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HTML
152 lines
6.9 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>Chapter 6. The DbException Class</title>
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<link rel="stylesheet" href="apiReference.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 C++ API Reference" />
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<link rel="up" href="index.html" title="Berkeley DB C++ API Reference" />
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<link rel="prev" href="envversion.html" title="DbEnv::version()" />
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<link rel="next" href="dbdeadlock.html" title="DbDeadlockException" />
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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">Chapter 6. The DbException Class</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="envversion.html">Prev</a> </td>
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<th width="60%" align="center"> </th>
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<td width="20%" align="right"> <a accesskey="n" href="dbdeadlock.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="chapter" 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"><a id="dbexception"></a>Chapter 6. The DbException Class</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db_cxx.h>
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class DbException {
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public:
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int get_errno() const;
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virtual const char *what() const;
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DbEnv *get_env() const;
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}; </pre>
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<p>
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This information describes the <code class="classname">DbException</code> class and how
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it is used by the various Berkeley DB classes.
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</p>
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<p>
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Most methods in the Berkeley DB classes return an <code class="literal">int</code>, but also throw
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an exception. This allows for two different error behaviors. By default, the Berkeley DB
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C++ API is configured to throw an exception whenever a serious error occurs. This
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generally allows for cleaner logic for transaction processing because a try block can
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surround a single transaction. Alternatively, Berkeley DB can be configured to not throw
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exceptions, and instead have the individual function return an error code, by setting
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the <a class="link" href="envcreate.html#env_DB_CXX_NO_EXCEPTIONS">DB_CXX_NO_EXCEPTIONS</a>
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for the <a class="xref" href="dbcreate.html" title="Db">Db</a> and
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<a class="xref" href="envcreate.html" title="DbEnv">DbEnv</a> constructors.
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</p>
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<p>
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A <code class="classname">DbException</code> object contains an informational string, an
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<code class="literal">errno</code>, and a reference to the environment from which the exception
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was thrown. The <code class="literal">errno</code> can be obtained by using the
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<code class="methodname">DbException::get_errno()</code> method, and can be used, in standard
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cases, to determine the type of the exception. The informational string can be obtained
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by using the <code class="methodname">DbException::what()</code>. And, the environment can be
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obtained using the <code class="methodname">DbException::get_env()</code> method.
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</p>
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<p>
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We expect in the future that this class will inherit from the standard class exception,
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but certain language implementation bugs currently prevent this on some platforms.
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</p>
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<p>
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Some methods may return non-zero values without issuing an exception. This occurs in
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situations that are not normally considered an error, but when some informational status
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is returned. For example, the <a class="xref" href="dbget.html" title="Db::get()">Db::get()</a> method returns
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<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
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when a requested key does not appear in the database.
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</p>
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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="exceptionlist"></a>DB C++ Exceptions</h2>
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</div>
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</div>
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</div>
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<div class="navtable">
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<table border="1" width="80%">
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<thead>
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<tr>
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<th>DB C++ Exceptions</th>
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<th>Description</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>
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<a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a>
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</td>
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<td>Exception class for deadlocks</td>
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</tr>
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<tr>
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<td>
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<a class="xref" href="dblocknotgranted.html" title="DbLockNotGrantedException">DbLockNotGrantedException</a>
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</td>
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<td>Exception class for lock request failures</td>
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</tr>
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<tr>
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<td>
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<a class="xref" href="dbmemory.html" title="DbMemoryException">DbMemoryException</a>
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</td>
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<td>Exception class for insufficient memory</td>
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</tr>
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<tr>
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<td>
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<a class="xref" href="dbrephandledead.html" title="DbRepHandleDeadException">DbRepHandleDeadException</a>
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</td>
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<td>Exception class for database and cursor handles that are invalidated in a replicated application. </td>
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</tr>
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<tr>
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<td>
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<a class="xref" href="dbrunrecovery.html" title="DbRunRecoveryException">DbRunRecoveryException</a>
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</td>
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<td>Exception class for failures requiring recovery</td>
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</tr>
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</tbody>
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</table>
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</div>
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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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|
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<tr>
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|
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<td width="40%" align="left"><a accesskey="p" href="envversion.html">Prev</a> </td>
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<td width="20%" align="center"> </td>
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|||
|
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<td width="40%" align="right"> <a accesskey="n" href="dbdeadlock.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">DbEnv::version() </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"> DbDeadlockException</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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