append(":").append(cursor.getId());
 				}
 				cursor = cursor.getParent();

 			}

 			buffer.append("-").append(component.getLocale());
 			buffer.append("-").append(component.getStyle());
 			// TODO 1.4 look if we want to properly separate getstyle/getvariation
 			// for now getvariation() is rolled up into getstyle()
 			// buffer.append("-").append(component.getVariation());
 			cacheKey = buffer.toString();
 		}
 		return cacheKey;
 	}

 	/**
 	 * Helper method to handle property variable substitution in strings.
 	 *
 	 * @param component
 	 *            The component requesting a model value
 	 * @param string
 	 *            The string to substitute into
 	 * @param model
 	 *            The model
 	 * @return The resulting string
 	 */
 	public String substitutePropertyExpressions(final Component component, final String string,
 		final IModel<?> model)
 	{
 		if ((string != null) && (model != null))
 		{
 			return PropertyVariableInterpolator.interpolate(string, model.getObject());
 		}
 		return string;
 	}

 	/**
 	 * By default the cache is enabled. Disabling the cache will disable it and clear the cache.
 	 * This can be handy for example in development mode.
 	 *
 	 * @param value
 	 */
 	public final void setEnableCache(boolean value)
 	{
 		if (value == false)
 		{
 			cache = null;
 		}
 		else if (cache == null)
 		{
 			cache = newCache();
 		}
 	}

 	/**
 	 * Create a new cache, override this method if you want a different map to store the cache keys,
 	 * for example a map that hold only the last X number of elements..
 	 *
 	 * By default it uses the {@link ConcurrentHashMap}
 	 *
 	 * @return cache
 	 */
 	protected Map<String, String> newCache()
 	{
 		return new ConcurrentHashMap<String, String>();
 	}

 	/**
 	 * Database that maps class names to an integer id. This is used to make localizer keys shorter
 	 * because sometimes they can contain a large number of class names.
 	 *
 	 * @author igor.vaynberg
 	 */
 	private static class ClassMetaDatabase
 	{
 		private final ConcurrentMap<String, Long> nameToId = new ConcurrentHashMap<String, Long>();
 		private final AtomicLong nameCounter = new AtomicLong();

 		/**
 		 * Returns a unique id that represents this class' name. This can be used for compressing
 		 * class names. Notice this id should not be used across cluster nodes.
 		 *
 		 * @param clazz
 		 * @return long id of class name
 		 */
 		public long id(Class<?> clazz)
 		{
 			final String name = clazz.getName();
 			Long id = nameToId.get(name);
 			if (id == null)
 			{
 				id = nameCounter.incrementAndGet();
 				Long previousId = nameToId.putIfAbsent(name, id);
 				if (previousId != null)
 				{
 					id = previousId;
 				}
 			}
 			return id;
 		}
 	}


 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one or more
	* contributor license agreements. See the NOTICE file distributed with
	* this work for additional information regarding copyright ownership.
	* The ASF licenses this file to You under the Apache License, Version 2.0
	* (the "License"); you may not use this file except in compliance with
	* the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package org.apache.wicket;

	import java.util.Iterator;
	import java.util.Locale;
	import java.util.Map;
	import java.util.MissingResourceException;
	import java.util.concurrent.ConcurrentHashMap;
	import java.util.concurrent.ConcurrentMap;
	import java.util.concurrent.atomic.AtomicLong;

	import org.apache.wicket.markup.repeater.AbstractRepeater;
	import org.apache.wicket.model.IModel;
	import org.apache.wicket.resource.loader.IStringResourceLoader;
	import org.apache.wicket.settings.IResourceSettings;
	import org.apache.wicket.util.string.AppendingStringBuffer;
	import org.apache.wicket.util.string.interpolator.PropertyVariableInterpolator;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;


