https://github.com/spring-projects/spring-framework: Spring Web MVC (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2018 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.web.servlet.view;

import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.beans.factory.support.PropertiesBeanDefinitionReader;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.Ordered;
import org.springframework.lang.Nullable;
import org.springframework.web.context.support.GenericWebApplicationContext;
import org.springframework.web.servlet.View;


A ViewResolver implementation that uses bean definitions in a ResourceBundle, specified by the bundle basename. 
The bundle is typically defined in a properties file, located in the classpath.
The default bundle basename is "views".

This ViewResolver supports localized view definitions, using the default support of PropertyResourceBundle. For example, the basename "views" will be resolved as class path resources "views_de_AT.properties", "views_de.properties", "views.properties" - for a given Locale "de_AT". 
Note: This ViewResolver implements the Ordered interface in order to allow for flexible participation in ViewResolver chaining. For example, some special views could be defined via this ViewResolver (giving it 0 as "order" value), while all remaining views could be resolved by a UrlBasedViewResolver. 
Author:Rod Johnson, Juergen Hoeller
See Also:
/**
 * A {@link org.springframework.web.servlet.ViewResolver} implementation that uses
 * bean definitions in a {@link ResourceBundle}, specified by the bundle basename.
 *
 * <p>The bundle is typically defined in a properties file, located in the classpath.
 * The default bundle basename is "views".
 *
 * <p>This {@code ViewResolver} supports localized view definitions, using the
 * default support of {@link java.util.PropertyResourceBundle}. For example, the
 * basename "views" will be resolved as class path resources "views_de_AT.properties",
 * "views_de.properties", "views.properties" - for a given Locale "de_AT".
 *
 * <p>Note: This {@code ViewResolver} implements the {@link Ordered} interface
 * in order to allow for flexible participation in {@code ViewResolver} chaining.
 * For example, some special views could be defined via this {@code ViewResolver}
 * (giving it 0 as "order" value), while all remaining views could be resolved by
 * a {@link UrlBasedViewResolver}.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see java.util.ResourceBundle#getBundle
 * @see java.util.PropertyResourceBundle
 * @see UrlBasedViewResolver
 */
public class ResourceBundleViewResolver extends AbstractCachingViewResolver
		implements Ordered, InitializingBean, DisposableBean {

	
The default basename if no other basename is supplied. 
/** The default basename if no other basename is supplied. */
	public static final String DEFAULT_BASENAME = "views";


	private String[] basenames = new String[] {DEFAULT_BASENAME};

	private ClassLoader bundleClassLoader = Thread.currentThread().getContextClassLoader();

	@Nullable
	private String defaultParentView;

	@Nullable
	private Locale[] localesToInitialize;

	private int order = Ordered.LOWEST_PRECEDENCE;  // default: same as non-Ordered

	/* Locale -> BeanFactory */
	private final Map<Locale, BeanFactory> localeCache = new HashMap<>();

	/* List of ResourceBundle -> BeanFactory */
	private final Map<List<ResourceBundle>, ConfigurableApplicationContext> bundleCache = new HashMap<>();


	
Set a single basename, following ResourceBundle conventions. The default is "views". 
ResourceBundle supports different locale suffixes. For example, a base name of "views" might map to ResourceBundle files "views", "views_en_au" and "views_de". 
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 java.util.ResourceBundle usage. 
See Also:
/**
	 * Set a single basename, following {@link java.util.ResourceBundle} conventions.
	 * The default is "views".
	 * <p>{@code ResourceBundle} supports different locale suffixes. For example,
	 * a base name of "views" might map to {@code ResourceBundle} files
	 * "views", "views_en_au" and "views_de".
	 * <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 ResourceBundle#getBundle(String)
	 * @see ResourceBundle#getBundle(String, Locale)
	 */
	public void setBasename(String basename) {
		setBasenames(basename);
	}

	
Set an array of basenames, each following ResourceBundle conventions. The default is a single basename "views". 
ResourceBundle supports different locale suffixes. For example, a base name of "views" might map to ResourceBundle files "views", "views_en_au" and "views_de". 
The associated resource bundles will be checked sequentially when resolving
a message code. Note that message definitions in a previous resource
bundle will override ones in a later bundle, due to the sequential lookup.

