Catching exception/error in database transaction

Question

I am using the following way in joomla 2.5 and 3 to execute database query -

$database = JFactory::getDBO();
$database->setQuery
$database->execute();

but how do I catch errors/exceptions if the query fails for any reasons as $database->getErrorNum() is deprecated?

Answer 1

JError has been deprecated in J3.x, in favour of PHP exceptions, as it intermixed 2 different programming concepts: logging and error handling (the logging side has now been implemented as JLog).

For your exact case, you can wrap your code in a try / catch block to get the error, as shown in this SO answer:

try {
    ...
    $db->setQuery($query);
    $result = $db->loadResult();
}
catch (Exception $e){
    echo $e->getMessage();
}

Note that $database->execute() is stated to NOT work in J2.5. You should use $database->query() if you need an equivalent.

In Joomla 2.5 and 3.x the JDatabase object methods updateRecord() and insertRecord() also throw errors you can catch if they fail:

try {
    JFactory::getDbo()->updateObject('#_table_name', $data);
} catch (Exception $e) {
    //...handle the exception
}

If you're developing for Joomla 3.x only, you can also use a try catch block with SQL transactions to get the error details:

$db = JFactory::getDbo();

try {
    $db->transactionStart();

    $query = $db->getQuery(true);

    $values = array($db->quote('TEST_CONSTANT'), $db->quote('Custom'), $db->quote('/path/to/translation.ini'));

    $query->insert($db->quoteName('#__overrider'));
    $query->columns($db->quoteName(array('constant', 'string', 'file')));
    $query->values(implode(',',$values));

    $db->setQuery($query);
    $result = $db->execute();

    $db->transactionCommit();
}
catch (Exception $e) {
    // catch any database errors.
    $db->transactionRollback();
    JErrorPage::render($e);
}

Answer 2

Ideally install pecl then extend the appropriate JDatabase* class and override JFactory::getDbo() with an implementation of the below to eliminate the need for a squillion code updates to wrap every critical db query in try catch statements.

Next best thing for me is the below support for the old way and the new way:

Include this somewhere

class jDbUtils
{
    protected static $dbErrorMessage = '';

    public static function stupidJ3CatchDatabaseExecute($db, $cmd, $report = false) {
        self::$dbErrorMessage = '';
        try {
            $res = $db->$cmd();
            // legacy db error support
            if (method_exists($db, 'getErrorNum') && $db->getErrorNum())
                throw new Exception($db->getErrorMsg());
            return $res;
        } catch(Exception $e) {
            self::$dbErrorMessage = $e->getMessage();
            if ($report)
                self::reportIfDbError();
            return false;
        }
    }

    public static function reportIfDbError()
    {
        if (self::$dbErrorMessage) {
            JFactory::getApplication()->enqueueMessage(self::$dbErrorMessage, 'error');
            return true;
        }
    }
}

Then use it like this

function someDbInteraction(){
    $db = JFactory::getDbo();
    $db->setQuery('SELECT no_such_col FROM no_such_table LIMIT 1');
    $res = jDbUtils::stupidJ3CatchDatabaseExecute($db, 'loadResult');
    if (jDbUtils::reportIfDbError())
        return false;
    // do more processing
    return $res;
}