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<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title> Creating Tuple Key Bindings </title> <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.62.4" /> <link rel="home" href="index.html" title="Berkeley DB Collections Tutorial" /> <link rel="up" href="Tuple.html" title="Chapter 5. 		Using Tuples 	" /> <link rel="previous" href="tupleswithkeycreators.html" title=" 		Using Tuples with Key Creators 	" /> <link rel="next" href="tuple-serialentitybindings.html" title=" Creating Tuple-Serial Entity Bindings " /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center"> Creating Tuple Key Bindings </th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="tupleswithkeycreators.html">Prev</a> </td> <th width="60%" align="center">Chapter 5. Using Tuples </th> <td width="20%" align="right"> <a accesskey="n" href="tuple-serialentitybindings.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="tuplekeybindings"></a> Creating Tuple Key Bindings </h2> </div> </div> <div></div> </div> <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 <tt class="classname">PartKey</tt>, <tt class="classname">SupplierKey</tt> and <tt class="classname">ShipmentKey</tt> classes no longer implement the <a href="http://java.sun.com/j2se/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 <tt class="classname">Part</tt> key, <tt class="classname">Supplier</tt> key, and <tt class="classname">Shipment</tt> key, the <tt class="classname">SampleViews</tt> class was changed in this example to create a custom <a href="../../java/com/sleepycat/bind/tuple/TupleBinding.html" target="_top">TupleBinding</a> instead of a <a 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"><b class="userinput"><tt>import com.sleepycat.bind.tuple.TupleBinding; ...</tt></b> public class SampleViews { ... public SampleViews(SampleDatabase db) { ... ClassCatalog catalog = db.getClassCatalog(); <b class="userinput"><tt> 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);</tt></b> ... } } </pre> <p> For the City key, however, a custom binding class is not needed because the key class is a primitive Java type, <a href="http://java.sun.com/j2se/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 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, <tt class="classname">PartKeyBinding</tt>, <tt class="classname">SupplierKeyBinding</tt> and <tt class="classname">ShipmentKeyBinding</tt>, are defined by extending the <a href="../../java/com/sleepycat/bind/tuple/TupleBinding.html" target="_top">TupleBinding</a> class. The <a href="../../java/com/sleepycat/bind/tuple/TupleBinding.html" target="_top">TupleBinding</a> abstract class implements the <a 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 href="../../java/com/sleepycat/bind/tuple/TupleInput.html" target="_top">TupleInput</a> parameter and written using the <a href="../../java/com/sleepycat/bind/tuple/TupleOutput.html" target="_top">TupleOutput</a> parameter. </p> <a id="tuple_partkeybinding"></a> <pre class="programlisting"><b class="userinput"><tt>import com.sleepycat.bind.tuple.TupleBinding; import com.sleepycat.bind.tuple.TupleInput; import com.sleepycat.bind.tuple.TupleOutput; ...</tt></b> public class SampleViews { ... <b class="userinput"><tt>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()); } }</tt></b> ... } </pre> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="tupleswithkeycreators.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="Tuple.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="tuple-serialentitybindings.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top"> Using Tuples with Key Creators </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> Creating Tuple-Serial Entity Bindings </td> </tr> </table> </div> </body> </html>