Spring Framework example source code file (ResourceBundleMessageSource.java)

This example Spring Framework source code file (ResourceBundleMessageSource.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

abstractmessagesource, classloader, hashmap, locale, map, map, messageformat, messageformat, messagesource, missingresourceexception, resourcebundle, resourcebundle, string, string, text, util

The Spring Framework ResourceBundleMessageSource.java source code

/*
 * Copyright 2002-2007 the original author or authors.
 *
 * Licensed 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.springframework.context.support;

import java.text.MessageFormat;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;

/**
 * {@link org.springframework.context.MessageSource} implementation that
 * accesses resource bundles using specified basenames. This class relies
 * on the underlying JDK's {@link java.util.ResourceBundle} implementation,
 * in combination with the JDK's standard message parsing provided by
 * {@link java.text.MessageFormat}.
 *
 * <p>This MessageSource caches both the accessed ResourceBundle instances and
 * the generated MessageFormats for each message. It also implements rendering of
 * no-arg messages without MessageFormat, as supported by the AbstractMessageSource
 * base class. The caching provided by this MessageSource is significantly faster
 * than the built-in caching of the <code>java.util.ResourceBundle class.
 *
 * <p>Unfortunately, java.util.ResourceBundle caches loaded bundles
 * forever: Reloading a bundle during VM execution is <i>not possible.
 * As this MessageSource relies on ResourceBundle, it faces the same limitation.
 * Consider {@link ReloadableResourceBundleMessageSource} for an alternative
 * that is capable of refreshing the underlying bundle files.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #setBasenames
 * @see ReloadableResourceBundleMessageSource
 * @see java.util.ResourceBundle
 * @see java.text.MessageFormat
 */
public class ResourceBundleMessageSource extends AbstractMessageSource implements BeanClassLoaderAware {

	private String[] basenames = new String[0];

	private ClassLoader bundleClassLoader;

	private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

	/**
	 * Cache to hold loaded ResourceBundles.
	 * This Map is keyed with the bundle basename, which holds a Map that is
	 * keyed with the Locale and in turn holds the ResourceBundle instances.
	 * This allows for very efficient hash lookups, significantly faster
	 * than the ResourceBundle class's own cache.
	 */
	private final Map cachedResourceBundles = new HashMap();

	/**
	 * Cache to hold already generated MessageFormats.
	 * This Map is keyed with the ResourceBundle, which holds a Map that is
	 * keyed with the message code, which in turn holds a Map that is keyed
	 * with the Locale and holds the MessageFormat values. This allows for
	 * very efficient hash lookups without concatenated keys.
	 * @see #getMessageFormat
	 */
	private final Map cachedBundleMessageFormats = new HashMap();


	/**
	 * Set a single basename, following {@link java.util.ResourceBundle} conventions:
	 * essentially, a fully-qualified classpath location. If it doesn't contain a
	 * package qualifier (such as <code>org.mypackage), it will be resolved
	 * from the classpath root.
	 * <p>Messages will normally be held in the "/lib" or "/classes" directory of
	 * a web application's WAR structure. They can also be held in jar files on
	 * the class path.
	 * <p>Note that ResourceBundle names are effectively classpath locations: As a
	 * consequence, the JDK's standard ResourceBundle treats dots as package separators.
	 * This means that "test.theme" is effectively equivalent to "test/theme",
	 * just like it is for programmatic <code>java.util.ResourceBundle usage.
	 * @see #setBasenames
	 * @see java.util.ResourceBundle#getBundle(String)
	 */
	public void setBasename(String basename) {
		setBasenames(new String[] {basename});
	}

	/**
	 * Set an array of basenames, each following {@link java.util.ResourceBundle}
	 * conventions: essentially, a fully-qualified classpath location. If it
	 * doesn't contain a package qualifier (such as <code>org.mypackage),
	 * it will be resolved from the classpath root.
	 * <p>The associated resource bundles will be checked sequentially
	 * when resolving a message code. Note that message definitions in a
	 * <i>previous resource bundle will override ones in a later bundle,
	 * due to the sequential lookup.
	 * <p>Note that ResourceBundle names are effectively classpath locations: As a
	 * consequence, the JDK's standard ResourceBundle treats dots as package separators.
	 * This means that "test.theme" is effectively equivalent to "test/theme",
	 * just like it is for programmatic <code>java.util.ResourceBundle usage.
	 * @see #setBasename
	 * @see java.util.ResourceBundle#getBundle(String)
	 */
	public void setBasenames(String[] basenames)  {
		if (basenames != null) {
			this.basenames = new String[basenames.length];
			for (int i = 0; i < basenames.length; i++) {
				String basename = basenames[i];
				Assert.hasText(basename, "Basename must not be empty");
				this.basenames[i] = basename.trim();
			}
		}
		else {
			this.basenames = new String[0];
		}
	}

	/**
	 * Set the ClassLoader to load resource bundles with.
	 * <p>Default is the containing BeanFactory's
	 * {@link org.springframework.beans.factory.BeanClassLoaderAware bean ClassLoader},
	 * or the default ClassLoader determined by
	 * {@link org.springframework.util.ClassUtils#getDefaultClassLoader()}
	 * if not running within a BeanFactory.
	 */
	public void setBundleClassLoader(ClassLoader classLoader) {
		this.bundleClassLoader = classLoader;
	}

