mirror of
https://github.com/yasuhirokimura/db18
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Yasuhiro KIMURA
207 lines
8.7 KiB
HTML
207 lines
8.7 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>Java FAQ</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 Programmer's Reference Guide" />
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<link rel="up" href="java.html" title="Chapter 5. Java API" />
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<link rel="prev" href="java_program.html" title="Java programming notes" />
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<link rel="next" href="bdb_server.html" title="Chapter 6. Berkeley DB Server" />
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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 18.1.25</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">Java FAQ</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="java_program.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 5. Java API </th>
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<td width="20%" align="right"> <a accesskey="n" href="bdb_server.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="java_faq"></a>Java FAQ</h2>
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</div>
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</div>
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</div>
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<div class="orderedlist">
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<ol type="1">
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<li>
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<span class="bold">
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<strong>On what platforms is the Berkeley DB
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Java API supported?</strong>
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</span>
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<p>All platforms supported by Berkeley DB that have a
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JVM compatible with J2SE 1.4 or above.</p>
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</li>
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<li>
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<span class="bold">
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<strong>How does the Berkeley DB Java API
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relate to the J2EE standard?</strong>
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</span>
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<p>
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The Berkeley DB Java API does not currently
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implement any part of the J2EE standard. That said, it
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does implement the implicit standard for Java <a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/guide/collections/" target="_top">
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Java Collections</a>. The concept of a
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transaction exists in several Java packages (J2EE, XA,
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JINI to name a few). Support for these APIs will be
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added based on demand in future versions of Berkeley
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DB.
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</p>
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</li>
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<li>
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<span class="bold">
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<strong>How should I incorporate db.jar and
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the db native library into a Tomcat or other J2EE
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application servers?</strong>
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</span>
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<p>
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Tomcat and other J2EE application servers have the
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ability to rebuild and reload code automatically. When
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using Tomcat this is the case when "reloadable" is set
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to "true". If your WAR file includes the db.jar it too
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will be reloaded each time your code is reloaded. This
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causes exceptions as the native library can't be
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loaded more than once and there is no way to unload
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native code. The solution is to place the db.jar in
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$TOMCAT_HOME/common/lib and let Tomcat load that
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library once at start time rather than putting it into
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the WAR that gets reloaded over and over.
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</p>
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</li>
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<li>
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<span class="bold">
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<strong>Can I use the Berkeley DB Java API
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from within a EJB, a Servlet or a JSP page?</strong>
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</span>
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<p>
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Yes. The Berkeley DB Java API can be used from
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within all the popular J2EE application servers in
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many different ways.
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</p>
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</li>
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<li>
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<span class="bold">
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<strong>During one of the first calls to the
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Berkeley DB Java API, a DbException is thrown with a
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"Bad file number" or "Bad file descriptor"
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message.</strong>
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</span>
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<p>
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There are known large-file support bugs under JNI in
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various releases of the JDK. Please upgrade to the
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latest release of the JDK, and, if that does not solve
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the problem, disable big file support using the
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--disable-largefile configuration option.
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</p>
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</li>
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<li>
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<span class="bold">
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<strong>How can I use native methods from a
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debug build of the Java library?</strong>
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</span>
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<p>
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Set Java's library path so that the debug version of
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Berkeley DB's Java library appears, but the release
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version does not. Berkeley DB tries to load the
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release library first, and if that fails tries the
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debug library.
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</p>
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</li>
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<li>
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<span class="bold">
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<strong>Why is ClassNotFoundException thrown
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when adding a record to the database, when a
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SerialBinding is used?</strong>
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</span>
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<p>
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This problem occurs if you copy the db.jar file into
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the Java extensions (ext) directory. This will cause
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the database code to run under the System class
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loader, and it won't be able to find your application
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classes.
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</p>
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<p>
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You'll have to actually remove db.jar from the Java
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extension directory. If you have more than one
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installation of Java, be sure to remove it from all of
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them. This is necessary even if db.jar is specified in
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the classpath.
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</p>
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<p>
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An example of the exception is:
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</p>
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<pre class="programlisting">collections.ship.basic.SupplierKey
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at java.net.URLClassLoader$1.run(Unknown Source)
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at java.security.AccessController.doPrivileged(Native Method)
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at java.net.URLClassLoader.findClass(Unknown Source)
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at java.lang.ClassLoader.loadClass(Unknown Source)
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at java.lang.ClassLoader.loadClass(Unknown Source)
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at java.lang.ClassLoader.loadClassInternal(Unknown Source)
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at java.lang.Class.forName0(Native Method)
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at java.lang.Class.forName(Unknown Source)
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at com.sleepycat.bind.serial.StoredClassCatalog.
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getClassInfo(StoredClassCatalog.java:211)
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...</pre>
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</li>
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<li>
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<span class="bold">
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<strong>I'm upgrading my Java application to
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Berkeley DB 4.3. Can I use the
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com.sleepycat.db.internal package rather than porting
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my code to the new API?</strong>
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</span>
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<p>
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While it is possible to use the low-level API from
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applications, there are some caveats that should be
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considered when upgrading. The first is that the
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internal API depends on some classes in the public API
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such as DatabaseEntry.
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</p>
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<p>
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In addition, the internal API is closer to the C API
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and doesn't have some of the default settings that
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were part of the earlier Java API. For example,
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applications will need to set the DB_THREAD flag
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explicitly if handles are to be used from multiple
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threads, or subtle errors may occur.
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</p>
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</li>
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</ol>
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</div>
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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="java_program.html">Prev</a> </td>
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||
<td width="20%" align="center">
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<a accesskey="u" href="java.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="bdb_server.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">Java programming notes </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"> Chapter 6. Berkeley DB Server</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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