org.sakaiproject.component.impl.SakaiContextLoader.java Source code

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Here is the source code for org.sakaiproject.component.impl.SakaiContextLoader.java

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/**********************************************************************************
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 * $Id$
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 *
 * Copyright (c) 2005, 2006, 2007, 2008 Sakai Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ECL-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.sakaiproject.component.impl;

import java.io.File;

import javax.servlet.ServletContext;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.sakaiproject.component.cover.ComponentManager;
import org.sakaiproject.component.cover.ServerConfigurationService;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.AnnotationConfigUtils;
import org.springframework.core.io.FileSystemResource;
import org.springframework.web.context.ConfigurableWebApplicationContext;
import org.springframework.web.context.ContextLoader;
import org.springframework.web.context.WebApplicationContext;

/**
 * <p>
 * Sakai's extension to Spring's ContextLoader - adds the location of the ComponentManager shared AC, linking the local AC to it as parent, and loading localy hosted components into shared.
 * </p>
 */
public class SakaiContextLoader extends ContextLoader {
    private static final Log log = LogFactory.getLog(SakaiContextLoader.class);
    public static final String SPRING_CONTEXT_SUFFIX = "-context.xml";

    /**
      * Allows loading/override of custom bean definitions from sakai.home
      *
      * <p>The pattern is the 'servlet_name-context.xml'</p>
      *
      * @param servletContext current servlet context
      * @return the new WebApplicationContext
      * @throws org.springframework.beans.BeansException
      *          if the context couldn't be initialized
      */
    @Override
    public WebApplicationContext initWebApplicationContext(ServletContext servletContext) throws BeansException {

        ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) super.initWebApplicationContext(
                servletContext);
        // optionally look in sakai home for additional bean deifinitions to load
        if (cwac != null) {
            final String servletName = servletContext.getServletContextName();
            String location = getHomeBeanDefinitionIfExists(servletName);
            if (StringUtils.isNotBlank(location)) {
                log.debug("Servlet " + servletName + " is attempting to load bean definition [" + location + "]");
                XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(
                        (BeanDefinitionRegistry) cwac.getBeanFactory());
                try {
                    int loaded = reader.loadBeanDefinitions(new FileSystemResource(location));
                    log.info("Servlet " + servletName + " loaded " + loaded + " beans from [" + location + "]");
                    AnnotationConfigUtils.registerAnnotationConfigProcessors(reader.getRegistry());
                    cwac.getBeanFactory().preInstantiateSingletons();
                } catch (BeanDefinitionStoreException bdse) {
                    log.warn("Failure loading beans from [" + location + "]", bdse);
                } catch (BeanCreationException bce) {
                    log.warn("Failure instantiating beans from [" + location + "]", bce);
                }
            }
        }
        return cwac;
    }

    /**
     * Spring allows a parent ApplicationContext to be set during the creation of a new ApplicationContext
     *
     * Sakai sets the SakaiApplicationContext as the parent which managed by the ComponentManager
     * 
     * @param servletContext (not used)
     * @return the shared SakaiApplicationContext
     */
    @Override
    protected ApplicationContext loadParentContext(ServletContext servletContext) throws BeansException {
        // get the component manager (we know it's a SpringCompMgr) and from that the shared AC
        ConfigurableApplicationContext sharedAc = ((SpringCompMgr) ComponentManager.getInstance())
                .getApplicationContext();

        return sharedAc;
    }

    private String getHomeBeanDefinitionIfExists(String servletName) {
        if (StringUtils.isBlank(servletName)) {
            return null;
        }

        if (StringUtils.isNotBlank(servletName)) {
            String name = servletName + SPRING_CONTEXT_SUFFIX;
            String path = ServerConfigurationService.getSakaiHomePath();
            String location = path + name;

            log.debug("Servlet " + servletName + " is checking for a bean definition at sakai.home/" + name);
            if (new File(location).canRead()) {
                log.info("Servlet " + servletName + " located an additional bean definition at sakai.home/" + name);
                return location;
            } else {
                log.debug("Servlet " + servletName + " did not find a bean definition at sakai.home/" + name);
            }
        }
        return null;
    }
}