MaxRowsDocumentSource.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.metamodel.data;

/**
 * A {@link DocumentSource} that has a max rows condition on it, that will make
 * it stop serving documents after a certain limit.
 */
public class MaxRowsDocumentSource implements DocumentSource {

    private final DocumentSource _delegate;
    private volatile int _rowsLeft;

    public MaxRowsDocumentSource(DocumentSource delegate, int maxRows) {
        _delegate = delegate;
        _rowsLeft = maxRows;
    }

    @Override
    public Document next() {
        if (_rowsLeft > 0) {
            Document next = _delegate.next();
            _rowsLeft--;
            return next;
        }
        return null;
    }

    @Override
    public void close() {
        _delegate.close();
    }

}