221 lines
8.0 KiB
HTML
221 lines
8.0 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>
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Creating Tuple Key Bindings
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</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.62.4" />
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<link rel="home" href="index.html" title="Berkeley DB Collections Tutorial" />
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<link rel="up" href="Tuple.html" title="Chapter 5. 		Using Tuples 	" />
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<link rel="previous" href="tupleswithkeycreators.html" title=" 		Using Tuples with Key Creators 	" />
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<link rel="next" href="tuple-serialentitybindings.html" title=" Creating Tuple-Serial Entity Bindings " />
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</head>
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<body>
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<div class="navheader">
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">
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Creating Tuple Key Bindings
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</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="tupleswithkeycreators.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 5.
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Using Tuples
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="tuple-serialentitybindings.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="tuplekeybindings"></a>
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Creating Tuple Key Bindings
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</h2>
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</div>
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</div>
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<div></div>
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</div>
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<p>
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Serial bindings were used in prior examples as key bindings, and
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keys were stored as serialized objects. In this example, a tuple
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binding is used for each key since keys will be stored as tuples.
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Because keys are no longer stored as serialized objects, the
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<tt class="classname">PartKey</tt>, <tt class="classname">SupplierKey</tt> and <tt class="classname">ShipmentKey</tt> classes
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no longer implement the
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<a href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/Serializable.html" target="_top">Serializable</a>
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interface (this is the only change to these classes and is not
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shown below).
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</p>
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<p>
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For the <tt class="classname">Part</tt> key, <tt class="classname">Supplier</tt> key,
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and <tt class="classname">Shipment</tt> key, the
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<tt class="classname">SampleViews</tt> class was changed in this example to create a
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custom
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<a href="../../java/com/sleepycat/bind/tuple/TupleBinding.html" target="_top">TupleBinding</a>
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instead of a
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<a href="../../java/com/sleepycat/bind/serial/SerialBinding.html" target="_top">SerialBinding</a>.
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The custom tuple key binding classes are defined further below.
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</p>
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<a id="tuple_sampleviews"></a>
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<pre class="programlisting"><b class="userinput"><tt>import com.sleepycat.bind.tuple.TupleBinding;
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...</tt></b>
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public class SampleViews
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{
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...
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public SampleViews(SampleDatabase db)
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{
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...
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ClassCatalog catalog = db.getClassCatalog();
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<b class="userinput"><tt> EntryBinding partKeyBinding =
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new PartKeyBinding();
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EntityBinding partDataBinding =
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new PartBinding(catalog, PartData.class);
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EntryBinding supplierKeyBinding =
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new SupplierKeyBinding();
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EntityBinding supplierDataBinding =
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new SupplierBinding(catalog, SupplierData.class);
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EntryBinding shipmentKeyBinding =
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new ShipmentKeyBinding();
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EntityBinding shipmentDataBinding =
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new ShipmentBinding(catalog, ShipmentData.class);
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EntryBinding cityKeyBinding =
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TupleBinding.getPrimitiveBinding(String.class);</tt></b>
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...
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}
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} </pre>
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<p>
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For the City key, however, a custom binding class is not needed
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because the key class is a primitive Java type,
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<a href="http://java.sun.com/j2se/1.5.0/docs/api/java/lang/String.html" target="_top">String</a>.
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For any primitive Java type, a tuple binding may be created using the
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<a href="../../java/com/sleepycat/bind/tuple/TupleBinding.html#getPrimitiveBinding(java.lang.Class)" target="_top">TupleBinding.getPrimitiveBinding</a>
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static method.
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</p>
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<p>
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The custom key binding classes, <tt class="classname">PartKeyBinding</tt>,
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<tt class="classname">SupplierKeyBinding</tt> and <tt class="classname">ShipmentKeyBinding</tt>, are
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defined by extending the
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<a href="../../java/com/sleepycat/bind/tuple/TupleBinding.html" target="_top">TupleBinding</a>
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class. The
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<a href="../../java/com/sleepycat/bind/tuple/TupleBinding.html" target="_top">TupleBinding</a>
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abstract class implements the
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<a href="../../java/com/sleepycat/bind/EntryBinding.html" target="_top">EntryBinding</a>
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interface, and is used for one-to-one bindings between tuples and
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objects. Each binding class implements two methods for converting
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between tuples and objects. Tuple fields are read using the
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<a href="../../java/com/sleepycat/bind/tuple/TupleInput.html" target="_top">TupleInput</a>
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parameter and written using the
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<a href="../../java/com/sleepycat/bind/tuple/TupleOutput.html" target="_top">TupleOutput</a>
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parameter.
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</p>
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<a id="tuple_partkeybinding"></a>
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<pre class="programlisting"><b class="userinput"><tt>import com.sleepycat.bind.tuple.TupleBinding;
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import com.sleepycat.bind.tuple.TupleInput;
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import com.sleepycat.bind.tuple.TupleOutput;
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...</tt></b>
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public class SampleViews
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{
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...
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<b class="userinput"><tt>private static class PartKeyBinding extends TupleBinding
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{
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private PartKeyBinding()
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{
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}
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public Object entryToObject(TupleInput input)
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{
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String number = input.readString();
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return new PartKey(number);
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}
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public void objectToEntry(Object object, TupleOutput output)
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{
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PartKey key = (PartKey) object;
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output.writeString(key.getNumber());
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}
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}
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...
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private static class SupplierKeyBinding extends TupleBinding
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{
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private SupplierKeyBinding()
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{
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}
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public Object entryToObject(TupleInput input)
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{
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String number = input.readString();
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return new SupplierKey(number);
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}
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public void objectToEntry(Object object, TupleOutput output)
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{
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SupplierKey key = (SupplierKey) object;
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output.writeString(key.getNumber());
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}
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}
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...
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private static class ShipmentKeyBinding extends TupleBinding
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{
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private ShipmentKeyBinding()
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{
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}
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public Object entryToObject(TupleInput input)
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{
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String partNumber = input.readString();
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String supplierNumber = input.readString();
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return new ShipmentKey(partNumber, supplierNumber);
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}
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public void objectToEntry(Object object, TupleOutput output)
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{
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ShipmentKey key = (ShipmentKey) object;
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output.writeString(key.getPartNumber());
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output.writeString(key.getSupplierNumber());
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}
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}</tt></b>
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...
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} </pre>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="tupleswithkeycreators.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="Tuple.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="tuple-serialentitybindings.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">
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Using Tuples with Key Creators
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</td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top">
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Creating Tuple-Serial Entity Bindings
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</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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