	/**
	 * Return the ClassLoader to load resource bundles with.
	 * <p>Default is the containing BeanFactory's bean ClassLoader.
	 * @see #setBundleClassLoader
	 */
	protected ClassLoader getBundleClassLoader() {
		return (this.bundleClassLoader != null ? this.bundleClassLoader : this.beanClassLoader);
	}

	public void setBeanClassLoader(ClassLoader classLoader) {
		this.beanClassLoader = (classLoader != null ? classLoader : ClassUtils.getDefaultClassLoader());
	}


	/**
	 * Resolves the given message code as key in the registered resource bundles,
	 * returning the value found in the bundle as-is (without MessageFormat parsing).
	 */
	protected String resolveCodeWithoutArguments(String code, Locale locale) {
		String result = null;
		for (int i = 0; result == null && i < this.basenames.length; i++) {
			ResourceBundle bundle = getResourceBundle(this.basenames[i], locale);
			if (bundle != null) {
				result = getStringOrNull(bundle, code);
			}
		}
		return result;
	}

	/**
	 * Resolves the given message code as key in the registered resource bundles,
	 * using a cached MessageFormat instance per message code.
	 */
	protected MessageFormat resolveCode(String code, Locale locale) {
		MessageFormat messageFormat = null;
		for (int i = 0; messageFormat == null && i < this.basenames.length; i++) {
			ResourceBundle bundle = getResourceBundle(this.basenames[i], locale);
			if (bundle != null) {
				messageFormat = getMessageFormat(bundle, code, locale);
			}
		}
		return messageFormat;
	}


	/**
	 * Return a ResourceBundle for the given basename and code,
	 * fetching already generated MessageFormats from the cache.
	 * @param basename the basename of the ResourceBundle
	 * @param locale the Locale to find the ResourceBundle for
	 * @return the resulting ResourceBundle, or <code>null if none
	 * found for the given basename and Locale
	 */
	protected ResourceBundle getResourceBundle(String basename, Locale locale) {
		synchronized (this.cachedResourceBundles) {
			Map localeMap = (Map) this.cachedResourceBundles.get(basename);
			if (localeMap != null) {
				ResourceBundle bundle = (ResourceBundle) localeMap.get(locale);
				if (bundle != null) {
					return bundle;
				}
			}
			try {
				ResourceBundle bundle = doGetBundle(basename, locale);
				if (localeMap == null) {
					localeMap = new HashMap();
					this.cachedResourceBundles.put(basename, localeMap);
				}
				localeMap.put(locale, bundle);
				return bundle;
			}
			catch (MissingResourceException ex) {
				if (logger.isWarnEnabled()) {
					logger.warn("ResourceBundle [" + basename + "] not found for MessageSource: " + ex.getMessage());
				}
				// Assume bundle not found
				// -> do NOT throw the exception to allow for checking parent message source.
				return null;
			}
		}
	}

	/**
	 * Obtain the resource bundle for the given basename and Locale.
	 * @param basename the basename to look for
	 * @param locale the Locale to look for
	 * @return the corresponding ResourceBundle
	 * @throws MissingResourceException if no matching bundle could be found
	 * @see java.util.ResourceBundle#getBundle(String, java.util.Locale, ClassLoader)
	 * @see #getBundleClassLoader()
	 */
	protected ResourceBundle doGetBundle(String basename, Locale locale) throws MissingResourceException {
		return ResourceBundle.getBundle(basename, locale, getBundleClassLoader());
	}

	/**
	 * Return a MessageFormat for the given bundle and code,
	 * fetching already generated MessageFormats from the cache.
	 * @param bundle the ResourceBundle to work on
	 * @param code the message code to retrieve
	 * @param locale the Locale to use to build the MessageFormat
	 * @return the resulting MessageFormat, or <code>null if no message
	 * defined for the given code
	 * @throws MissingResourceException if thrown by the ResourceBundle
	 */
	protected MessageFormat getMessageFormat(ResourceBundle bundle, String code, Locale locale)
			throws MissingResourceException {

		synchronized (this.cachedBundleMessageFormats) {
			Map codeMap = (Map) this.cachedBundleMessageFormats.get(bundle);
			Map localeMap = null;
			if (codeMap != null) {
				localeMap = (Map) codeMap.get(code);
				if (localeMap != null) {
					MessageFormat result = (MessageFormat) localeMap.get(locale);
					if (result != null) {
						return result;
					}
				}
			}

			String msg = getStringOrNull(bundle, code);
			if (msg != null) {
				if (codeMap == null) {
					codeMap = new HashMap();
					this.cachedBundleMessageFormats.put(bundle, codeMap);
				}
				if (localeMap == null) {
					localeMap = new HashMap();
					codeMap.put(code, localeMap);
				}
				MessageFormat result = createMessageFormat(msg, locale);
				localeMap.put(locale, result);
				return result;
			}

			return null;
		}
	}

	private String getStringOrNull(ResourceBundle bundle, String key) {
		try {
			return bundle.getString(key);
		}
		catch (MissingResourceException ex) {
			// Assume key not found
			// -> do NOT throw the exception to allow for checking parent message source.
			return null;
		}
	}


	/**
	 * Show the configuration of this MessageSource.
	 */
	public String toString() {
		return getClass().getName() + ": basenames=[" +
				StringUtils.arrayToCommaDelimitedString(this.basenames) + "]";
	}

}