Why does my Perl script fail to connect to the database?

Question

I have a Perl script which retrieves data from MySQL Database. this is the code:

sub startSession{
    my $self = shift;

    my $dsn = "dbi:".$self{platform}.":".$self{database}.":".$self{host}.":".$self{port};
    print "$dsn\n" ;
    $self{dbHandle} = DBI->connect($dsn,$user,$password);   
}

I have provided every information from an external file. I get the error message

DBI connect('dbname:**.**.**.**:3306','',...) failed: Access denied for user 'root'@'dbserver' (using password: NO) at line 89

Can't call method "prepare" on an undefined value at at line 97

I am very sure the root can connect from any host and the password is also correct.

One problem is that $self{...} has nothing to do with my $self = shift. You'd need to use $self->{...}. — cjm
– cjm, Commented May 3, 2012 at 18:30

derobert · Accepted Answer · 2012-05-03 18:42:43Z

3

First, your immediate problem, is as @Sinan Ünür says, that you need to change $self{platform} to $self->{platform}, etc.

Your second immediate problem is that it appears you're getting $user and $password from nowhere (they are not passed to the function, so they are undefined unless they are global variables), which would explain the using password: NO part of the error. Maybe those should be $self->{user} and $self->{password}?

You should considering put this at the top of your module, at least during development, to automatically catch errors like these:

use warnings qw(all);
use strict;

But I'd also comment, that from a design perspective, you really ought to treat DSNs as opaque strings. Each database has its own DSN format. So if you ever want to target a different database, you'll need a different DSN format. Or, possibly, someday MySQL will use a different format (it already has two). Either way, it'll be much easier to change it one place, in a configuration file, than to track down each place you concatenate the various pieces together.

edited May 3, 2012 at 18:42

answered May 3, 2012 at 18:30

derobert

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3 Comments

user1304082 Over a year ago

Like I have said in the problem statement, user and password are taken from an external file.

flesk Over a year ago

@user1304082: That's what you think anyway. It's quite evident that $user and $password aren't even declared in the scope you're using them, and that you need to provide more context if you want help solving your problem.

derobert Over a year ago

@user1304082 I have clarified my answer. You haven't passed $user and $password to the function (or, if you have, you're missing the my $user = shift;, my $password = shift; lines), so unless those are global variables, they're undefined. use strict will catch this.

gpojd · Accepted Answer · 2012-05-03 18:20:07Z

3

The key part of the warning that I see is "using password: NO". Check that the password is being set properly.

answered May 3, 2012 at 18:20

gpojd

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6 Comments

user1304082 Over a year ago

How do I do that ? and one more thing, I dont even have a host named 'dbserver'

gpojd Over a year ago

If you turn on use strict; and use warnings; for this, I'd bet that it would give you more information on how to fix this than SO users.

user1304082 Over a year ago

It gave me this warnings Global symbol "$user" requires explicit package name at dbAdmin.pm line 27. Global symbol "$password" requires explicit package name at dbAdmin.pm line 27

gpojd Over a year ago

Somewhere in your script, you need to have my $username = 'my_db_user'; and my $password = 'my_db_password';.

user1304082 Over a year ago

I did that, the machine is a new clean installation, do you think i need to install any mysql drivers on it before i use this script ?

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Sinan Ünür · Accepted Answer · 2012-05-03 18:22:23Z

2

Presumably, $self is a hashref, not a plain hash, and you don't have warnings on. So, turn them on, and use $self->{platform} etc.

answered May 3, 2012 at 18:22

Sinan Ünür

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3 Comments

user1304082 Over a year ago

these are the warnings I get

Global symbol "$user" requires explicit package name at dbAdmin.pm line 27. Global symbol "$password" requires explicit package name at dbAdmin.pm line 27

pilcrow Over a year ago

Quite right, but the OP's immediate problem is that the call to DBI->connect is failing.

Barry Over a year ago

Then clearly your variables $user and $password aren't getting set from the external file you mentioned. How are you doing that?

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