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.context.ApplicationContext;
023import org.springframework.core.Ordered;
024import org.springframework.web.context.support.WebApplicationObjectSupport;
025import org.springframework.web.servlet.View;
026import org.springframework.web.servlet.ViewResolver;
027
028/**
029 * A simple implementation of {@link org.springframework.web.servlet.ViewResolver}
030 * that interprets a view name as a bean name in the current application context,
031 * i.e. typically in the XML file of the executing {@code DispatcherServlet}.
032 *
033 * <p>This resolver can be handy for small applications, keeping all definitions
034 * ranging from controllers to views in the same place. For larger applications,
035 * {@link XmlViewResolver} will be the better choice, as it separates the XML
036 * view bean definitions into a dedicated views file.
037 *
038 * <p>Note: Neither this {@code ViewResolver} nor {@link XmlViewResolver} supports
039 * internationalization. Consider {@link ResourceBundleViewResolver} if you need
040 * to apply different view resources per locale.
041 *
042 * <p>Note: This {@code ViewResolver} implements the {@link Ordered} interface
043 * in order to allow for flexible participation in {@code ViewResolver} chaining.
044 * For example, some special views could be defined via this {@code ViewResolver}
045 * (giving it 0 as "order" value), while all remaining views could be resolved by
046 * a {@link UrlBasedViewResolver}.
047 *
048 * @author Juergen Hoeller
049 * @since 18.06.2003
050 * @see XmlViewResolver
051 * @see ResourceBundleViewResolver
052 * @see UrlBasedViewResolver
053 */
054public class BeanNameViewResolver extends WebApplicationObjectSupport implements ViewResolver, Ordered {
055
056        private int order = Ordered.LOWEST_PRECEDENCE;  // default: same as non-Ordered
057
058
059        /**
060         * Specify the order value for this ViewResolver bean.
061         * <p>The default value is {@code Ordered.LOWEST_PRECEDENCE}, meaning non-ordered.
062         * @see org.springframework.core.Ordered#getOrder()
063         */
064        public void setOrder(int order) {
065                this.order = order;
066        }
067
068        @Override
069        public int getOrder() {
070                return this.order;
071        }
072
073
074        @Override
075        public View resolveViewName(String viewName, Locale locale) throws BeansException {
076                ApplicationContext context = getApplicationContext();
077                if (!context.containsBean(viewName)) {
078                        if (logger.isDebugEnabled()) {
079                                logger.debug("No matching bean found for view name '" + viewName + "'");
080                        }
081                        // Allow for ViewResolver chaining...
082                        return null;
083                }
084                if (!context.isTypeMatch(viewName, View.class)) {
085                        if (logger.isDebugEnabled()) {
086                                logger.debug("Found matching bean for view name '" + viewName +
087                                                "' - to be ignored since it does not implement View");
088                        }
089                        // Since we're looking into the general ApplicationContext here,
090                        // let's accept this as a non-match and allow for chaining as well...
091                        return null;
092                }
093                return context.getBean(viewName, View.class);
094        }
095
096}