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diff --git a/db/docs/ref/bdb_basic/views.html b/db/docs/ref/bdb_basic/views.html deleted file mode 100644 index 7294d6e35..000000000 --- a/db/docs/ref/bdb_basic/views.html +++ /dev/null @@ -1,183 +0,0 @@ -<!--$Id: views.html,v 1.1 2003/12/15 21:43:45 jbj Exp $--> -<!--Copyright 1997-2003 by Sleepycat Software, Inc.--> -<!--All rights reserved.--> -<!--See the file LICENSE for redistribution information.--> -<html> -<head> -<title>Berkeley DB Reference Guide: Creating bindings and collections</title> -<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> -<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> -</head> -<body bgcolor=white> -<a name="2"><!--meow--></a> -<table width="100%"><tr valign=top> -<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Java API Tutorial - Basic</dl></h3></td> -<td align=right><a href="../bdb_basic/stores.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../bdb_basic/main.html"><img src="../../images/next.gif" alt="Next"></a> -</td></tr></table> -<p> -<h3 align=center>Creating bindings and collections</h3> -<p><i>Bindings</i> convert between stored records and Java objects. In -this example, Java serialization bindings are used. Serial bindings are the -simplest type of bindings because no mapping of fields or type conversion is -needed. Tuple bindings, which are more difficult to create than serial -bindings but have some advantages, will be introduced later in the Tuple -example program.</p> -<p>Standard Java <i>collections</i> are used to access records in a -database store. Stored collections use bindings transparently to convert -the records to objects when they are retrieved from the collection, and to -convert the objects to records when they are stored in the collection.</p> -<p>An important characteristic of stored collections is that they do -<i>not</i> perform object caching. Every time an object is accessed via a -collection it will be added to or retrieved from the store, and the bindings -will be invoked to convert the data. Objects are therefore always passed and -returned by value, not by reference. Because Berkeley DB is an embedded database, -efficient caching of stored records is performed by the database library.</p> -<hr size=1 noshade> -<p>The <b>SampleViews</b> class is used to create the bindings and -collections. This class is separate from the <b>SampleDatabase</b> class to -illustrate the idea that a single set of stored data can be accessed via -multiple bindings and collections, or <i>views</i>. The skeleton for the -<b>SampleViews</b> class follows.</p> -<blockquote><pre><b>import com.sleepycat.bdb.bind.DataBinding; -import com.sleepycat.bdb.bind.serial.SerialBinding; -import com.sleepycat.bdb.collection.StoredEntrySet; -import com.sleepycat.bdb.collection.StoredMap; -<p> -public class SampleViews -{ - private StoredMap partMap; - private StoredMap supplierMap; - private StoredMap shipmentMap; -<p> - public SampleViews(SampleDatabase db) - { - } -} -</b></pre></blockquote> -<p>A -<a href="../../java/com/sleepycat/bdb/collection/StoredMap.html">StoredMap</a> - field is used -for each store. The StoredMap class implements the standard Java -<a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.html">Map</a> - interface, which has methods for obtaining a -<a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Set.html">Set</a> - of keys, a -<a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Collection.html">Collection</a> - of values, or a -<a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Set.html">Set</a> - of -<a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.Entry.html">Map.Entry</a> - key/value pairs. -Because stores contain key/value pairs, any Berkeley DB store may be represented as a -Java map.</p> -<hr size=1 noshade> -<p>The following statements create the bindings using the -<a href="../../java/com/sleepycat/bdb/bind/serial/SerialBinding.html">SerialBinding</a> - class.