mirror of
https://github.com/berkeleydb/je.git
synced 2024-11-20 11:16:25 +00:00
254 lines
9.1 KiB
HTML
254 lines
9.1 KiB
HTML
|
<?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>Implementing the Main Program</title>
|
|||
|
|
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
|||
|
|
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
|
|||
|
|
<link rel="start" href="index.html" title="Berkeley DB Java Edition Collections Tutorial" />
|
|||
|
|
<link rel="up" href="BasicProgram.html" title="Chapter 2. The Basic Program" />
|
|||
|
|
<link rel="prev" href="createbindingscollections.html" title="Creating Bindings and Collections" />
|
|||
|
|
<link rel="next" href="usingtransactions.html" title="Using Transactions" />
|
|||
|
|
</head>
|
|||
|
|
<body>
|
|||
|
|
<div xmlns="" class="navheader">
|
|||
|
|
<div class="libver">
|
|||
|
|
<p>Library Version 12.2.7.5</p>
|
|||
|
|
</div>
|
|||
|
|
<table width="100%" summary="Navigation header">
|
|||
|
|
<tr>
|
|||
|
|
<th colspan="3" align="center">
|
|||
|
|
Implementing the Main Program
|
|||
|
|
</th>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="20%" align="left"><a accesskey="p" href="createbindingscollections.html">Prev</a> </td>
|
|||
|
|
<th width="60%" align="center">Chapter 2.
|
|||
|
|
The Basic Program
|
|||
|
|
</th>
|
|||
|
|
<td width="20%" align="right"> <a accesskey="n" href="usingtransactions.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="implementingmain"></a>
|
|||
|
|
Implementing the Main Program
|
|||
|
|
</h2>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
The main program opens the environment and databases, stores and retrieves
|
|||
|
|
objects within a transaction, and finally closes the environment
|
|||
|
|
databases. This section describes the main program shell, and the
|
|||
|
|
next section describes how to run transactions for storing and
|
|||
|
|
retrieving objects.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The <code class="classname">Sample</code> class contains the main program. The skeleton
|
|||
|
|
for the <code class="classname">Sample</code> class follows.
|
|||
|
|
</p>
|
|||
|
|
<a id="cb_je_sample"></a>
|
|||
|
|
<pre class="programlisting"><strong class="userinput"><code>import com.sleepycat.je.DatabaseException;
|
|||
|
|
import java.io.FileNotFoundException;
|
|||
|
|
|
|||
|
|
public class Sample
|
|||
|
|
{
|
|||
|
|
private SampleDatabase db;
|
|||
|
|
private SampleViews views;
|
|||
|
|
|
|||
|
|
public static void main(String args)
|
|||
|
|
{
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
private Sample(String homeDir)
|
|||
|
|
throws DatabaseException, FileNotFoundException
|
|||
|
|
{
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
private void close()
|
|||
|
|
throws DatabaseException
|
|||
|
|
{
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
private void run()
|
|||
|
|
throws Exception
|
|||
|
|
{
|
|||
|
|
}
|
|||
|
|
}</code></strong> </pre>
|
|||
|
|
<p>
|
|||
|
|
The main program uses the <code class="classname">SampleDatabase</code> and
|
|||
|
|
<code class="classname">SampleViews</code> classes that were described in the preceding
|
|||
|
|
sections. The <code class="methodname">main</code> method will create an instance of the
|
|||
|
|
<code class="classname">Sample</code> class, and call its <code class="methodname">run()</code> and <code class="methodname">close()</code>
|
|||
|
|
methods.
|
|||
|
|
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The following statements parse the program's command line
|
|||
|
|
arguments.
|
|||
|
|
</p>
|
|||
|
|
<a id="cb_main"></a>
|
|||
|
|
<pre class="programlisting"> public static void main(String[] args)
|
|||
|
|
{
|
|||
|
|
<strong class="userinput"><code> System.out.println("\nRunning sample: " + Sample.class);
|
|||
|
|
String homeDir = "./tmp";
|
|||
|
|
for (int i = 0; i < args.length; i += 1)
|
|||
|
|
{
|
|||
|
|
String arg = args[i];
|
|||
|
|
if (args[i].equals("-h") && i < args.length - 1)
|
|||
|
|
{
|
|||
|
|
i += 1;
|
|||
|
|
homeDir = args[i];
|
|||
|
|
}
|
|||
|
|
else
|
|||
|
|
{
|
|||
|
|
System.err.println("Usage:\n java " +
|
|||
|
|
Sample.class.getName() +
|
|||
|
|
"\n [-h <home-directory>]");
|
|||
|
|
System.exit(2);
|
|||
|
|
}
|
|||
|
|
}</code></strong>
|
|||
|
|
...
