/*
    * Copyright 2002-2012 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.Locale;
  
  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.xml.ResourceEntityResolver;
  import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
  import org.springframework.context.ConfigurableApplicationContext;
  import org.springframework.core.Ordered;
  import org.springframework.core.io.Resource;
  import org.springframework.web.context.support.GenericWebApplicationContext;
  import org.springframework.web.servlet.View;
  
  /**
   * A {@link org.springframework.web.servlet.ViewResolver} implementation that uses
   * bean definitions in a dedicated XML file for view definitions, specified by
   * resource location. The file will typically be located in the WEB-INF directory;
   * the default is "/WEB-INF/views.xml".
   *
   * <p>This {@code ViewResolver} does not support internationalization at the level
   * of its definition resources. Consider {@link ResourceBundleViewResolver} if you
   * need to apply different view resources per locale.
   *
   * <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 Juergen Hoeller
   * @since 18.06.2003
   * @see org.springframework.context.ApplicationContext#getResource
   * @see ResourceBundleViewResolver
   * @see UrlBasedViewResolver
   */
  public class XmlViewResolver extends AbstractCachingViewResolver
  		implements Ordered, InitializingBean, DisposableBean {
  
  	/** Default if no other location is supplied */
  	public final static String DEFAULT_LOCATION = "/WEB-INF/views.xml";
  
  
  	private int order = Integer.MAX_VALUE;  // default: same as non-Ordered
  
  	private Resource location;
  
  	private ConfigurableApplicationContext cachedFactory;
  
  
  	public void setOrder(int order) {
  		this.order = order;
  	}
  
  	@Override
  	public int getOrder() {
  		return this.order;
  	}
  
  	/**
  	 * Set the location of the XML file that defines the view beans.
  	 * <p>The default is "/WEB-INF/views.xml".
  	 * @param location the location of the XML file.
  	 */
  	public void setLocation(Resource location) {
  		this.location = location;
  	}
  
  	/**
  	 * Pre-initialize the factory from the XML file.
  	 * Only effective if caching is enabled.
  	 */
  	@Override
  	public void afterPropertiesSet() throws BeansException {
  		if (isCache()) {
  			initFactory();
  		}
  	}
  
  
 	/**
 	 * This implementation returns just the view name,
 	 * as XmlViewResolver doesn't support localized resolution.
 	 */
 	@Override
 	protected Object getCacheKey(String viewName, Locale locale) {
 		return viewName;
 	}
 
 	@Override
 	protected View loadView(String viewName, Locale locale) throws BeansException {
 		BeanFactory factory = initFactory();
 		try {
 			return factory.getBean(viewName, View.class);
 		}
 		catch (NoSuchBeanDefinitionException ex) {
 			// Allow for ViewResolver chaining...
 			return null;
 		}
 	}
 
 	/**
 	 * Initialize the view bean factory from the XML file.
 	 * Synchronized because of access by parallel threads.
 	 * @throws BeansException in case of initialization errors
 	 */
 	protected synchronized BeanFactory initFactory() throws BeansException {
 		if (this.cachedFactory != null) {
 			return this.cachedFactory;
 		}
 
 		Resource actualLocation = this.location;
 		if (actualLocation == null) {
 			actualLocation = getApplicationContext().getResource(DEFAULT_LOCATION);
 		}
 
 		// Create child ApplicationContext for views.
 		GenericWebApplicationContext factory = new GenericWebApplicationContext();
 		factory.setParent(getApplicationContext());
 		factory.setServletContext(getServletContext());
 
 		// Load XML resource with context-aware entity resolver.
 		XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
 		reader.setEnvironment(getApplicationContext().getEnvironment());
 		reader.setEntityResolver(new ResourceEntityResolver(getApplicationContext()));
 		reader.loadBeanDefinitions(actualLocation);
 
 		factory.refresh();
 
 		if (isCache()) {
 			this.cachedFactory = factory;
 		}
 		return factory;
 	}
 
 
 	/**
 	 * Close the view bean factory on context shutdown.
 	 */
 	@Override
 	public void destroy() throws BeansException {
 		if (this.cachedFactory != null) {
 			this.cachedFactory.close();
 		}
 	}
 
 }