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.context.support; 018 019import java.util.Map; 020 021import javax.servlet.ServletContext; 022 023import org.apache.commons.logging.Log; 024import org.apache.commons.logging.LogFactory; 025 026import org.springframework.lang.Nullable; 027import org.springframework.web.context.ServletContextAware; 028 029/** 030 * Exporter that takes Spring-defined objects and exposes them as 031 * ServletContext attributes. Usually, bean references will be used 032 * to export Spring-defined beans as ServletContext attributes. 033 * 034 * <p>Useful to make Spring-defined beans available to code that is 035 * not aware of Spring at all, but rather just of the Servlet API. 036 * Client code can then use plain ServletContext attribute lookups 037 * to access those objects, despite them being defined in a Spring 038 * application context. 039 * 040 * <p>Alternatively, consider using the WebApplicationContextUtils 041 * class to access Spring-defined beans via the WebApplicationContext 042 * interface. This makes client code aware of Spring API, of course. 043 * 044 * @author Juergen Hoeller 045 * @since 1.1.4 046 * @see javax.servlet.ServletContext#getAttribute 047 * @see WebApplicationContextUtils#getWebApplicationContext 048 */ 049public class ServletContextAttributeExporter implements ServletContextAware { 050 051 protected final Log logger = LogFactory.getLog(getClass()); 052 053 @Nullable 054 private Map<String, Object> attributes; 055 056 057 /** 058 * Set the ServletContext attributes to expose as key-value pairs. 059 * Each key will be considered a ServletContext attributes key, 060 * and each value will be used as corresponding attribute value. 061 * <p>Usually, you will use bean references for the values, 062 * to export Spring-defined beans as ServletContext attributes. 063 * Of course, it is also possible to define plain values to export. 064 */ 065 public void setAttributes(Map<String, Object> attributes) { 066 this.attributes = attributes; 067 } 068 069 @Override 070 public void setServletContext(ServletContext servletContext) { 071 if (this.attributes != null) { 072 for (Map.Entry<String, Object> entry : this.attributes.entrySet()) { 073 String attributeName = entry.getKey(); 074 if (logger.isDebugEnabled()) { 075 if (servletContext.getAttribute(attributeName) != null) { 076 logger.debug("Replacing existing ServletContext attribute with name '" + attributeName + "'"); 077 } 078 } 079 servletContext.setAttribute(attributeName, entry.getValue()); 080 if (logger.isTraceEnabled()) { 081 logger.trace("Exported ServletContext attribute with name '" + attributeName + "'"); 082 } 083 } 084 } 085 } 086 087}