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<title>Berkeley DB Reference Guide: Opening and closing the class catalog</title>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Java API Tutorial - Basic</dl></h3></td>
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<p>
<h3 align=center>Opening and closing the class catalog</h3>
<p>This section describes how to open and close the Java class catalog. The
class catalog is a specialized database store that contains the Java class
descriptions of the serialized objects that are stored in the database. The
class descriptions are stored in the catalog rather than storing them
redundantly in each database record. A single class catalog per environment
must be opened whenever serialized objects will be stored in the database.</p>
<hr size=1 noshade>
<p>The <b>SampleDatabase</b> class is extended to open and close the
class catalog. The following additional imports and class members are
needed.</p>
<blockquote><pre>
<b>import com.sleepycat.bdb.StoredClassCatalog;
</b>...
public class SampleDatabase
{
<b> private static final String CLASS_CATALOG = "java_class_catalog";
</b> ...
<b> private StoredClassCatalog javaCatalog;
</b> ...
}
</pre></blockquote>
<p>While the class catalog is a database store, it contains metadata for
other stores and is therefore treated specially by the Java API. The
<a href="../../java/com/sleepycat/bdb/StoredClassCatalog.html">StoredClassCatalog</a>
class encapsulates the
catalog store and implements this special behavior.</p>
<hr size=1 noshade>
<p>The following statements open the class catalog by creating a
StoredClassCatalog object. The catalog file is created if it doesn't already
exist.</p>
<blockquote><pre>
public SampleDatabase(String homeDirectory, boolean runRecovery)
throws DbException, FileNotFoundException
{
...
<b> int flags = Db.DB_CREATE | Db.DB_AUTO_COMMIT;
javaCatalog = new StoredClassCatalog(env, CLASS_CATALOG, null, flags);
</b> }
</pre></blockquote>
<p>The environment parameter is specified when opening any store, since a
store always operates within a single environment.</p>
<p>The two String parameters are also used when opening any store. They
specify the filename and database (sub-file) name, of the store. The database
(sub-file) name is optional, and is null in the example.</p>
<p>The <b>flags</b> variable is initialized with
<a href="../../java/com/sleepycat/db/Db.html#DB_CREATE">Db.DB_CREATE</a>
to create the file if it
doesn't exist and with
<a href="../../java/com/sleepycat/db/Db.html#DB_AUTO_COMMIT">Db.DB_AUTO_COMMIT</a>
to
create the store within an implicit transaction. These flags are used for
opening all stores in the example.</p>
<hr size=1 noshade>
<p>The following statement closes the class catalog.</p>
<blockquote><pre>
public void close()
throws DbException, IOException
{
<b> javaCatalog.close();
</b> env.close(0);
}
</pre></blockquote>
<p>The catalog store, and all other stores, must be closed before closing
the environment.</p>
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