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/** |
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$Id $ |
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Copyright (C) 2012 Nicklas Nordborg |
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This file is part of BASE - BioArray Software Environment. |
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Available at http://base.thep.lu.se/ |
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BASE is free software; you can redistribute it and/or |
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modify it under the terms of the GNU General Public License |
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as published by the Free Software Foundation; either version 3 |
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of the License, or (at your option) any later version. |
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|
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BASE is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU General Public License for more details. |
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You should have received a copy of the GNU General Public License |
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along with BASE. If not, see <http://www.gnu.org/licenses/>. |
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*/ |
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package net.sf.basedb.util.query; |
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import java.util.Iterator; |
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import net.sf.basedb.core.BasicItem; |
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import net.sf.basedb.core.DbControl; |
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import net.sf.basedb.core.ItemQuery; |
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/** |
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Helper class for executing multiple queries and return the result as |
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a single iterator. The queries are executed in the order that they |
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are given, if a query doesn't return any result, the iterator continues |
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with the next query. As soon as a query returns at least one |
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result, no more queries are executed. |
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@author nicklas |
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@since 3.2 |
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*/ |
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public class MultiQueryIterator<E extends BasicItem> |
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implements Iterator<E> |
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{ |
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|
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/** |
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Create a new iterator for the given list of queries. There must |
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be at least one query. |
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@param dc The DbControl to use when executing the queries |
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@param queries An array of queries to execute |
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*/ |
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@SafeVarargs |
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public static <E extends BasicItem> Iterator<E> get(DbControl dc, ItemQuery<? extends E>... queries) |
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{ |
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if (queries == null || queries.length == 0) |
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{ |
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throw new NullPointerException("queries"); |
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} |
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return new MultiQueryIterator<E>(dc, queries); |
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} |
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|
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private final DbControl dc; |
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private final ItemQuery<? extends E>[] queries; |
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|
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private Iterator<? extends E> current; |
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private int nextQuery; |
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private int numReturned; |
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private MultiQueryIterator(DbControl dc, ItemQuery<? extends E>[] queries) |
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{ |
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this.dc = dc; |
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this.queries = queries; |
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this.current = queries[0].iterate(dc); |
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nextQuery = 1; |
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} |
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|
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/* |
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From the Iterator interface |
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--------------------------- |
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*/ |
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@Override |
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public boolean hasNext() |
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{ |
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while (!current.hasNext() && nextQuery < queries.length) |
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{ |
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if (numReturned > 0) return false; |
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if (queries[nextQuery] != null) |
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{ |
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current = queries[nextQuery].iterate(dc); |
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} |
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nextQuery++; |
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} |
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return current.hasNext(); |
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} |
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|
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@Override |
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public E next() |
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{ |
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if (hasNext()) numReturned++; |
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return current.next(); |
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} |
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|
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@Override |
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public void remove() |
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{ |
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throw new UnsupportedOperationException(); |
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} |
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// ------------------------------ |
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|
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} |