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<title>DBException</title>
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<p><font size="6" face="Bookman Old Style"><em><strong><u>dtl</u></strong></em></font></p>
<p><img src="stat.gif" width="6" height="6"> <!--end header--> <br>
</p>
<h1>DBException</h1>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td><img src="exceptions.gif" width="194" height="38"></td>
<td align="right"><img src="type.gif" width="194"
height="39"></td>
</tr>
<tr>
<td valign="top"><b>Category</b>: exceptions</td>
<td align="right" valign="top"><b>Component type</b>:
type</td>
</tr>
</table>
<h3>Description</h3>
<p><tt>DBException </tt>is thrown when one of the database
specific classes such as <font size="2" face="Courier New">DBView</font>
or <font size="2" face="Courier New">DBStmt</font> encounters an
error. An exception of this type stores strings representing
which method the exception was thrown in and a message describing
what error occurred. <tt>DBException </tt>also captures a vector
of SQL errors (if any) that occurred to trigger this exception.
The call to the constructor initializes these constructs (see
below). The user can extract a stringified message with all of
this information from the exception using the standard <font
size="2" face="Courier New">what() </font><font size="3">method.</font></p>
<h3>Definition</h3>
<p>Defined in the <font size="2" face="Courier New">DBException.h</font><font
size="1" face="Courier New"> </font>header file. </p>
<h3>Example: Throwing and catching a DBException ... executing an
invalid query directly using a DBStmt object</h3>
<p><code>void IWillThrow()<br>
{<br>
DBStmt("THIS SQL QUERY WON'T EXECUTE").Execute();
<span class="codeComment">// this *definitely* will throw DBException<br>
//
will print out ODBC msg. specifying this blatant syntax error!</span><br>
}<br>
<br>
int main()<br>
{<br>
try<br>
{<br>
DBConnection::GetDefaultConnection.Connect("UID=example;PWD=example;DSN=example");<br>
<br>
<span class="codeComment">// call our method which
throws</span><br>
IWillThrow();<br>
}<br>
catch (RootException &ex)<br>
{<br>
/<span class="codeComment">/ can also say: cout
<< ex << endl;</span><br>
<span class="codeComment">// operator<<() for
RootExceptions just streams out what()</span><br>
cout << ex.what()
<< endl;<br>
}<br>
return 0; <span class="codeComment">// won't reach here ... exception
thrown above</span><br>
}</code></p>
<h3>Model of</h3>
<p>Standard C++ library exception.</p>
<h3>Public base classes</h3>
<p><font size="2" face="Courier New">RootException</font></p>
<h3>Members</h3>
<table border="2">
<tr>
<th>Member </th>
<th>Where defined </th>
<th>Description </th>
</tr>
<tr>
<td valign="top"><font size="2" face="Courier New">DBException(const
string &meth, const string &msg, DBConnection *conn,
DBStmt *stmt)</font></td>
<td valign="top"><tt>DBException</tt></td>
<td valign="top">Constructor which takes a specific
method indicating where exception is being thrown, an
error message describing the problem encountered, and
pointers to the <font size="2" face="Courier New">DBConnection
</font>and <font size="2" face="Courier New">DBStmt </font>objects
being used in the operation that threw or <font size="2"
face="Courier New">NULL </font>using the following
convention: <ul>
<li>If the exception occurred due to a bad API call
and involved no actual accesses to the database,
pass <font size="2" face="Courier New">NULL </font>for
both pointers.</li>
<li>If the exception occurred due to a bad ODBC call
(thus accesses to the database were bad) and
involved a <font size="2" face="Courier New">DBConnection
connxn, </font>but no associated <font size="2"
face="Courier New">DBStmt, </font>pass in <font
size="2" face="Courier New">&connxn</font>
for the <font size="2" face="Courier New">conn</font>
parameter and <font size="2" face="Courier New">NULL</font>
for <font size="2" face="Courier New">stmt</font>.</li>
<li>If the exception occurred due to a bad ODBC call
(thus accesses to the database were bad) and
involved a <font size="2" face="Courier New">DBStmt
statement, </font><font size="3">remember that
there is an associated </font><font size="2"
face="Courier New">DBConnection </font><font
size="3">with that</font><font size="2"
face="Courier New"> DBStmt, </font><font size="3">accessible
by calling </font><font size="2"
face="Courier New">statement.GetConnection(). </font><font
size="3">So in this case, pass in </font><font
size="2" face="Courier New">&(statement.GetConnection())
</font>for the <font size="2" face="Courier New">conn</font>
parameter and <font size="2" face="Courier New">&statement</font>
for <font size="2" face="Courier New">stmt</font>.</li>
</ul>
<p>The constructor calls a private method <font size="2"
face="Courier New">ShowSQLErrors() </font>to generate the
vector of any SQL errors that triggered this exception if
either pointer is non-<font size="2" face="Courier New">NULL.</font></p>
</td>
</tr>
<tr>
<td valign="top"><font size="2" face="Courier New">virtual
const char* what() const throw()</font></td>
<td valign="top"><tt>DBException</tt> </td>
<td valign="top">Overrides behavior in <font size="2"
face="Courier New">RootException. </font><font size="3">Returns
a C string describing the exception, including the method
it was thrown in, the error message describing why it was
thrown, any SQL errors that led to the exception being
thrown, and what type of exception was thrown. Subclasses
do and may override </font><font size="2"
face="Courier New">what() </font>based on their needs. <font
size="3">See Note </font><a href="RootException.htm#1"><font
size="3">[1]</font></a><font size="3"> in </font><a
href="RootException.htm"><tt>RootException</tt></a><font
size="3">.</font></td>
</tr>
<tr>
<td valign="top"><tt>friend ostream &operator<<(ostream
&o, const RootException &ex)</tt></td>
<td valign="top"><tt>RootException</tt> </td>
<td valign="top">Note that this is a friend function, and
not a member. Streams out <font size="2"
face="Courier New">ex.what()</font><font size="3"> to </font><font
size="2" face="Courier New">o.</font><font size="3"> As </font><font
size="2" face="Courier New">what() </font><font size="3">is
virtual, the appropriate version of that method will be
called for </font><font size="2" face="Courier New">ex.</font></td>
</tr>
<tr>
<td valign="top"><tt>pair<string, string>
GetODBCError()</tt></td>
<td valign="top"><tt>DBException</tt> </td>
<td valign="top">Prints out a pair containing strings indicating
the SQL state and description
of the ODBC error that caused this exception to be thrown.</td>
</tr>
</table>
<h3>Notes</h3>
<p>None.</p>
<h3>See also</h3>
<p><a href="RootException.htm"><tt>RootException</tt></a>.<br>
<br>
</p>
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