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    Dancer2::Plugin::Database - easy database connections for Dancer

        use Dancer2;
        use Dancer2::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 = ?',
            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} }),


    Database connection details are read from your Dancer2 application config
    - see below.

    Provides an easy way to obtain a connected DBI database handle by simply
    calling the database keyword within your Dancer2 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

    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.)

    Connection details will be taken from your Dancer2 application config
    file, and should be specified as, for example:

                driver: 'mysql'
                database: 'test'
                host: 'localhost'
                port: 3306
                username: 'myusername'
                password: 'mypassword'
                connection_check_threshold: 10
                    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
    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

    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:

                driver: SQLite
                database: 'foo.sqlite'

    For Oracle, you may want to pass `sid' (system ID) to identify a
    particular database, e.g.:

                driver: Oracle
                host: localhost
                sid: ABC12

    If you need to connect to multiple databases, this is easy - just list
    them in your config under `connections' as shown below:

                        driver: "SQLite"
                        database: "foo.sqlite"
                        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');

    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.)

    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.

    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.


      # 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.

    This plugin uses Dancer2'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:

        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.

        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).

        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).

        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!

    David Precious, `<davidp@preshweb.co.uk>'

    This module is developed on Github at:


    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.

    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)


    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=Dancer2-Plugin-Database. I
    will be notified, and then you'll automatically be notified of progress
    on your bug as I make changes.

    You can find documentation for this module with the perldoc command.

        perldoc Dancer2::Plugin::Database

    You can also look for information at:

    * RT: CPAN's request tracker

    * AnnoCPAN: Annotated CPAN documentation

    * CPAN Ratings

    * Search CPAN

    You can find the author on IRC in the channel `#dancer' on

    Copyright 2010-2016 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.