com.siemens.scr.avt.ad.io.BatchLoader.java Source code

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Here is the source code for com.siemens.scr.avt.ad.io.BatchLoader.java

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/*
Copyright (c) 2010, Siemens Corporate Research a Division of Siemens Corporation 
All rights reserved.
    
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 com.siemens.scr.avt.ad.io;

import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.Properties;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.filefilter.SuffixFileFilter;
import org.apache.commons.io.filefilter.TrueFileFilter;
import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;

/**
 * A two pass batch loader loading from a given directory.
 * 
 * <ul>
 * <li>Files are filtered by suffixes.</li>
 * <li>Sub-directories are recursively processed.</li>
 * </ul>
 *  
 * @author Xiang Li
 *
 * @param <T> the object type to be loaded.
 */
public abstract class BatchLoader<T> {

    private static Logger logger = Logger.getLogger(BatchLoader.class);

    protected static void initLogging() {
        try {
            Properties props = new Properties();
            props.load(ClassLoader.getSystemResource("log4j.properties").openStream());
            PropertyConfigurator.configure(props);
        } catch (Exception e) {
            System.err.println("unable to load log4j.properties");
        }
    }

    public void loadFromDirectory(File directory) throws Exception {
        preprocess(FileUtils.iterateFiles(directory, new SuffixFileFilter(getSuffix()), TrueFileFilter.INSTANCE));
        load(FileUtils.iterateFiles(directory, new SuffixFileFilter(getSuffix()), TrueFileFilter.INSTANCE));
    }

    protected void load(Iterator<File> fileIterator) throws Exception {
        while (fileIterator.hasNext()) {
            File file = fileIterator.next();
            logger.info("loading file:" + file.getAbsolutePath());
            //         DicomObject dicomObj = DicomParser.read(file);
            T t = readFromFile(file);
            loadSingleObject(t);
            //         loadDicomObject(dicomObj);
        }
    }

    protected abstract String getSuffix();

    protected abstract T readFromFile(File file) throws Exception;

    protected abstract void loadSingleObject(T t);

    protected abstract void preprocessSingleObject(T t);

    protected void preprocess(Iterator<File> fileIterator) throws Exception {
        while (fileIterator.hasNext()) {
            T t = readFromFile(fileIterator.next());
            preprocessSingleObject(t);
        }
    }

}