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 java.util.ResourceBundle usage. 
See Also:
/**
	 * Set an array of basenames, each following {@link java.util.ResourceBundle}
	 * conventions. The default is a single basename "views".
	 * <p>{@code ResourceBundle} supports different locale suffixes. For example,
	 * a base name of "views" might map to {@code ResourceBundle} files
	 * "views", "views_en_au" and "views_de".
	 * <p>The associated resource bundles will be checked sequentially when resolving
	 * a message code. Note that message definitions in a <i>previous</i> 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 ResourceBundle#getBundle(String)
	 * @see ResourceBundle#getBundle(String, Locale)
	 */
	public void setBasenames(String... basenames) {
		this.basenames = basenames;
	}

	
Set the ClassLoader to load resource bundles with. Default is the thread context ClassLoader. 
/**
	 * Set the {@link ClassLoader} to load resource bundles with.
	 * Default is the thread context {@code ClassLoader}.
	 */
	public void setBundleClassLoader(ClassLoader classLoader) {
		this.bundleClassLoader = classLoader;
	}

	
Return the ClassLoader to load resource bundles with. 
Default is the specified bundle ClassLoader, usually the thread context ClassLoader. 
/**
	 * Return the {@link ClassLoader} to load resource bundles with.
	 * <p>Default is the specified bundle {@code ClassLoader},
	 * usually the thread context {@code ClassLoader}.
	 */
	protected ClassLoader getBundleClassLoader() {
		return this.bundleClassLoader;
	}

	
Set the default parent for views defined in the ResourceBundle. 
This avoids repeated "yyy1.(parent)=xxx", "yyy2.(parent)=xxx" definitions
in the bundle, especially if all defined views share the same parent.

The parent will typically define the view class and common attributes.
Concrete views might simply consist of an URL definition then:
a la "yyy1.url=/my.jsp", "yyy2.url=/your.jsp".

View definitions that define their own parent or carry their own
class can still override this. Strictly speaking, the rule that a
default parent setting does not apply to a bean definition that
carries a class is there for backwards compatibility reasons.
It still matches the typical use case.

/**
	 * Set the default parent for views defined in the {@code ResourceBundle}.
	 * <p>This avoids repeated "yyy1.(parent)=xxx", "yyy2.(parent)=xxx" definitions
	 * in the bundle, especially if all defined views share the same parent.
	 * <p>The parent will typically define the view class and common attributes.
	 * Concrete views might simply consist of an URL definition then:
	 * a la "yyy1.url=/my.jsp", "yyy2.url=/your.jsp".
	 * <p>View definitions that define their own parent or carry their own
	 * class can still override this. Strictly speaking, the rule that a
	 * default parent setting does not apply to a bean definition that
	 * carries a class is there for backwards compatibility reasons.
	 * It still matches the typical use case.
	 */
	public void setDefaultParentView(String defaultParentView) {
		this.defaultParentView = defaultParentView;
	}

	
Specify Locales to initialize eagerly, rather than lazily when actually accessed.

Allows for pre-initialization of common Locales, eagerly checking
the view configuration for those Locales.

/**
	 * Specify Locales to initialize eagerly, rather than lazily when actually accessed.
	 * <p>Allows for pre-initialization of common Locales, eagerly checking
	 * the view configuration for those Locales.
	 */
	public void setLocalesToInitialize(Locale... localesToInitialize) {
		this.localesToInitialize = localesToInitialize;
	}

	
Specify the order value for this ViewResolver bean.

The default value is Ordered.LOWEST_PRECEDENCE, meaning non-ordered. 
See Also:
/**
	 * Specify the order value for this ViewResolver bean.
	 * <p>The default value is {@code Ordered.LOWEST_PRECEDENCE}, meaning non-ordered.
	 * @see org.springframework.core.Ordered#getOrder()
	 */
	public void setOrder(int order) {
		this.order = order;
	}

	@Override
	public int getOrder() {
		return this.order;
	}

	
Eagerly initialize Locales if necessary.

