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<title>Berkeley DB Reference Guide: Serializable Entity - Removing the redundant value classes</title>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Java API Tutorial - Serializable Entity</dl></h3></td>
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<p>
<h3 align=center>Serializable Entity - Removing the redundant value classes</h3>
<p>The <b>PartValue</b>, <b>SupplierValue</b> and
<b>ShipmentValue</b> classes have been removed in this example, and the
<b>Part</b>, <b>Supplier</b> and <b>Shipment</b> entity classes are
used in their place.</p>
<hr size=1 noshade>
<p>The serial formats are created with the entity classes.</p>
<blockquote><pre>
public class SampleDatabase
{
    ...
    public SampleDatabase(String homeDirectory, boolean runRecovery)
        throws DbException, FileNotFoundException
    {
        ...
        partKeyFormat = new TupleFormat();
        partValueFormat = new SerialFormat(javaCatalog, <b>Part</b>.class);
        supplierKeyFormat = new TupleFormat();
        supplierValueFormat = new SerialFormat(javaCatalog, <b>Supplier</b>.class);
        shipmentKeyFormat = new TupleFormat();
        shipmentValueFormat = new SerialFormat(javaCatalog, <b>Shipment</b>.class);
        cityKeyFormat = new TupleFormat();
        ...
    }
}
</pre></blockquote>
<hr size=1 noshade>
<p>The index key extractor uses the entity class as well.</p>
<blockquote><pre>
public class SampleDatabase
{
    ...
    private static class SupplierByCityExtractor
        extends TupleSerialKeyExtractor
    {
        private SupplierByCityExtractor(TupleFormat primaryKeyFormat,
                                        SerialFormat valueFormat,
                                        TupleFormat indexKeyFormat)
        {
            super(primaryKeyFormat, valueFormat, indexKeyFormat);
        }
<p>
        public void extractIndexKey(TupleInput primaryKeyInput,
                                    Object valueInput,
                                    TupleOutput indexKeyOutput)
            throws IOException
        {
            <b>Supplier</b> supplierValue = (<b>Supplier</b>) valueInput;
            indexKeyOutput.writeString(supplierValue.getCity());
        }
<p>
        public void clearIndexKey(Object valueInputOutput)
            throws IOException
        {
            throw new UnsupportedOperationException();
        }
    }
<p>
}
</pre></blockquote>
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