Checking for duplicate keys with Doctrine 2

You can catch the UniqueConstraintViolationException as such:

use Doctrine\DBAL\Exception\UniqueConstraintViolationException;

// ...

try {
   // ...
   $em->flush();
}
catch (UniqueConstraintViolationException $e) {
    // ....
}

I use this strategy to check for unique constraints after flush(), may not be what you want, but might help someone else.

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When you call flush(), if a unique constrain fails, a PDOException is thrown with the code 23000.

try {
    // ...
    $em->flush();
}
catch( \PDOException $e )
{
    if( $e->getCode() === '23000' )
    {
        echo $e->getMessage();

        // Will output an SQLSTATE[23000] message, similar to:
        // Integrity constraint violation: 1062 Duplicate entry 'x'
        // ... for key 'UNIQ_BB4A8E30E7927C74'
    }

    else throw $e;
}

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If you need to get the name of the failing column:

Create table indices with prefixed names, eg. 'unique_'

 * @Entity
 * @Table(name="table_name",
 *      uniqueConstraints={
 *          @UniqueConstraint(name="unique_name",columns={"name"}),
 *          @UniqueConstraint(name="unique_email",columns={"email"})
 *      })

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DO NOT specify your columns as unique in the @Column definition

This seems to override the index name with a random one...

 **ie.** Do not have 'unique=true' in your @Column definition

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After you regenerate your table (you may need to drop it & rebuild), you should be able to extract the column name from the exception message.

// ...
if( $e->getCode() === '23000' )
{
    if( \preg_match( "%key 'unique_(?P<key>.+)'%", $e->getMessage(), $match ) )
    {
        echo 'Unique constraint failed for key "' . $match[ 'key' ] . '"';
    }

    else throw $e;
}

else throw $e;

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Not perfect, but it works...