AbstractHBaseRecordScanner.java

/*
 * Copyright 2012 NGDATA nv
 *
 * 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 org.lilyproject.repository.impl;

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

import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.ResultScanner;
import org.lilyproject.repository.api.Record;
import org.lilyproject.repository.api.RepositoryException;

abstract class AbstractHBaseRecordScanner<T extends Record> {
    private final ResultScanner hbaseScanner;

    AbstractHBaseRecordScanner(ResultScanner hbaseScanner) {
        this.hbaseScanner = hbaseScanner;
    }

    abstract T decode(Result result) throws RepositoryException, InterruptedException;

    public T next() throws RepositoryException, InterruptedException {
        Result result;
        try {
            result = hbaseScanner.next();
        } catch (IOException e) {
            throw new RepositoryException(e);
        }

        if (result == null) {
            // no more results
            return null;
        }

        return decode(result);
    }

    public void close() {
        hbaseScanner.close();
    }

    public Iterator<T> iterator() {
        return new Iterator<T>() {
            private T next;

            @Override
            public boolean hasNext() {
                if (next != null) {
                    return true;
                } else {
                    try {
                        next = AbstractHBaseRecordScanner.this.next();
                    } catch (RepositoryException e) {
                        throw new RuntimeException(e);
                    } catch (InterruptedException e) {
                        Thread.currentThread().interrupt();
                        throw new RuntimeException(e);
                    }
                    return next != null;
                }
            }

            @Override
            public T next() {
                if (!hasNext()) {
                    return null;
                }

                T result = next;
                next = null;
                return result;
            }

            @Override
            public void remove() {
                throw new UnsupportedOperationException();
            }
        };
    }
}