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