NAME
Dancer::Plugin::Database - easy database connections for Dancer
applications
SYNOPSIS
use Dancer;
use Dancer::Plugin::Database;
# Calling the database keyword will get you a connected database handle:
get '/widget/view/:id' => sub {
my $sth = database->prepare(
'select * from widgets where id = ?',
);
$sth->execute(params->{id});
template 'display_widget', { widget => $sth->fetchrow_hashref };
};
# The handle is a Dancer::Plugin::Database::Core::Handle object, which subclasses
# DBI's DBI::db handle and adds a few convenience features, for example:
get '/insert/:name' => sub {
database->quick_insert('people', { name => params->{name} });
};
get '/users/:id' => sub {
template 'display_user', {
person => database->quick_select('users', { id => params->{id} }),
};
};
dance;
Database connection details are read from your Dancer application config
- see below.
DESCRIPTION
Provides an easy way to obtain a connected DBI database handle by simply
calling the database keyword within your Dancer application
Returns a Dancer::Plugin::Database::Core::Handle object, which is a subclass
of DBI's `DBI::db' connection handle object, so it does everything you'd
expect to do with DBI, but also adds a few convenience methods. See the
documentation for Dancer::Plugin::Database::Core::Handle for full details of
those.
Takes care of ensuring that the database handle is still connected and
valid. If the handle was last asked for more than
`connection_check_threshold' seconds ago, it will check that the
connection is still alive, using either the `$dbh->ping' method if the
DBD driver supports it, or performing a simple no-op query against the
database if not. If the connection has gone away, a new connection will
be obtained and returned. This avoids any problems for a long-running
script where the connection to the database might go away.
Care is taken that handles are not shared across processes/threads, so
this should be thread-safe with no issues with transactions etc. (Thanks
to Matt S Trout for pointing out the previous lack of thread safety.
Inspiration was drawn from DBIx::Connector.)
CONFIGURATION
Connection details will be taken from your Dancer application config
file, and should be specified as, for example:
plugins:
Database:
driver: 'mysql'
database: 'test'
host: 'localhost'
port: 3306
username: 'myusername'
password: 'mypassword'
connection_check_threshold: 10
dbi_params:
RaiseError: 1
AutoCommit: 1
on_connect_do: ["SET NAMES 'utf8'", "SET CHARACTER SET 'utf8'" ]
log_queries: 1
handle_class: 'My::Super::Sexy::Database::Handle'
The `connection_check_threshold' setting is optional, if not provided,
it will default to 30 seconds. If the database keyword was last called
more than this number of seconds ago, a quick check will be performed to
ensure that we still have a connection to the database, and will
reconnect if not. This handles cases where the database handle hasn't
been used for a while and the underlying connection has gone away.
The `dbi_params' setting is also optional, and if specified, should be
settings which can be passed to `DBI->connect' as its fourth argument;
see the DBI documentation for these.
The optional `on_connect_do' setting is an array of queries which should
be performed when a connection is established; if given, each query will
be performed using `$dbh->do'. (If using MySQL, you might want to use
this to set `SQL_MODE' to a suitable value to disable MySQL's built-in
free data loss 'features', for example:
on_connect_do: "SET SQL_MODE='TRADITIONAL'"
(If you're not familiar with what I mean, I'm talking about the insane
default behaviour of "hmm, this bit of data won't fit the column you're
trying to put it in.. hmm, I know, I'll just munge it to fit, and throw
a warning afterwards - it's not like you're relying on me to, y'know,
store what you ask me to store". See
http://effectivemysql.com/presentation/mysql-idiosyncrasies-that-bite/
for just one illustration. In hindsight, I wish I'd made a sensible
`sql_mode' a default setting, but I don't want to change that now.)
The optional `log_queries' setting enables logging of queries generated
by the helper functions `quick_insert' et al in
Dancer::Plugin::Database::Core::Handle. If you enable it, generated queries
will be logged at 'debug' level. Be aware that they will contain the
data you're passing to/from the database, so be careful not to enable
this option in production, where you could inadvertently log sensitive
information.
If you prefer, you can also supply a pre-crafted DSN using the `dsn'
setting; in that case, it will be used as-is, and the
driver/database/host settings will be ignored. This may be useful if
you're using some DBI driver which requires a peculiar DSN.
The optional `handle_class' defines your own class into which database
handles should be blessed. This should be a subclass of
Dancer::Plugin::Database::Core::Handle (or DBI::db directly, if you just want
to skip the extra features).
You will require slightly different options depending on the database
engine you're talking to. For instance, for SQLite, you won't need to
supply `hostname', `port' etc, but will need to supply `database' as the
name of the SQLite database file:
plugins:
Database:
driver: SQLite
database: 'foo.sqlite'
For Oracle, you may want to pass `sid' (system ID) to identify a
particular database, e.g.:
plugins:
Database:
driver: Oracle
host: localhost
sid: ABC12
DEFINING MULTIPLE CONNECTIONS
If you need to connect to multiple databases, this is easy - just list
them in your config under `connections' as shown below:
plugins:
Database:
connections:
foo:
driver: "SQLite"
database: "foo.sqlite"
bar:
driver: "mysql"
host: "localhost"
....
Then, you can call the `database' keyword with the name of the database
connection you want, for example:
my $foo_dbh = database('foo');
my $bar_dbh = database('bar');
RUNTIME CONFIGURATION
You can pass a hashref to the `database()' keyword to provide
configuration details to override any in the config file at runtime if
desired, for instance:
my $dbh = database({ driver => 'SQLite', database => $filename });
(Thanks to Alan Haggai for this feature.)
