Java tutorial
/* * 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 * * https://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.context.ApplicationContext; import org.springframework.core.Ordered; import org.springframework.lang.Nullable; import org.springframework.web.context.support.WebApplicationObjectSupport; import org.springframework.web.servlet.View; import org.springframework.web.servlet.ViewResolver; /** * A simple implementation of {@link org.springframework.web.servlet.ViewResolver} * that interprets a view name as a bean name in the current application context, * i.e. typically in the XML file of the executing {@code DispatcherServlet}. * * <p>This resolver can be handy for small applications, keeping all definitions * ranging from controllers to views in the same place. For larger applications, * {@link XmlViewResolver} will be the better choice, as it separates the XML * view bean definitions into a dedicated views file. * * <p>Note: Neither this {@code ViewResolver} nor {@link XmlViewResolver} supports * internationalization. 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 XmlViewResolver * @see ResourceBundleViewResolver * @see UrlBasedViewResolver */ public class BeanNameViewResolver extends WebApplicationObjectSupport implements ViewResolver, Ordered { private int order = Ordered.LOWEST_PRECEDENCE; // default: same as non-Ordered /** * 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; } @Override @Nullable public View resolveViewName(String viewName, Locale locale) throws BeansException { ApplicationContext context = obtainApplicationContext(); if (!context.containsBean(viewName)) { // Allow for ViewResolver chaining... return null; } if (!context.isTypeMatch(viewName, View.class)) { if (logger.isDebugEnabled()) { logger.debug("Found bean named '" + viewName + "' but it does not implement View"); } // Since we're looking into the general ApplicationContext here, // let's accept this as a non-match and allow for chaining as well... return null; } return context.getBean(viewName, View.class); } }