001/*
002 * Copyright 2002-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.servlet.view;
018
019import java.util.Locale;
020
021import org.springframework.beans.BeansException;
022import org.springframework.beans.factory.BeanFactory;
023import org.springframework.beans.factory.DisposableBean;
024import org.springframework.beans.factory.InitializingBean;
025import org.springframework.beans.factory.NoSuchBeanDefinitionException;
026import org.springframework.beans.factory.xml.ResourceEntityResolver;
027import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
028import org.springframework.context.ConfigurableApplicationContext;
029import org.springframework.core.Ordered;
030import org.springframework.core.io.Resource;
031import org.springframework.web.context.support.GenericWebApplicationContext;
032import org.springframework.web.servlet.View;
033
034/**
035 * A {@link org.springframework.web.servlet.ViewResolver} implementation that uses
036 * bean definitions in a dedicated XML file for view definitions, specified by
037 * resource location. The file will typically be located in the WEB-INF directory;
038 * the default is "/WEB-INF/views.xml".
039 *
040 * <p>This {@code ViewResolver} does not support internationalization at the level
041 * of its definition resources. Consider {@link ResourceBundleViewResolver} if you
042 * need to apply different view resources per locale.
043 *
044 * <p>Note: This {@code ViewResolver} implements the {@link Ordered} interface
045 * in order to allow for flexible participation in {@code ViewResolver} chaining.
046 * For example, some special views could be defined via this {@code ViewResolver}
047 * (giving it 0 as "order" value), while all remaining views could be resolved by
048 * a {@link UrlBasedViewResolver}.
049 *
050 * @author Juergen Hoeller
051 * @since 18.06.2003
052 * @see org.springframework.context.ApplicationContext#getResource
053 * @see ResourceBundleViewResolver
054 * @see UrlBasedViewResolver
055 */
056public class XmlViewResolver extends AbstractCachingViewResolver
057                implements Ordered, InitializingBean, DisposableBean {
058
059        /** Default if no other location is supplied */
060        public static final String DEFAULT_LOCATION = "/WEB-INF/views.xml";
061
062
063        private Resource location;
064
065        private ConfigurableApplicationContext cachedFactory;
066
067        private int order = Ordered.LOWEST_PRECEDENCE;  // default: same as non-Ordered
068
069
070        /**
071         * Set the location of the XML file that defines the view beans.
072         * <p>The default is "/WEB-INF/views.xml".
073         * @param location the location of the XML file.
074         */
075        public void setLocation(Resource location) {
076                this.location = location;
077        }
078
079        /**
080         * Specify the order value for this ViewResolver bean.
081         * <p>The default value is {@code Ordered.LOWEST_PRECEDENCE}, meaning non-ordered.
082         * @see org.springframework.core.Ordered#getOrder()
083         */
084        public void setOrder(int order) {
085                this.order = order;
086        }
087
088        @Override
089        public int getOrder() {
090                return this.order;
091        }
092
093        /**
094         * Pre-initialize the factory from the XML file.
095         * Only effective if caching is enabled.
096         */
097        @Override
098        public void afterPropertiesSet() throws BeansException {
099                if (isCache()) {
100                        initFactory();
101                }
102        }
103
104
105        /**
106         * This implementation returns just the view name,
107         * as XmlViewResolver doesn't support localized resolution.
108         */
109        @Override
110        protected Object getCacheKey(String viewName, Locale locale) {
111                return viewName;
112        }
113
114        @Override
115        protected View loadView(String viewName, Locale locale) throws BeansException {
116                BeanFactory factory = initFactory();
117                try {
118                        return factory.getBean(viewName, View.class);
119                }
120                catch (NoSuchBeanDefinitionException ex) {
121                        // Allow for ViewResolver chaining...
122                        return null;
123                }
124        }
125
126        /**
127         * Initialize the view bean factory from the XML file.
128         * Synchronized because of access by parallel threads.
129         * @throws BeansException in case of initialization errors
130         */
131        protected synchronized BeanFactory initFactory() throws BeansException {
132                if (this.cachedFactory != null) {
133                        return this.cachedFactory;
134                }
135
136                Resource actualLocation = this.location;
137                if (actualLocation == null) {
138                        actualLocation = getApplicationContext().getResource(DEFAULT_LOCATION);
139                }
140
141                // Create child ApplicationContext for views.
142                GenericWebApplicationContext factory = new GenericWebApplicationContext();
143                factory.setParent(getApplicationContext());
144                factory.setServletContext(getServletContext());
145
146                // Load XML resource with context-aware entity resolver.
147                XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
148                reader.setEnvironment(getApplicationContext().getEnvironment());
149                reader.setEntityResolver(new ResourceEntityResolver(getApplicationContext()));
150                reader.loadBeanDefinitions(actualLocation);
151
152                factory.refresh();
153
154                if (isCache()) {
155                        this.cachedFactory = factory;
156                }
157                return factory;
158        }
159
160
161        /**
162         * Close the view bean factory on context shutdown.
163         */
164        @Override
165        public void destroy() throws BeansException {
166                if (this.cachedFactory != null) {
167                        this.cachedFactory.close();
168                }
169        }
170
171}