	/**
	* A utility class that encapsulates all of the localization related functionality in a way that it
	* can be accessed by all areas of the framework in a consistent way. A singleton instance of this
	* class is available via the <code>Application</code> object.
	* <p>
	* You may register additional IStringResourceLoader to extend or replace Wickets default search
	* strategy for the properties. E.g. string resource loaders which load the properties from a
	* database. There should be no need to extend Localizer.
	*
	* @see org.apache.wicket.settings.Settings#getLocalizer()
	* @see org.apache.wicket.resource.loader.IStringResourceLoader
	* @see org.apache.wicket.settings.Settings#getStringResourceLoaders()
	*
	* @author Chris Turner
	* @author Juergen Donnerstag
	*/
	public class Localizer
	{
	private static final Logger log = LoggerFactory.getLogger(Localizer.class);

	/** ConcurrentHashMap does not allow null values */
	private static final String NULL_VALUE = "<null-value>";

	/** Cache properties */
	private Map<String, String> cache = newCache();

	/** */
	private final ClassMetaDatabase metaDatabase = new ClassMetaDatabase();

	/**
	* Create the utils instance class backed by the configuration information contained within the
	* supplied application object.
	*/
	public Localizer()
	{
	}

	/**
	* Clear all cache entries
	*/
	public final void clearCache()
	{
	if (cache != null)
	{
	cache = newCache();
	}
	}

	/**
	* @see #getString(String, Component, IModel, Locale, String, String)
	*
	* @param key
	* The key to obtain the resource for
	* @param component
	* The component to get the resource for
	* @return The string resource
	* @throws MissingResourceException
	* If resource not found and configuration dictates that exception should be thrown
	*/
	public String getString(final String key, final Component component)
	throws MissingResourceException
	{
	return getString(key, component, null, null);
	}

	/**
	* @see #getString(String, Component, IModel, Locale, String, String)
	*
	* @param key
	* The key to obtain the resource for
	* @param component
	* The component to get the resource for
	* @param model
	* The model to use for property substitutions in the strings (optional)
	* @return The string resource
	* @throws MissingResourceException
	* If resource not found and configuration dictates that exception should be thrown
	*/
	public String getString(final String key, final Component component, final IModel<?> model)
	throws MissingResourceException
	{
	return getString(key, component, model, null);
	}

	/**
	* @see #getString(String, Component, IModel, Locale, String, String)
	*
	* @param key
	* The key to obtain the resource for
	* @param component
	* The component to get the resource for
	* @param defaultValue
	* The default value (optional)
	* @return The string resource
	* @throws MissingResourceException
	* If resource not found and configuration dictates that exception should be thrown
	*/
	public String getString(final String key, final Component component, final String defaultValue)
	throws MissingResourceException
	{
	return getString(key, component, null, defaultValue);
	}

	/**
	* This method is now deprecated.
	*
	* @param key
	* @param component
	* @param model
	* @param locale
	* @param style
	* @param defaultValue
	* @return String
	* @throws MissingResourceException
	*
	* @Deprecated please use {@link #getString(String, Component, IModel, String)}
	*/
	public String getString(final String key, final Component component, final IModel<?> model,
	final Locale locale, final String style, final String defaultValue)
	throws MissingResourceException
	{
	return getString(key, component, model, defaultValue);
	}

	/**
	* This is similar to {@link #getString(String, Component, IModel, String)} except that the
	* resource settings are ignored. This allows to to code something like
	*
	* <pre>
	* String option = getLocalizer().getStringIgnoreSettings(getId() + ".null", this, "");
	* if (Strings.isEmpty(option))
	* {
	* option = getLocalizer().getString("null", this, CHOOSE_ONE);
	* }
	* </pre>
	*
	* @param key
	* The key to obtain the resource for
	* @param component
	* The component to get the resource for (optional)
	* @param model
	* The model to use for substitutions in the strings (optional)
	* @param defaultValue
	* The default value (optional)
	* @return The string resource
	*/
	public String getStringIgnoreSettings(final String key, final Component component,
	final IModel<?> model, final String defaultValue)
	{
	boolean addedToPage = false;
	if (component != null)
	{
	if ((component instanceof Page) \|\| null != component.findParent(Page.class))
	{
	addedToPage = true;
	}

	if (!addedToPage)
	{
	log.warn(
	"Tried to retrieve a localized string for a component that has not yet been added to the page. "
	+ "This can sometimes lead to an invalid or no localized resource returned. "
	+ "Make sure you are not calling Component#getString() inside your Component's constructor. "
	+ "Offending component: {}", component);
	}
	}

