common.services.generic.GenericCacheService.java Source code

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Here is the source code for common.services.generic.GenericCacheService.java

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/*
 *  Copyright 2010 demchuck.dima@gmail.com
 *
 *  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 common.services.generic;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import org.apache.log4j.Logger;
import org.springframework.core.io.Resource;

/**
 *
 * @param <T> 
 * @author demchuck.dima@gmail.com
 */
public abstract class GenericCacheService<T> implements IGenericCacheService<T> {
    protected final Logger logger = Logger.getLogger(this.getClass());
    /* path to folder where the cache will be stored */
    protected String path;
    protected T cached_object;

    public void init() {
        StringBuilder sb = new StringBuilder();
        common.utils.MiscUtils.checkNotNull(path, "path", sb);
        if (sb.length() > 0) {
            throw new NullPointerException(sb.toString());
        }
    }

    @Override
    public synchronized void clearCache() {
        File f = new File(path);
        File[] files = f.listFiles();
        for (File file : files) {
            file.delete();
        }
        cached_object = null;
    }

    @Override
    public synchronized void refreshCache() {
        T tmp = getFromDB();
        cached_object = tmp;
        saveToFile();
    }

    public synchronized T getObject() {
        if (cached_object != null) {
            //logger.info("rubrication from class");
            return cached_object;
        } else {
            cached_object = getFromFile();
            if (cached_object != null) {
                //logger.info("rubrication from file");
                return cached_object;
            } else {
                cached_object = getFromDB();
                if (cached_object != null) {
                    //logger.info("rubrication from DB");
                    saveToFile();
                    return cached_object;
                } else {
                    return null;
                }
            }
        }
    }

    @Override
    public T getFromFile() {
        File f = new File(path, "cache.tmp");
        if (!f.exists())
            return null;
        try {
            FileInputStream fi = new FileInputStream(f);
            ObjectInputStream si = new ObjectInputStream(fi);
            T tmp = (T) si.readObject();
            si.close();
            fi.close();
            return tmp;
        } catch (IOException ex) {
            logger.error("failed to load cache path = " + path, ex);
            return null;
        } catch (ClassNotFoundException ex) {
            logger.error("failed to load cache path = " + path, ex);
            return null;
        }
    }

    @Override
    public boolean saveToFile() {
        if (cached_object == null)
            return false;
        try {
            File f = new File(path, "cache.tmp");
            if (f.exists())
                f.delete();
            f.createNewFile();
            FileOutputStream fo = new FileOutputStream(f);
            ObjectOutputStream so = new ObjectOutputStream(fo);
            so.writeObject(cached_object);
            so.flush();
            so.close();
            fo.close();
            return true;
        } catch (IOException ex) {
            logger.error("failed to save cache path = " + path, ex);
            return false;
        }
    }

    public void setPath(Resource res) {
        try {
            File f = res.getFile();
            if (f.exists()) {
                if (f.isFile()) {
                    f.delete();
                    f.mkdir();
                }
            } else {
                f.mkdirs();
                //f.mkdir();
            }
            if (f.exists() && f.isDirectory())
                path = f.getCanonicalPath() + "/";
            else
                throw new NullPointerException("cache folder not found for " + getClass().getName());
        } catch (IOException e) {
            path = null;
            throw new NullPointerException("cache folder not found for " + getClass().getName());
        }
        //System.out.println("----------------------------path = "+this.path);
    }
}