AUTOMATIC UTF-8 SUPPORT
As of version 1.20, if your application is configured to use UTF-8
(you've defined the `charset' setting in your app config as `UTF-8')
then support for UTF-8 for the database connection will be enabled, if
we know how to do so for the database driver in use.
If you do not want this behaviour, set `auto_utf8' to a false value when
providing the connection details.
GETTING A DATABASE HANDLE
Calling `database' will return a connected database handle; the first
time it is called, the plugin will establish a connection to the
database, and return a reference to the DBI object. On subsequent calls,
the same DBI connection object will be returned, unless it has been
found to be no longer usable (the connection has gone away), in which
case a fresh connection will be obtained.
If you have declared named connections as described above in 'DEFINING
MULTIPLE CONNECTIONS', then calling the database() keyword with the name
of the connection as specified in the config file will get you a
database handle connected with those details.
You can also pass a hashref of settings if you wish to provide settings
at runtime.
CONVENIENCE FEATURES (quick_select, quick_update, quick_insert, quick_delete)
The handle returned by the `database' keyword is a
Dancer::Plugin::Database::Core::Handle object, which subclasses the `DBI::db'
DBI connection handle. This means you can use it just like you'd
normally use a DBI handle, but extra convenience methods are provided,
as documented in the POD for Dancer::Plugin::Database::Core::Handle.
Examples:
# Quickly fetch the (first) row whose ID is 42 as a hashref:
my $row = database->quick_select($table_name, { id => 42 });
# Fetch all badgers as an array of hashrefs:
my @badgers = database->quick_select('animals', { genus => 'Mellivora' });
# Update the row where the 'id' column is '42', setting the 'foo' column to
# 'Bar':
database->quick_update($table_name, { id => 42 }, { foo => 'Bar' });
# Insert a new row, using a named connection (see above)
database('connectionname')->quick_insert($table_name, { foo => 'Bar' });
# Delete the row with id 42:
database->quick_delete($table_name, { id => 42 });
# Fetch all rows from a table (since version 1.30):
database->quick_select($table_name, {});
There's more extensive documentation on these features in
Dancer::Plugin::Database::Core::Handle, including using the `order_by',
`limit', `columns' options to sort / limit results and include only
specific columns.
HOOKS
This plugin uses Dancer's hooks support to allow you to register code
that should execute at given times - for example:
hook 'database_connected' => sub {
my $dbh = shift;
# do something with the new DB handle here
};
Currrently defined hook positions are:
`database_connected'
Called when a new database connection has been established, after
performing any `on_connect_do' statements, but before the handle is
returned. Receives the new database handle as a parameter, so that
you can do what you need with it.
`database_connection_lost'
Called when the plugin detects that the database connection has gone
away. Receives the no-longer usable handle as a parameter, in case
you need to extract some information from it (such as which server
it was connected to).
`database_connection_failed'
Called when an attempt to connect to the database fails. Receives a
hashref of connection settings as a parameter, containing the
settings the plugin was using to connect (as obtained from the
config file).
`database_error'
Called when a database error is raised by `DBI'. Receives two
parameters: the error message being returned by DBI, and the
database handle in question.
If you need other hook positions which would be useful to you, please
feel free to suggest them!
AUTHOR
David Precious, `<davidp@preshweb.co.uk>'
CONTRIBUTING
This module is developed on Github at:
http://github.com/bigpresh/Dancer-Plugin-Database
Feel free to fork the repo and submit pull requests! Also, it makes
sense to watch the repo on GitHub for updates.
Feedback and bug reports are always appreciated. Even a quick mail to
let me know the module is useful to you would be very nice - it's nice
to know if code is being actively used.
ACKNOWLEDGEMENTS
Igor Bujna
Franck Cuny
Alan Haggai
Christian Sánchez
Michael Stiller
Martin J Evans
Carlos Sosa
Matt S Trout
Matthew Vickers
Christian Walde
Alberto Simões
James Aitken (LoonyPandora)
Mark Allen (mrallen1)
Sergiy Borodych (bor)
Mario Domgoergen (mdom)
Andrey Inishev (inish777)
Nick S. Knutov (knutov)
Nicolas Franck (nicolasfranck)
mscolly
BUGS
Please report any bugs or feature requests to
`bug-dancer-plugin-database at rt.cpan.org', or through the web
interface at
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Dancer-Plugin-Database. I
will be notified, and then you'll automatically be notified of progress
on your bug as I make changes.
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc Dancer::Plugin::Database
You can also look for information at:
* RT: CPAN's request tracker
http://rt.cpan.org/NoAuth/Bugs.html?Dist=Dancer-Plugin-Database
* AnnoCPAN: Annotated CPAN documentation
http://annocpan.org/dist/Dancer-Plugin-Database
* CPAN Ratings
http://cpanratings.perl.org/d/Dancer-Plugin-Database
* Search CPAN
http://search.cpan.org/dist/Dancer-Plugin-Database/
You can find the author on IRC in the channel `#dancer' on
<irc.perl.org>.
LICENSE AND COPYRIGHT
Copyright 2010-12 David Precious.
This program is free software; you can redistribute it and/or modify it
under the terms of either: the GNU General Public License as published
by the Free Software Foundation; or the Artistic License.
See http://dev.perl.org/licenses/ for more information.
SEE ALSO
Dancer
DBI
Dancer::Plugin::SimpleCRUD