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HTML
87 lines
4.1 KiB
HTML
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<?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>C++ exceptions</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 Upgrade Guide" />
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<link rel="up" href="upgrade_4_1_toc.html" title="Chapter 9. Upgrading Berkeley DB 4.0 applications to Berkeley DB 4.1" />
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<link rel="prev" href="upgrade_4_1_java.html" title="Java exceptions" />
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<link rel="next" href="upgrade_4_1_app_dispatch.html" title="Application-specific logging and recovery" />
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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 11.2.5.2</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">C++ exceptions</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="upgrade_4_1_java.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 9. Upgrading Berkeley DB 4.0 applications to Berkeley DB 4.1</th>
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<td width="20%" align="right"> <a accesskey="n" href="upgrade_4_1_app_dispatch.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="upgrade_4_1_cxx"></a>C++ exceptions</h2>
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</div>
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</div>
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</div>
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<p>With default flags, the C++ <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a> and <a href="../api_reference/CXX/db.html" class="olink">Db</a> classes
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can throw exceptions from their constructors. For example, this can
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happen if invalid parameters are passed in or the underlying C
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structures could not be created. If the objects are created in an
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environment that is not configured for exceptions (that is, the
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<a href="../api_reference/CXX/envcreate.html#env_DB_CXX_NO_EXCEPTIONS" class="olink">DB_CXX_NO_EXCEPTIONS</a> flag is specified), errors from the
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constructor will be returned when the handle's open method is called.</p>
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<p>In addition, the behavior of the <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a> and <a href="../api_reference/CXX/db.html" class="olink">Db</a>
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destructors has changed to simplify exception handling in applications.
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The destructors will now close the handle if the handle's close method
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was not called prior to the object being destroyed. The return value
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of the call is discarded, and no exceptions will be thrown.
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Applications should call the close method in normal situations so any
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errors while closing can be handled by the application.</p>
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<p>This change allows applications to be structured as follows:</p>
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<pre class="programlisting">try {
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DbEnv env(0);
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env.open(/* ... */);
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Db db(&env, 0);
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db.open(/* ... */);
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/* ... */
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db.close(0);
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env.close(0);
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} catch (DbException &dbe) {
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// Handle the exception, the handles have already been closed.
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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="upgrade_4_1_java.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="upgrade_4_1_toc.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="upgrade_4_1_app_dispatch.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 exceptions </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"> Application-specific logging and recovery</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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