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/*
* Copyright (c) 2006 Israfil Consulting Services Corporation
* Copyright (c) 2006 Christian Edward Gruber
* All Rights Reserved
*
* This software is licensed under the Berkeley Standard Distribution license,
* (BSD license), as defined below:
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. Neither the name of Israfil Consulting Services nor the names of its contributors
* may be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* $Id: IterableResultSet.java 26 2006-02-13 16:35:44Z cgruber $
*/
package net.israfil.foundation.collections;
import java.lang.ref.WeakReference;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* A simple wrapper that provides an Iterable implementation back-ended
* by a result-set. Allows a ResultSet to be used in a JDK 5.0 extended
* for-loop syntax.
*
* No result set can have more than one Iterable wrapper around it at a time.
* However, it is impossible for this object to know implicitly when it is
* no longer required (to free the reference). Therefore, when this
* wrapper is concluded, it should be disposed of via the dispose() method.
*
* @author <a href="mailto:cgruber@israfil.net">Christian Edward Gruber </a>
*/
public class IterableResultSet implements Iterable<Map<String,Object>> {
protected static final Map<ResultSet,IterableResultSet> iterables = new WeakHashMap<ResultSet,IterableResultSet>();
protected final WeakReference<ResultSet> resultRef;
public IterableResultSet(ResultSet result) {
if (iterables.containsKey(result)) throw new RuntimeException("Cannot have two IterableResultSet wrappers around the same resultset.");
this.resultRef = new WeakReference<ResultSet>(result);
}
public Iterator<Map<String,Object>> iterator() {
if (resultRef.get() == null) throw new RuntimeException("ResultSet object not available to iterate.");
return new ResultSetIterator(resultRef.get());
}
public void dispose() {
ResultSet rs = resultRef.get();
if (rs == null) return;
if (iterables.containsKey(rs)) {
iterables.get(rs).dispose();
}
resultRef.clear();
}
public static class ResultSetIterator implements Iterator<Map<String,Object>> {
private static final Logger logger = Logger.getLogger(ResultSetIterator.class.getName());
protected ResultSet result;
boolean hasNext = true;
public ResultSetIterator(ResultSet result) {
this.result = result;
try {
hasNext = result.first();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
public boolean hasNext() {
return hasNext;
}
public Map<String,Object> next() {
try {
Map<String,Object> row = new HashMap<String,Object>();
for(int i = 1; i <= result.getMetaData().getColumnCount(); i++) {
row.put(result.getMetaData().getColumnName(i),result.getObject(i));
}
hasNext = result.next();
return row;
} catch (SQLException e) {
logger.log(Level.FINER,"SQLException thrown while iterating across result set.",e);
return null;
}
}
public void remove() {
throw new UnsupportedOperationException("Removal of records from underlying result set not supported.");
}
public void dispose() {
if (iterables.containsKey(result)) iterables.remove(result);
result = null;
}
public void finalize() throws Throwable {
dispose();
super.finalize();
}
}
}
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