Sindbad~EG File Manager
<?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>Java programming notes</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 Programmer's Reference Guide" />
<link rel="up" href="java.html" title="Chapter 5. Java API" />
<link rel="prev" href="java_compat.html" title="Compatibility" />
<link rel="next" href="java_faq.html" title="Java FAQ" />
</head>
<body>
<div xmlns="" class="navheader">
<div class="libver">
<p>Library Version 18.1.40</p>
</div>
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">Java programming notes</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="java_compat.html">Prev</a> </td>
<th width="60%" align="center">Chapter 5. Java API </th>
<td width="20%" align="right"> <a accesskey="n" href="java_faq.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="java_program"></a>Java programming notes</h2>
</div>
</div>
</div>
<p>
Although the Java API parallels the Berkeley DB C++/C
interface in many ways, it differs where the Java language
requires. For example, the handle method names are camel-cased
and conform to Java naming patterns. (The C++/C method names
are currently provided, but are deprecated.)
</p>
<div class="orderedlist">
<ol type="1">
<li>
The Java runtime does not automatically close
Berkeley DB objects on finalization. There are several
reasons for this. One is that finalization is generally
run only when garbage collection occurs, and there is no
guarantee that this occurs at all, even on exit. Allowing
specific Berkeley DB actions to occur in ways that cannot
be replicated seems wrong. Second, finalization of objects
may happen in an arbitrary order, so we would have to do
extra bookkeeping to make sure that everything was closed
in the proper order. The best word of advice is to always
do a close() for any matching open() call. Specifically,
the Berkeley DB package requires that you explicitly call
close on each individual <a class="ulink" href="../java/com/sleepycat/db/Database.html" target="_top">Database</a> and <a class="ulink" href="../java/com/sleepycat/db/Cursor.html" target="_top">Cursor</a> object
that you opened. Your database
activity may not be synchronized to disk unless you do
so.
</li>
<li>
Some methods in the Java API have no return type,
and throw a <a class="ulink" href="../java/com/sleepycat/db/DatabaseException.html" target="_top">DatabaseException</a>
when an severe error
arises. There are some notable methods that do have a
return value, and can also throw an exception. The "get"
methods in <a class="ulink" href="../java/com/sleepycat/db/Database.html" target="_top">Database</a> and <a class="ulink" href="../java/com/sleepycat/db/Cursor.html" target="_top">Cursor</a> both
return 0 when a get succeeds,
<a class="link" href="program_errorret.html#program_errorret.DB_NOTFOUND">DB_NOTFOUND</a>
when the key is not found, and throw an error when there is a severe
error. This approach allows the programmer to check for typical data-driven
errors by watching return values without special casing
exceptions.
<p>
An object of type <a class="ulink" href="../java/com/sleepycat/db/MemoryException.html" target="_top">
MemoryException</a> is thrown when a Dbt is
too small to hold the corresponding key or data
item.
</p><p>
An object of type <a class="ulink" href="../java/com/sleepycat/db/DeadlockException.html" target="_top">
DeadlockException</a> is thrown when a
deadlock would occur.
</p><p>
An object of type <a class="ulink" href="../java/com/sleepycat/db/RunRecoveryException.html" target="_top">
RunRecoveryException</a>, a subclass of
<a class="ulink" href="../java/com/sleepycat/db/DatabaseException.html" target="_top">
DatabaseException</a>, is thrown when there
is an error that requires a recovery of the database
using <a href="../api_reference/C/db_recover.html" class="olink">db_recover</a> utility.
</p><p>
An object of type <a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/lang/IllegalArgumentException.html" target="_top">
IllegalArgumentException</a> a standard Java
Language exception, is thrown when there is an error
in method arguments.</p><p>
An object of type <a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/lang/OutOfMemoryError.html" target="_top">
OutOfMemoryError</a> is thrown when the
system cannot provide enough memory to complete the
operation (the ENOMEM system error on
UNIX).
</p></li>
<li>
If there are embedded nulls in the <span class="bold"><strong>curslist</strong></span> argument for <a class="ulink" href="../java/com/sleepycat/db/Database.html#join(com.sleepycat.db.Cursor[], com.sleepycat.db.JoinConfig)" target="_top">
Database.join(com.sleepycat.db.Cursor[],
com.sleepycat.db.JoinConfig)</a>, they will be
treated as the end of the list of cursors, even if you may
have allocated a longer array. Fill in all the cursors in
your array unless you intend to cut it short.
</li>
<li>
If you are using custom class loaders in your
application, make sure that the Berkeley DB classes are
loaded by the system class loader, not a custom class
loader. This is due to a JVM bug that can cause an access
violation during finalization (see the bug 4238486 in Sun
Microsystem's Java Bug Database).
</li>
</ol>
</div>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="java_compat.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="java.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="java_faq.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">Compatibility </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> Java FAQ</td>
</tr>
</table>
</div>
</body>
</html>
Sindbad File Manager Version 1.0, Coded By Sindbad EG ~ The Terrorists