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168 lines
6 KiB
HTML
168 lines
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>Opening and Closing Databases</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="BasicProgram.html" title="Chapter 2. The Basic Program" />
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<link rel="prev" href="openclasscatalog.html" title="Opening and Closing the Class Catalog" />
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<link rel="next" href="createbindingscollections.html" title="Creating Bindings and 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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Opening and Closing Databases
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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="openclasscatalog.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 2.
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The Basic Program
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="createbindingscollections.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="opendatabases"></a>
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Opening and Closing Databases
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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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This section describes how to open and close the Part, Supplier
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and Shipment databases. A <span class="emphasis"><em>database</em></span> is a collection of
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records, each of which has a key and a value. The keys and values
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are stored in a selected format, which defines the syntax of the
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stored data. Two examples of formats are Java serialization format
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and tuple format. In a given database, all keys have the same
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format and all values have the same format.
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</p>
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<p>
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The <code class="classname">SampleDatabase</code> class is extended to open and close
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the three databases. The following additional class members are
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needed.
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</p>
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<a id="cb_sampledatabase3"></a>
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<pre class="programlisting">public class SampleDatabase
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{
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...
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<strong class="userinput"><code> private static final String SUPPLIER_STORE = "supplier_store";
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private static final String PART_STORE = "part_store";
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private static final String SHIPMENT_STORE = "shipment_store";</code></strong>
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...
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<strong class="userinput"><code> private Database supplierDb;
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private Database partDb;
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private Database shipmentDb;</code></strong>
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...
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} </pre>
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<p>
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For each database there is a database name constant and a
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<code class="classname">Database</code> object.
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</p>
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<p>
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The following statements open the three databases by
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constructing a <code class="classname">Database</code> object.
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</p>
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<a id="cb_je_sampledatabase4"></a>
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<pre class="programlisting"> public SampleDatabase(String homeDirectory)
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throws DatabaseException, FileNotFoundException
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{
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...
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DatabaseConfig dbConfig = new DatabaseConfig();
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dbConfig.setTransactional(true);
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dbConfig.setAllowCreate(true);
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...
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<strong class="userinput"><code> partDb = env.openDatabase(null, PART_STORE, dbConfig);
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supplierDb = env.openDatabase(null, SUPPLIER_STORE, dbConfig);
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shipmentDb = env.openDatabase(null, SHIPMENT_STORE, dbConfig);</code></strong>
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...
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} </pre>
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<p>
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The database configuration object that was used previously for
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opening the catalog database is reused for opening the three
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databases above. The databases are created if they don't already
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exist. The parameters of the <code class="methodname">openDatabase()</code> method were
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described earlier when the class catalog database was opened.
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</p>
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<p>
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The following statements close the three databases.
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</p>
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<a id="cb_close2"></a>
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<pre class="programlisting"> public void close()
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throws DatabaseException
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{
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<strong class="userinput"><code> partDb.close();
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supplierDb.close();
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shipmentDb.close();</code></strong>
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javaCatalog.close();
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env.close();
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} </pre>
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<p>
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It is recommended that all databases, including the catalog database, is closed
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before closing the environment.
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</p>
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<p>
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The following getter methods return the databases for use by
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other classes in the example program.
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</p>
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<a id="cb_sampledatabase_getters"></a>
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<pre class="programlisting">public class SampleDatabase
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{
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...
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<strong class="userinput"><code> public final Database getPartDatabase()
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{
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return partDb;
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}
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public final Database getSupplierDatabase()
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{
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return supplierDb;
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}
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public final Database getShipmentDatabase()
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{
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return shipmentDb;
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}</code></strong>
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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="openclasscatalog.html">Prev</a> </td>
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||
<td width="20%" align="center">
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<a accesskey="u" href="BasicProgram.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="createbindingscollections.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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Opening and Closing the Class Catalog
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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 Bindings and 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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