com.petpet.c3po.dao.mongo.MongoIterator.java Source code

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Here is the source code for com.petpet.c3po.dao.mongo.MongoIterator.java

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/*******************************************************************************
 * Copyright 2013 Petar Petrov <me@petarpetrov.org>
 * 
 * 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.petpet.c3po.dao.mongo;

import java.util.Iterator;
import java.util.NoSuchElementException;

import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.petpet.c3po.api.model.Model;

/**
 * Wraps a Mongo {@link DBCursor} into an iterator.
 * 
 * @author Petar Petrov <me@petarpetrov.org>
 * 
 * @param <E>
 *          the model class that is wrapped.
 */
public class MongoIterator<E extends Model> implements Iterator<E> {

    /**
     * The internal iterator used.
     */
    private Iterator<DBObject> iter;

    /**
     * The deserializer for each object.
     */
    private MongoModelDeserializer deserializer;

    /**
     * Creates an iterator.
     * 
     * @param deserializer
     *          the deserializer to use.
     * @param cursor
     *          the cursor to use.
     * @throws IllegalArgumentException
     *           if the desearializer is null.
     */
    public MongoIterator(MongoModelDeserializer deserializer, DBCursor cursor) {
        if (cursor != null)
            this.iter = cursor.iterator();

        if (deserializer == null) {
            throw new IllegalArgumentException("Deserializer cannot be null");
        }

        this.deserializer = deserializer;
    }

    /**
     * @return true if the iterator has a next element, false otherwise.
     */
    @Override
    public boolean hasNext() {
        if (this.iter == null) {
            return false;
        }

        return this.iter.hasNext();
    }

    /**
     * Returns the next element (after deserialization) if the iterator has a next
     * element. This method should be called only after
     * {@link MongoIterator#hasNext()} call has returned true.
     * 
     * @throws NoSuchElementException
     *           if there is no next element or the iterator is null.
     */
    @Override
    public E next() {
        if (this.iter == null) {
            throw new NoSuchElementException("The iterator was null");
        }

        DBObject next = this.iter.next();

        return (E) this.deserializer.deserialize(next);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void remove() {
        this.iter.remove();

    }

}