/*
 * 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
 *
 *      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.context.support;

import java.util.Map;
import javax.servlet.ServletContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.lang.Nullable;
import org.springframework.web.context.ServletContextAware;

Exporter that takes Spring-defined objects and exposes them as
ServletContext attributes. Usually, bean references will be used
to export Spring-defined beans as ServletContext attributes.
Useful to make Spring-defined beans available to code that is
not aware of Spring at all, but rather just of the Servlet API.
Client code can then use plain ServletContext attribute lookups
to access those objects, despite them being defined in a Spring
application context.
Alternatively, consider using the WebApplicationContextUtils
class to access Spring-defined beans via the WebApplicationContext
interface. This makes client code aware of Spring API, of course.
Author:
Juergen Hoeller
See Also:
ServletContext.getAttribute
WebApplicationContextUtils.getWebApplicationContext
Since:
1.1.4/**
 * Exporter that takes Spring-defined objects and exposes them as
 * ServletContext attributes. Usually, bean references will be used
 * to export Spring-defined beans as ServletContext attributes.
 *
 * <p>Useful to make Spring-defined beans available to code that is
 * not aware of Spring at all, but rather just of the Servlet API.
 * Client code can then use plain ServletContext attribute lookups
 * to access those objects, despite them being defined in a Spring
 * application context.
 *
 * <p>Alternatively, consider using the WebApplicationContextUtils
 * class to access Spring-defined beans via the WebApplicationContext
 * interface. This makes client code aware of Spring API, of course.
 *
 * @author Juergen Hoeller
 * @since 1.1.4
 * @see javax.servlet.ServletContext#getAttribute
 * @see WebApplicationContextUtils#getWebApplicationContext
 */
public class ServletContextAttributeExporter implements ServletContextAware {

	protected final Log logger = LogFactory.getLog(getClass());

	@Nullable
	private Map<String, Object> attributes;


	
Set the ServletContext attributes to expose as key-value pairs.
Each key will be considered a ServletContext attributes key,
and each value will be used as corresponding attribute value.
Usually, you will use bean references for the values,
to export Spring-defined beans as ServletContext attributes.
Of course, it is also possible to define plain values to export.
/**
	 * Set the ServletContext attributes to expose as key-value pairs.
	 * Each key will be considered a ServletContext attributes key,
	 * and each value will be used as corresponding attribute value.
	 * <p>Usually, you will use bean references for the values,
	 * to export Spring-defined beans as ServletContext attributes.
	 * Of course, it is also possible to define plain values to export.
	 */
	public void setAttributes(Map<String, Object> attributes) {
		this.attributes = attributes;
	}

	@Override
	public void setServletContext(ServletContext servletContext) {
		if (this.attributes != null) {
			for (Map.Entry<String, Object> entry : this.attributes.entrySet()) {
				String attributeName = entry.getKey();
				if (logger.isDebugEnabled()) {
					if (servletContext.getAttribute(attributeName) != null) {
						logger.debug("Replacing existing ServletContext attribute with name '" + attributeName + "'");
					}
				}
				servletContext.setAttribute(attributeName, entry.getValue());
				if (logger.isTraceEnabled()) {
					logger.trace("Exported ServletContext attribute with name '" + attributeName + "'");
				}
			}
		}
	}

}