/**
* License Agreement for OpenSearchServer Pojodbc
*
* Copyright 2008-2013 Emmanuel Keller / Jaeksoft
* Copyright 2014-2015 OpenSearchServer Inc.
*
* 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.jaeksoft.pojodbc;
import java.sql.SQLException;
import java.util.AbstractList;
import java.util.List;
public abstract class PartialList<T> extends AbstractList<T> {
protected int size;
protected List<T> partialList;
protected int currentStart;
protected int rows;
public PartialList(int rows) {
this.rows = rows;
this.currentStart = 0;
this.partialList = null;
this.size = 0;
}
@Override
public T get(int index) {
if (index < currentStart || index >= currentStart + rows)
update(index);
return partialList.get(index - currentStart);
}
protected abstract Query getQuery(Transaction transaction) throws SQLException;
protected abstract Transaction getDatabaseTransaction() throws SQLException;
protected abstract List<T> getResultList(Query query) throws Exception;
protected void update(int start) {
synchronized (this) {
if (partialList != null)
if (currentStart == start && currentStart != -1)
return;
Transaction transaction = null;
try {
transaction = getDatabaseTransaction();
Query query = getQuery(transaction);
currentStart = start;
query.setFirstResult(currentStart);
query.setMaxResults(rows);
partialList = getResultList(query);
size = query.getResultCount();
} catch (Exception e) {
partialList = null;
size = 0;
throw new RuntimeException(e);
} finally {
if (transaction != null)
transaction.close();
}
}
}
@Override
public int size() {
return size;
}
@Override
public String toString() {
return "start: " + currentStart + " size: " + size;
}
}