|
|||
|
|
} </pre>
|
|||
|
|
<p>
|
|||
|
|
The usage command is:
|
|||
|
|
</p>
|
|||
|
|
<pre class="programlisting"><strong class="userinput"><code>java com.sleepycat.examples.bdb.shipment.basic.Sample
|
|||
|
|
[-h <home-directory> ]</code></strong> </pre>
|
|||
|
|
<p>
|
|||
|
|
The <code class="literal">-h</code> command is used to set the <code class="filename">homeDir</code>
|
|||
|
|
variable, which will later be passed to the <code class="methodname">SampleDatabase()</code>
|
|||
|
|
constructor. Normally all Berkeley DB programs should provide a way
|
|||
|
|
to configure their database environment home directory.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The default for the home directory is <code class="filename">./tmp</code> — the tmp
|
|||
|
|
subdirectory of the current directory where the sample is run. The
|
|||
|
|
home directory must exist before running the sample. To re-create
|
|||
|
|
the sample database from scratch, delete all files in the home
|
|||
|
|
directory before running the sample.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The home directory was described previously in
|
|||
|
|
<a class="xref" href="opendbenvironment.html" title="Opening and Closing the Database Environment">
|
|||
|
|
Opening and Closing the Database Environment
|
|||
|
|
</a>.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Of course, the command line arguments shown are only examples
|
|||
|
|
and a real-life application may use different techniques for
|
|||
|
|
configuring these options.
|
|||
|
|
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The following statements create an instance of the <code class="classname">Sample</code>
|
|||
|
|
class and call its <code class="methodname">run()</code> and <code class="methodname">close()</code> methods.
|
|||
|
|
</p>
|
|||
|
|
<a id="cb_main2"></a>
|
|||
|
|
<pre class="programlisting"> public static void main(String args)
|
|||
|
|
{
|
|||
|
|
...
|
|||
|
|
<strong class="userinput"><code> Sample sample = null;
|
|||
|
|
try
|
|||
|
|
{
|
|||
|
|
sample = new Sample(homeDir);
|
|||
|
|
sample.run();
|
|||
|
|
}
|
|||
|
|
catch (Exception e)
|
|||
|
|
{
|
|||
|
|
e.printStackTrace();
|
|||
|
|
}
|
|||
|
|
finally
|
|||
|
|
{
|
|||
|
|
if (sample != null)
|
|||
|
|
{
|
|||
|
|
try
|
|||
|
|
{
|
|||
|
|
sample.close();
|
|||
|
|
}
|
|||
|
|
catch (Exception e)
|
|||
|
|
{
|
|||
|
|
System.err.println("Exception during database close:");
|
|||
|
|
e.printStackTrace();
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}</code></strong>
|
|||
|
|
} </pre>
|
|||
|
|
<p>
|
|||
|
|
The <code class="methodname">Sample()</code> constructor will open the environment and
|
|||
|
|
databases, and the <code class="methodname">run()</code> method will run transactions for
|
|||
|
|
storing and retrieving objects. If either of these throws an
|
|||
|
|
exception, then the program was unable to run and should normally
|
|||
|
|
terminate. (Transaction retries are handled at a lower level and
|
|||
|
|
will be described later.) The first <code class="literal">catch</code> statement handles
|
|||
|
|
such exceptions.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The <code class="literal">finally</code> statement is used to call the <code class="methodname">close()</code>
|
|||
|
|
method since an attempt should always be made to close the environment and
|
|||
|
|
databases
|
|||
|
|
cleanly. If an exception is thrown during close and a prior
|
|||
|
|
exception occurred above, then the exception during close is likely
|
|||
|
|
a side effect of the prior exception.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The <code class="methodname">Sample()</code> constructor creates the <code class="literal">SampleDatabase</code>
|
|||
|
|
and <code class="classname">SampleViews</code> objects.
|
|||
|
|
</p>
|
|||
|
|
<a id="cb_sample"></a>
|
|||
|
|
<pre class="programlisting"> private Sample(String homeDir)
|
|||
|
|
throws DatabaseException, FileNotFoundException
|
|||
|
|
{
|
|||
|
|
<strong class="userinput"><code> db = new SampleDatabase(homeDir);
|
|||
|
|
views = new SampleViews(db);</code></strong>
|
|||
|
|
} </pre>
|
|||
|
|
<p>
|
|||
|
|
Recall that creating the <code class="classname">SampleDatabase</code> object will open
|
|||
|
|
the environment and all databases.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
To close the database the <code class="methodname">Sample.close()</code> method simply
|
|||
|
|
calls <code class="methodname">SampleDatabase.close()</code>.
|
|||
|
|
</p>
|
|||
|
|
<a id="cb_sample-close"></a>
|
|||
|
|
<pre class="programlisting"> private void close()
|
|||
|
|
throws DatabaseException
|
|||
|
|
{
|
|||
|
|
<strong class="userinput"><code> db.close();</code></strong>
|
|||
|
|
} </pre>
|
|||
|
|
<p>
|
|||
|
|
The <code class="methodname">run()</code> method is described in the next section.
|
|||
|
|
</p>
|
|||
|
|
</div>
|
|||
|
|
<div class="navfooter">
|
|||
|
|
<hr />
|
|||
|
|
<table width="100%" summary="Navigation footer">
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left"><a accesskey="p" href="createbindingscollections.html">Prev</a> </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="u" href="BasicProgram.html">Up</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right"> <a accesskey="n" href="usingtransactions.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left" valign="top">
|
|||
|
|
Creating Bindings and Collections
|
|||
|
|
</td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="h" href="index.html">Home</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right" valign="top">
|
|||
|
|
Using Transactions
|
|||
|
|
</td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
</div>
|
|||
|
|
</body>
|
|||
|
|
</html>
|