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Creating Tuple Key Bindings
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<h2 class="title" style="clear: both"><a id="tuplekeybindings"></a>
Creating Tuple Key Bindings
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<p>
Serial bindings were used in prior examples as key bindings, and
keys were stored as serialized objects. In this example, a tuple
binding is used for each key since keys will be stored as tuples.
Because keys are no longer stored as serialized objects, the
<code class="classname">PartKey</code>, <code class="classname">SupplierKey</code> and <code class="classname">ShipmentKey</code> classes
no longer implement the
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/io/Serializable.html" target="_top">Serializable</a>
interface (this is the only change to these classes and is not
shown below).
</p>
<p>
For the <code class="classname">Part</code> key, <code class="classname">Supplier</code> key,
and <code class="classname">Shipment</code> key, the
<code class="classname">SampleViews</code> class was changed in this example to create a
custom
<a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleBinding.html" target="_top">TupleBinding</a>
instead of a
<a class="ulink" href="../../java/com/sleepycat/bind/serial/SerialBinding.html" target="_top">SerialBinding</a>.
The custom tuple key binding classes are defined further below.
</p>
<a id="tuple_sampleviews"></a>
<pre class="programlisting"><strong class="userinput"><code>import com.sleepycat.bind.tuple.TupleBinding;
...</code></strong>
public class SampleViews
{
...
public SampleViews(SampleDatabase db)
{
...
ClassCatalog catalog = db.getClassCatalog();
<strong class="userinput"><code> EntryBinding partKeyBinding =
new PartKeyBinding();
EntityBinding partDataBinding =
new PartBinding(catalog, PartData.class);
EntryBinding supplierKeyBinding =
new SupplierKeyBinding();
EntityBinding supplierDataBinding =
new SupplierBinding(catalog, SupplierData.class);
EntryBinding shipmentKeyBinding =
new ShipmentKeyBinding();
EntityBinding shipmentDataBinding =
new ShipmentBinding(catalog, ShipmentData.class);
EntryBinding cityKeyBinding =
TupleBinding.getPrimitiveBinding(String.class);</code></strong>
...
}
} </pre>
<p>
For the City key, however, a custom binding class is not needed
because the key class is a primitive Java type,
<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/lang/String.html" target="_top">String</a>.
For any primitive Java type, a tuple binding may be created using the
<a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleBinding.html#getPrimitiveBinding(java.lang.Class)" target="_top">TupleBinding.getPrimitiveBinding</a>
static method.
</p>
<p>
The custom key binding classes, <code class="classname">PartKeyBinding</code>,
<code class="classname">SupplierKeyBinding</code> and <code class="classname">ShipmentKeyBinding</code>, are
defined by extending the
<a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleBinding.html" target="_top">TupleBinding</a>
class. The
<a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleBinding.html" target="_top">TupleBinding</a>
abstract class implements the
<a class="ulink" href="../../java/com/sleepycat/bind/EntryBinding.html" target="_top">EntryBinding</a>
interface, and is used for one-to-one bindings between tuples and
objects. Each binding class implements two methods for converting
between tuples and objects. Tuple fields are read using the
<a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleInput.html" target="_top">TupleInput</a>
parameter and written using the
<a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleOutput.html" target="_top">TupleOutput</a>
parameter.
</p>
<a id="tuple_partkeybinding"></a>
<pre class="programlisting"><strong class="userinput"><code>import com.sleepycat.bind.tuple.TupleBinding;
import com.sleepycat.bind.tuple.TupleInput;
import com.sleepycat.bind.tuple.TupleOutput;
...</code></strong>
public class SampleViews
{
...
<strong class="userinput"><code>private static class PartKeyBinding extends TupleBinding
{
private PartKeyBinding()
{
}
public Object entryToObject(TupleInput input)
{
String number = input.readString();
return new PartKey(number);
}
public void objectToEntry(Object object, TupleOutput output)
{
PartKey key = (PartKey) object;
output.writeString(key.getNumber());
}
}
...
private static class SupplierKeyBinding extends TupleBinding
{
private SupplierKeyBinding()
{
}
public Object entryToObject(TupleInput input)
{
String number = input.readString();
return new SupplierKey(number);
}
public void objectToEntry(Object object, TupleOutput output)
{
SupplierKey key = (SupplierKey) object;
output.writeString(key.getNumber());
}
}
...
private static class ShipmentKeyBinding extends TupleBinding
{
private ShipmentKeyBinding()
{
}
public Object entryToObject(TupleInput input)
{
String partNumber = input.readString();
String supplierNumber = input.readString();
return new ShipmentKey(partNumber, supplierNumber);
}
public void objectToEntry(Object object, TupleOutput output)
{
ShipmentKey key = (ShipmentKey) object;
output.writeString(key.getPartNumber());
output.writeString(key.getSupplierNumber());
}
}</code></strong>
...
} </pre>
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