	String cacheKey = null;
	String value = null;

	// If this component is not yet added to page we do not want to check
	// cache as we can generate an invalid cache key
	if ((cache != null) && addedToPage)
	{
	cacheKey = getCacheKey(key, component);
	}

	// Value not found are cached as well (value = null)
	if ((cacheKey != null) && cache.containsKey(cacheKey))
	{
	value = getFromCache(cacheKey);
	if (log.isDebugEnabled())
	{
	log.debug("Property found in cache: '" + key + "'; Component: '" +
	(component != null ? component.toString(false) : null) + "'; value: '" + value +
	"'");
	}
	}
	else
	{
	if (log.isDebugEnabled())
	{
	log.debug("Locate property: key: '" + key + "'; Component: '" +
	(component != null ? component.toString(false) : null) + "'");
	}

	// Iterate over all registered string resource loaders until the
	// property has been found
	Iterator<IStringResourceLoader> iter = getStringResourceLoaders();
	while (iter.hasNext())
	{
	IStringResourceLoader loader = iter.next();
	value = loader.loadStringResource(component, key);
	if (value != null)
	{
	break;
	}
	}

	// Cache the result incl null if not found
	if (cacheKey != null)
	{
	putIntoCache(cacheKey, value);
	}

	if ((value == null) && log.isDebugEnabled())
	{
	log.debug("Property not found; key: '" + key + "'; Component: '" +
	(component != null ? component.toString(false) : null) + "'");
	}
	}

	if (value == null)
	{
	value = defaultValue;
	}

	// If a property value has been found, or a default value was given,
	// than replace the placeholder and we are done
	if (value != null)
	{
	return substitutePropertyExpressions(component, value, model);
	}

	return null;
	}

	/**
	* In case you want to provide your own list of string resource loaders
	*
	* @return Iterator
	*/
	protected Iterator<IStringResourceLoader> getStringResourceLoaders()
	{
	Iterator<IStringResourceLoader> iter = Application.get()
	.getResourceSettings()
	.getStringResourceLoaders()
	.iterator();
	return iter;
	}

	/**
	* Get the localized string using all of the supplied parameters. This method is left public to
	* allow developers full control over string resource loading. However, it is recommended that
	* one of the other convenience methods in the class are used as they handle all of the work
	* related to obtaining the current user locale and style information.
	*
	* @param key
	* The key to obtain the resource for
	* @param component
	* The component to get the resource for (optional)
	* @param model
	* The model to use for substitutions in the strings (optional)
	* @param defaultValue
	* The default value (optional)
	* @return The string resource
	* @throws MissingResourceException
	* If resource not found and configuration dictates that exception should be thrown
	*/
	public String getString(final String key, final Component component, final IModel<?> model,
	final String defaultValue) throws MissingResourceException
	{
	final IResourceSettings resourceSettings = Application.get().getResourceSettings();

	String value = getStringIgnoreSettings(key, component, model, null);
	if ((value == null) && (defaultValue != null))
	{
	// Resource not found, so handle missing resources based on
	// application configuration and try the default value
	if (resourceSettings.getUseDefaultOnMissingResource())
	{
	value = defaultValue;
	}
	}

	// If a property value has been found, or a default value was given,
	// than replace the placeholder and we are done
	if (value != null)
	{
	return substitutePropertyExpressions(component, value, model);
	}

	if (resourceSettings.getThrowExceptionOnMissingResource())
	{
	AppendingStringBuffer message = new AppendingStringBuffer("Unable to find property: '");
	message.append(key);
	message.append("'");

	if (component != null)
	{
	message.append(" for component: ");
	message.append(component.getPageRelativePath());
	message.append(" [class=").append(component.getClass().getName()).append("]");
	}

	throw new MissingResourceException(message.toString(), (component != null
	? component.getClass().getName() : ""), key);
	}

	return "[Warning: Property for '" + key + "' not found]";
	}

	/**
	* Put the value into the cache and associate it with the cache key
	*
	* @param cacheKey
	* @param string
	*/
	protected void putIntoCache(final String cacheKey, final String string)
	{
	if (cache == null)
	{
	return;
	}

