org.apache.nutch.plugin.NutchConfiguration.java Source code

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Here is the source code for org.apache.nutch.plugin.NutchConfiguration.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.plugin;

import java.util.Map.Entry;
import java.util.Properties;
import java.util.UUID;

import org.apache.hadoop.conf.Configuration;

/** Utility to create Hadoop {@link Configuration}s that include Nutch-specific
 * resources.  */
public class NutchConfiguration {
    public static final String UUID_KEY = "nutch.conf.uuid";

    private NutchConfiguration() {
    } // singleton

    /*
     * Configuration.hashCode() doesn't return values that
     * correspond to a unique set of parameters. This is a workaround
     * so that we can track instances of Configuration created by Nutch.
     */
    private static void setUUID(Configuration conf) {
        UUID uuid = UUID.randomUUID();
        conf.set(UUID_KEY, uuid.toString());
    }

    /**
     * Retrieve a Nutch UUID of this configuration object, or null
     * if the configuration was created elsewhere.
     * @param conf configuration instance
     * @return uuid or null
     */
    public static String getUUID(Configuration conf) {
        return conf.get(UUID_KEY);
    }

    /** Create a {@link Configuration} for Nutch. This will load the standard
     * Nutch resources, <code>nutch-default.xml</code> and
     * <code>nutch-site.xml</code> overrides.
     */
    public static Configuration create() {
        Configuration conf = new Configuration();
        setUUID(conf);
        addNutchResources(conf);
        return conf;
    }

    /** Create a {@link Configuration} from supplied properties.
     * @param addNutchResources if true, then first <code>nutch-default.xml</code>,
     * and then <code>nutch-site.xml</code> will be loaded prior to applying the
     * properties. Otherwise these resources won't be used.
     * @param nutchProperties a set of properties to define (or override)
     */
    public static Configuration create(boolean addNutchResources, Properties nutchProperties) {
        Configuration conf = new Configuration();
        setUUID(conf);
        if (addNutchResources) {
            addNutchResources(conf);
        }
        for (Entry<Object, Object> e : nutchProperties.entrySet()) {
            conf.set(e.getKey().toString(), e.getValue().toString());
        }
        return conf;
    }

    /**
     * Add the standard Nutch resources to {@link Configuration}.
     * 
     * @param conf               Configuration object to which
     *                           configuration is to be added.
     */
    private static Configuration addNutchResources(Configuration conf) {
        conf.addResource("nutch-default.xml");
        conf.addResource("nutch-site.xml");
        return conf;
    }
}