com.iflytek.spider.crawl.SignatureFactory.java Source code

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Here is the source code for com.iflytek.spider.crawl.SignatureFactory.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 com.iflytek.spider.crawl;

// Commons Logging imports

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;

import com.iflytek.spider.util.ObjectCache;

/**
 * Factory class, which instantiates a Signature implementation according to the
 * current Configuration configuration. This newly created instance is cached in the
 * Configuration instance, so that it could be later retrieved.
 * 
 * @author Andrzej Bialecki <ab@getopt.org>
 */
public class SignatureFactory {
    private static final Log LOG = LogFactory.getLog(SignatureFactory.class);

    private SignatureFactory() {
    } // no public ctor

    /** Return the default Signature implementation. */
    public static Signature getSignature(Configuration conf) {
        String clazz = conf.get("db.signature.class", MD5Signature.class.getName());
        ObjectCache objectCache = ObjectCache.get(conf);
        Signature impl = (Signature) objectCache.getObject(clazz);
        if (impl == null) {
            try {
                if (LOG.isInfoEnabled()) {
                    LOG.info("Using Signature impl: " + clazz);
                }
                Class<?> implClass = Class.forName(clazz);
                impl = (Signature) implClass.newInstance();
                impl.setConf(conf);
                objectCache.setObject(clazz, impl);
            } catch (Exception e) {
                throw new RuntimeException("Couldn't create " + clazz, e);
            }
        }
        return impl;
    }
}