See Also:
  • setLocalesToInitialize
/**
	 * Eagerly initialize Locales if necessary.
	 * @see #setLocalesToInitialize
	 */
	@Override
	public void afterPropertiesSet() throws BeansException {
		if (this.localesToInitialize != null) {
			for (Locale locale : this.localesToInitialize) {
				initFactory(locale);
			}
		}
	}


	@Override
	protected View loadView(String viewName, Locale locale) throws Exception {
		BeanFactory factory = initFactory(locale);
		try {
			return factory.getBean(viewName, View.class);
		}
		catch (NoSuchBeanDefinitionException ex) {
			// Allow for ViewResolver chaining...
			return null;
		}
	}

	
Initialize the View BeanFactory from the ResourceBundle, for the given locale. 
Synchronized because of access by parallel threads.

Params:
  • locale – the target Locale
Throws:
Returns:the View factory for the given Locale
/**
	 * Initialize the View {@link BeanFactory} from the {@code ResourceBundle},
	 * for the given {@link Locale locale}.
	 * <p>Synchronized because of access by parallel threads.
	 * @param locale the target {@code Locale}
	 * @return the View factory for the given Locale
	 * @throws BeansException in case of initialization errors
	 */
	protected synchronized BeanFactory initFactory(Locale locale) throws BeansException {
		// Try to find cached factory for Locale:
		// Have we already encountered that Locale before?
		if (isCache()) {
			BeanFactory cachedFactory = this.localeCache.get(locale);
			if (cachedFactory != null) {
				return cachedFactory;
			}
		}

		// Build list of ResourceBundle references for Locale.
		List<ResourceBundle> bundles = new LinkedList<>();
		for (String basename : this.basenames) {
			ResourceBundle bundle = getBundle(basename, locale);
			bundles.add(bundle);
		}

		// Try to find cached factory for ResourceBundle list:
		// even if Locale was different, same bundles might have been found.
		if (isCache()) {
			BeanFactory cachedFactory = this.bundleCache.get(bundles);
			if (cachedFactory != null) {
				this.localeCache.put(locale, cachedFactory);
				return cachedFactory;
			}
		}

		// Create child ApplicationContext for views.
		GenericWebApplicationContext factory = new GenericWebApplicationContext();
		factory.setParent(getApplicationContext());
		factory.setServletContext(getServletContext());

		// Load bean definitions from resource bundle.
		PropertiesBeanDefinitionReader reader = new PropertiesBeanDefinitionReader(factory);
		reader.setDefaultParentBean(this.defaultParentView);
		for (ResourceBundle bundle : bundles) {
			reader.registerBeanDefinitions(bundle);
		}

		factory.refresh();

		// Cache factory for both Locale and ResourceBundle list.
		if (isCache()) {
			this.localeCache.put(locale, factory);
			this.bundleCache.put(bundles, factory);
		}

		return factory;
	}

	
Obtain the resource bundle for the given basename and Locale. 
Params:
  • basename – the basename to look for
  • locale – the Locale to look for
Throws:
See Also:
Returns:the corresponding ResourceBundle
/**
	 * Obtain the resource bundle for the given basename and {@link Locale}.
	 * @param basename the basename to look for
	 * @param locale the {@code Locale} to look for
	 * @return the corresponding {@code ResourceBundle}
	 * @throws MissingResourceException if no matching bundle could be found
	 * @see ResourceBundle#getBundle(String, Locale, ClassLoader)
	 */
	protected ResourceBundle getBundle(String basename, Locale locale) throws MissingResourceException {
		return ResourceBundle.getBundle(basename, locale, getBundleClassLoader());
	}


	
Close the bundle View factories on context shutdown.

/**
	 * Close the bundle View factories on context shutdown.
	 */
	@Override
	public void destroy() throws BeansException {
		for (ConfigurableApplicationContext factory : this.bundleCache.values()) {
			factory.close();
		}
		this.localeCache.clear();
		this.bundleCache.clear();
	}

}