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165 lines
6.6 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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<html xmlns="http://www.w3.org/1999/xhtml">
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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>Creating Collections with Entity Bindings</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 V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB Java Edition Collections Tutorial" />
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<link rel="up" href="Entity.html" title="Chapter 4. Using Entity Classes" />
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<link rel="prev" href="creatingentitybindings.html" title="Creating Entity Bindings" />
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<link rel="next" href="entitieswithcollections.html" title="Using Entities with Collections" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 12.2.7.5</p>
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</div>
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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 Collections with Entity 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="creatingentitybindings.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 4.
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Using Entity Classes
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="entitieswithcollections.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="collectionswithentities"></a>
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Creating Collections with Entity Bindings
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</h2>
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</div>
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</div>
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</div>
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<p>
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Stored map objects are created in this example in the same way
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as in prior examples, but using entity bindings in place of value
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bindings. All value objects passed and returned to the Java
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collections API are then actually entity objects (<code class="classname">Part</code>,
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<code class="classname">Supplier</code> and <code class="classname">Shipment</code>). The application no longer
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deals directly with plain value objects (<code class="classname">PartData</code>,
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<code class="classname">SupplierData</code> and <code class="classname">ShipmentData</code>).
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</p>
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<p>
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Since the <code class="literal">partDataBinding</code>, <code class="literal">supplierDataBinding</code>
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and <code class="literal">shipmentDataBinding</code> were defined as entity bindings in
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the prior section, there are no source code changes necessary for
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creating the stored map objects.
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</p>
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<a id="entity_sampleviews2"></a>
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<pre class="programlisting">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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partMap =
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new StoredSortedMap(db.getPartDatabase(),
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partKeyBinding, partDataBinding, true);
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supplierMap =
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new StoredSortedMap(db.getSupplierDatabase(),
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supplierKeyBinding, supplierDataBinding, true);
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shipmentMap =
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new StoredSortedMap(db.getShipmentDatabase(),
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shipmentKeyBinding, shipmentDataBinding, true);
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...
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} </pre>
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<p>
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Specifying an
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<a class="ulink" href="../../java/com/sleepycat/bind/EntityBinding.html" target="_top">EntityBinding</a>
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will select a different
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<a class="ulink" href="../../java/com/sleepycat/collections/StoredMap.html" target="_top">StoredSortedMap</a>
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constructor, but the syntax is the same. In general, an entity
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binding may be used anywhere that a value binding is used.
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</p>
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<p>
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The following getter methods are defined for use by other
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classes in the example program. Instead of returning the map's
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entry set
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(<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Map.html#entrySet()" target="_top">Map.entrySet</a>),
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the map's value set
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(<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Map.html#values()" target="_top">Map.values</a>)
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is returned. The entry set was convenient in prior examples because
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it allowed enumerating all key/value pairs in the collection. Since
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an entity contains the key and the value, enumerating the value set
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can now be used more conveniently for the same purpose.
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</p>
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<a id="entity_sampleviews3"></a>
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<pre class="programlisting"><strong class="userinput"><code>import com.sleepycat.collections.StoredValueSet;</code></strong>
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...
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public class SampleViews
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{
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...
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<strong class="userinput"><code> public StoredValueSet getPartSet()
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{
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return (StoredValueSet) partMap.values();
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}
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public StoredValueSet getSupplierSet()
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{
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return (StoredValueSet) supplierMap.values();
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}
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public StoredValueSet getShipmentSet()
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{
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return (StoredValueSet) shipmentMap.values();
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}</code></strong>
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...
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} </pre>
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<p>
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Notice that the collection returned by the
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<a class="ulink" href="../../java/com/sleepycat/collections/StoredMap.html#values()" target="_top">StoredSortedMap.values</a>
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method is actually a
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<a class="ulink" href="../../java/com/sleepycat/collections/StoredValueSet.html" target="_top">StoredValueSet</a>
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and not just a
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<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Collection.html" target="_top">Collection</a>
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as defined by the
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<a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/Map.html#values()" target="_top">Map.values</a>
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interface. As long as duplicate keys are not allowed, this
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collection will behave as a true set and will disallow the addition
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of duplicates, etc.
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</p>
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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="creatingentitybindings.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="Entity.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="entitieswithcollections.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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Creating Entity Bindings
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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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Using Entities with Collections
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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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