	// ConcurrentHashMap does not allow null values
	if (string == null)
	{
	cache.put(cacheKey, NULL_VALUE);
	}
	else
	{
	cache.put(cacheKey, string);
	}
	}

	/**
	* Get the value associated with the key from the cache.
	*
	* @param cacheKey
	* @return The value of the key
	*/
	protected String getFromCache(final String cacheKey)
	{
	if (cache == null)
	{
	return null;
	}

	final String value = cache.get(cacheKey);

	// ConcurrentHashMap does not allow null values
	if (value == NULL_VALUE)
	{
	return null;
	}
	return value;
	}

	/**
	* Gets the cache key
	*
	* @param key
	* @param component
	* @return The value of the key
	*/
	protected String getCacheKey(final String key, final Component component)
	{
	String cacheKey = key;
	if (component != null)
	{
	AppendingStringBuffer buffer = new AppendingStringBuffer(200);
	buffer.append(key);

	Component cursor = component;
	while (cursor != null)
	{
	buffer.append("-").append(metaDatabase.id(cursor.getClass()));

	if (cursor instanceof Page)
	{
	break;
	}

	if (cursor.getParent() != null && !(cursor.getParent() instanceof AbstractRepeater))
	{
	/*
	* only append component id if parent is not a repeater because
	*
	* (a) these ids are irrelevant when generating resource cache keys
	*
	* (b) they cause a lot of redundant keys to be generated
	*/
	buffer.append(":").append(cursor.getId());
	}
	cursor = cursor.getParent();

	}

	buffer.append("-").append(component.getLocale());
	buffer.append("-").append(component.getStyle());
	// TODO 1.4 look if we want to properly separate getstyle/getvariation
	// for now getvariation() is rolled up into getstyle()
	// buffer.append("-").append(component.getVariation());
	cacheKey = buffer.toString();
	}
	return cacheKey;
	}

	/**
	* Helper method to handle property variable substitution in strings.
	*
	* @param component
	* The component requesting a model value
	* @param string
	* The string to substitute into
	* @param model
	* The model
	* @return The resulting string
	*/
	public String substitutePropertyExpressions(final Component component, final String string,
	final IModel<?> model)
	{
	if ((string != null) && (model != null))
	{
	return PropertyVariableInterpolator.interpolate(string, model.getObject());
	}
	return string;
	}

	/**
	* By default the cache is enabled. Disabling the cache will disable it and clear the cache.
	* This can be handy for example in development mode.
	*
	* @param value
	*/
	public final void setEnableCache(boolean value)
	{
	if (value == false)
	{
	cache = null;
	}
	else if (cache == null)
	{
	cache = newCache();
	}
	}

	/**
	* Create a new cache, override this method if you want a different map to store the cache keys,
	* for example a map that hold only the last X number of elements..
	*
	* By default it uses the {@link ConcurrentHashMap}
	*
	* @return cache
	*/
	protected Map<String, String> newCache()
	{
	return new ConcurrentHashMap<String, String>();
	}

	/**
	* Database that maps class names to an integer id. This is used to make localizer keys shorter
	* because sometimes they can contain a large number of class names.
	*
	* @author igor.vaynberg
	*/
	private static class ClassMetaDatabase
	{
	private final ConcurrentMap<String, Long> nameToId = new ConcurrentHashMap<String, Long>();
	private final AtomicLong nameCounter = new AtomicLong();

	/**
	* Returns a unique id that represents this class' name. This can be used for compressing
	* class names. Notice this id should not be used across cluster nodes.
	*
	* @param clazz
	* @return long id of class name
	*/
	public long id(Class<?> clazz)
	{
	final String name = clazz.getName();
	Long id = nameToId.get(name);
	if (id == null)
	{
	id = nameCounter.incrementAndGet();
	Long previousId = nameToId.putIfAbsent(name, id);
	if (previousId != null)
	{
	id = previousId;
	}
	}
	return id;
	}
	}


	}