org.apache.nutch.webapp.common.ServletContextServiceLocator.java Source code

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Here is the source code for org.apache.nutch.webapp.common.ServletContextServiceLocator.java

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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.nutch.webapp.common;

import java.io.IOException;
import java.util.Locale;

import javax.servlet.ServletContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.nutch.plugin.PluginRepository;
import org.apache.nutch.searcher.NutchBean;
import org.apache.nutch.util.NutchConfiguration;

public abstract class ServletContextServiceLocator implements ServiceLocator {

    /**
     * ServiceLocator will be saved in ServletContext under this key
     */
    private static final String KEY = ServletContextServiceLocator.class.getName();

    /**
     * Logger.
     */
    public static final Log LOG = LogFactory.getLog(ServletContextServiceLocator.class);

    /**
     * ServletContext this ServiceLocator is bound to.
     */
    protected ServletContext servletContext;

    /**
     * Active configuration.
     */
    protected Configuration config;

    /**
     * Active PluginRepository.
     */
    private PluginRepository repository;

    /**
     * Active NutchBean.
     */
    private NutchBean bean;

    /**
     * Private Constructor used to create new ServiceLocator when needed.
     *
     * @param servletContext
     */
    private ServletContextServiceLocator(ServletContext servletContext) {
        this.servletContext = servletContext;
        config = NutchConfiguration.get(servletContext);
        repository = PluginRepository.get(config);
        try {
            bean = new NutchBean(config);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * Factory method to get handle to ServiceLocator, or if none exists in
     * ServletContext then one is created.
     *
     * @param context
     * @return ServiceLocator instance bound to ServletContext
     */
    public static ServiceLocator getInstance(ServletContext context) {
        ServiceLocator locator = (ServiceLocator) context.getAttribute(KEY);
        if (locator == null) {
            LOG.info("creating new serviceLocator for context:" + context);
            locator = new ServletContextServiceLocator(context) {
                public SearchForm getSearchForm() {
                    return null;
                }

                public Preferences getPreferences() {
                    return null;
                }

                public Search getSearch() {
                    return null;
                }

                public Locale getLocale() {
                    return null;
                }
            };
            context.setAttribute(KEY, locator);
        }
        return locator;
    }

    public Configuration getConfiguration() {
        return config;
    }

    public PluginRepository getPluginRepository() {
        return repository;
    }

    public NutchBean getNutchBean() {
        return bean;
    }

    public PluginResourceLoader getPluginResourceLoader(ClassLoader loader) {
        return PluginResourceLoader.getInstance(this, loader);
    }

}