</p> -<blockquote><pre> - public SampleViews(SampleDatabase db) - { -<b> DataBinding partKeyBinding = new SerialBinding(db.getPartKeyFormat()); - DataBinding partValueBinding = new SerialBinding(db.getPartValueFormat()); - DataBinding supplierKeyBinding = new SerialBinding(db.getSupplierKeyFormat()); - DataBinding supplierValueBinding = new SerialBinding(db.getSupplierValueFormat()); - DataBinding shipmentKeyBinding = new SerialBinding(db.getShipmentKeyFormat()); - DataBinding shipmentValueBinding = new SerialBinding(db.getShipmentValueFormat()); -</b> } -</pre></blockquote> -<p>A serial binding is created from a serial format. The reader may wonder -why a binding is needed at all, since the format contains all the information -needed to perform Java serialization. In fact, the serial bindings used here -add very little value to the serial format.</p> -<p>Bindings are distinct from formats because a single format can be used -with multiple bindings. With serial bindings, an example is a specialized -binding that extracts a single field from the stored object and returns that -field only. Another example is a binding that converts the stored object to an -instance of a different class. These are examples of how bindings can provide -multiple views of the same data.</p> -<hr size=1 noshade> -<p>The following statements create standard Java maps using the -<a href="../../java/com/sleepycat/bdb/collection/StoredMap.html">StoredMap</a> - class.</p> -<blockquote><pre> - public SampleViews(SampleDatabase db) - { -<b> partMap = - new StoredMap(db.getPartStore(), - partKeyBinding, partValueBinding, true); - supplierMap = - new StoredMap(db.getSupplierStore(), - supplierKeyBinding, supplierValueBinding, true); - shipmentMap = - new StoredMap(db.getShipmentStore(), - shipmentKeyBinding, shipmentValueBinding, true); -</b> } -</pre></blockquote> -<p>The first parameter of the -<a href="../../java/com/sleepycat/bdb/collection/StoredMap.html">StoredMap</a> - constructor is the store. Creating a map from a store will use the -store keys (the primary keys) as the map keys. The Index example shows how -to use index keys as map keys.</p> -<p>The second and third parameters are the key and value bindings to use -when storing and retrieving objects via the map.</p> -<p>The fourth and last parameter specifies whether changes will be allowed -via the collection. If false is passed, the collection will be read-only.</p> -<hr size=1 noshade> -<p>The following getter methods return the stored maps for use by other -classes in the example program. Convenience methods for returning entry sets -are also included.</p> -<blockquote><pre> -public class SampleViews -{ - ... -<b> public final StoredMap getPartMap() - { - return partMap; - } -<p> - public final StoredMap getSupplierMap() - { - return supplierMap; - } -<p> - public final StoredMap getShipmentMap() - { - return shipmentMap; - } -<p> - public final StoredEntrySet getPartEntrySet() - { - return (StoredEntrySet) partMap.entrySet(); - } -<p> - public final StoredEntrySet getSupplierEntrySet() - { - return (StoredEntrySet) supplierMap.entrySet(); - } -<p> - public final StoredEntrySet getShipmentEntrySet() - { - return (StoredEntrySet) shipmentMap.entrySet(); - } -</b> ... -} -</pre></blockquote> -<p>Note that StoredMap and StoredEntrySet are returned rather than just -returning Map and Set. Since StoredMap implements the Map interface and -StoredEntrySet implements the Set interface, you may ask why Map and Set were -not returned directly.</p> -<p>StoredMap, StoredEntrySet, and other stored collection classes have a -small number of extra methods beyond those in the Java collection interfaces. -The stored collection types are therefore returned to avoid casting when using -the extended methods. Normally, however, only a Map or Set is needed, and may -be used as follows.</p> -<blockquote><pre> -<b> SampleViews views = ... - Map partMap = views.getPartMap(); - Set supplierEntries = views.getSupplierEntrySet(); -</b></pre></blockquote> -<table width="100%"><tr><td><br></td><td align=right><a href="../bdb_basic/stores.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../bdb_basic/main.html"><img src="../../images/next.gif" alt="Next"></a> -</td></tr></table> -<p><font size=1><a href="../../sleepycat/legal.html">Copyright (c) 1996-2003</a> <a href="http://www.sleepycat.com">Sleepycat Software, Inc.</a> - All rights reserved.</font> -</body> -</html> |