com.setronica.ucs.storage.MongoListStorage.java Source code

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Here is the source code for com.setronica.ucs.storage.MongoListStorage.java

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/*
 * Copyright (C) 2014 SETRONICA - setronica.com
 * This source code is available under the terms of the GNU Lesser General Public License
 * as published by The Open Source Initiative (OSI), either version 3 of the License,
 * or (at your option) any later version.
 *
 * UCS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * See the GNU Lesser General Public License for more details.
 * You should have received a copy of the GNU Lesser General Public License.
 */

package com.setronica.ucs.storage;

import com.mongodb.*;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class MongoListStorage<E> implements ListStorage<E>, PersistentStorage {
    protected List<E> data;
    private String mongoDbName;
    private String mongoCollectionName;
    protected DBCollection collection;
    protected MongoClient mongoClient;

    public MongoListStorage(MongoClient mongoClient, String mongoDbName, String mongoCollectionName) {
        this.mongoClient = mongoClient;
        this.mongoDbName = mongoDbName;
        this.mongoCollectionName = mongoCollectionName;
    }

    @Override
    public E get(int index) {
        return data.get(index);
    }

    @Override
    public boolean add(E element) {
        if (data.add(element)) {
            try {
                save(data.size() - 1, element);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
            return true;
        }
        return false;
    }

    @Override
    public void refresh(int index) {
        E element = data.get(index);
        if (element == null)
            return;
        try {
            save(index, element);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    protected void save(int index, E element) throws IOException {
        BasicDBObject object = new BasicDBObject("_id", index);
        object.put("element", writeObject(element));
        collection.insert(object);
    }

    @Override
    public void remove(int index) {
        data.set(index, null);
        collection.remove(new BasicDBObject("_id", index));
    }

    @Override
    public int size() {
        return data.size();
    }

    @Override
    public void open() throws IOException {
        DB db = mongoClient.getDB(mongoDbName);
        collection = db.getCollection(mongoCollectionName);
        if (collection == null) {
            collection = db.createCollection(mongoCollectionName, null);
        }
        collection.setWriteConcern(WriteConcern.ACKNOWLEDGED);

        DBCursor cursor = collection.find();
        data = new ArrayList<E>(cursor.size());
        for (DBObject entry : cursor) {
            Integer index = (Integer) entry.get("_id");
            while (index >= data.size()) {
                data.add(null);
            }
            data.set(index, (E) readObject((byte[]) entry.get("element")));
        }
    }

    //todo compact?

    @Override
    public void close() throws IOException {
    }

    private byte[] writeObject(Object element) throws IOException {
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        ObjectOutput out = new ObjectOutputStream(os);
        out.writeObject(element);
        byte[] val = os.toByteArray();
        out.close();
        os.close();
        return val;
    }

    private Object readObject(byte[] data) throws IOException {
        ByteArrayInputStream bis = new ByteArrayInputStream(data);
        ObjectInput ois = new ObjectInputStream(bis);
        try {
            return ois.readObject();
        } catch (ClassNotFoundException e) {
            throw new IOException(e);
        } finally {
            ois.close();
            bis.close();
        }
    }
}