NAME¶
Rose::DB::Object::Loader - Automatically create Rose::DB::Object subclasses
based on database table definitions.
SYNOPSIS¶
Sample database schema:
CREATE TABLE vendors
(
id SERIAL NOT NULL PRIMARY KEY,
name VARCHAR(255) NOT NULL,
UNIQUE(name)
);
CREATE TABLE products
(
id SERIAL NOT NULL PRIMARY KEY,
name VARCHAR(255) NOT NULL,
price DECIMAL(10,2) NOT NULL DEFAULT 0.00,
vendor_id INT REFERENCES vendors (id),
status VARCHAR(128) NOT NULL DEFAULT 'inactive'
CHECK(status IN ('inactive', 'active', 'defunct')),
date_created TIMESTAMP NOT NULL DEFAULT NOW(),
release_date TIMESTAMP,
UNIQUE(name)
);
CREATE TABLE prices
(
id SERIAL NOT NULL PRIMARY KEY,
product_id INT NOT NULL REFERENCES products (id),
region CHAR(2) NOT NULL DEFAULT 'US',
price DECIMAL(10,2) NOT NULL DEFAULT 0.00,
UNIQUE(product_id, region)
);
CREATE TABLE colors
(
id SERIAL NOT NULL PRIMARY KEY,
name VARCHAR(255) NOT NULL,
UNIQUE(name)
);
CREATE TABLE product_color_map
(
product_id INT NOT NULL REFERENCES products (id),
color_id INT NOT NULL REFERENCES colors (id),
PRIMARY KEY(product_id, color_id)
);
To start, make a Rose::DB::Object::Loader object, specifying the database
connection information and an optional class name prefix.
$loader =
Rose::DB::Object::Loader->new(
db_dsn => 'dbi:Pg:dbname=mydb;host=localhost',
db_username => 'someuser',
db_password => 'mysecret',
db_options => { AutoCommit => 1, ChopBlanks => 1 },
class_prefix => 'My::Corp');
It's even easier to specify the database information if you've set up Rose::DB
(say, by following the instructions in Rose::DB::Tutorial). Just pass a
Rose::DB-derived object pointing to the database you're interested in.
$loader =
Rose::DB::Object::Loader->new(
db => My::Corp::DB->new('main'),
class_prefix => 'My::Corp');
Finally, automatically create Rose::DB::Object subclasses for all the tables in
the database. All it takes is one method call.
$loader->make_classes;
Here's what you get for your effort.
My::Corp::Product->new(name => 'Sled');
$p->vendor(name => 'Acme');
$p->prices({ price => 1.23, region => 'US' },
{ price => 4.56, region => 'UK' });
$p->colors({ name => 'red' },
{ name => 'green' });
$p->save;
$products =
My::Corp::Product::Manager->get_products_iterator(
query => [ name => { like => '%le%' } ],
with_objects => [ 'prices' ],
require_objects => [ 'vendor' ],
sort_by => 'vendor.name');
$p = $products->next;
print $p->vendor->name; # Acme
# US: 1.23, UK: 4.56
print join(', ', map { $_->region . ': ' . $_->price } $p->prices);
See the Rose::DB::Object and Rose::DB::Object::Manager documentation for learn
more about the features these classes provide.
The contents of the database now look like this.
mydb=# select * from products;
id | name | price | vendor_id | status | date_created
----+--------+-------+-----------+----------+-------------------------
1 | Sled 3 | 0.00 | 1 | inactive | 2005-11-19 22:09:20.7988
mydb=# select * from vendors;
id | name
----+--------
1 | Acme 3
mydb=# select * from prices;
id | product_id | region | price
----+------------+--------+-------
1 | 1 | US | 1.23
2 | 1 | UK | 4.56
mydb=# select * from colors;
id | name
----+-------
1 | red
2 | green
mydb=# select * from product_color_map;
product_id | color_id
------------+----------
1 | 1
1 | 2
DESCRIPTION¶
Rose::DB::Object::Loader will automatically create Rose::DB::Object subclasses
for all the tables in a database. It will configure column data types, default
values, primary keys, unique keys, and foreign keys. It can also discover and
set up inter-table relationships. It uses Rose::DB::Object's
auto-initialization capabilities to do all of this.
To do its work, the loader needs to know how to connect to the database. This
information can be provided in several ways. The recommended practice is to
set up Rose::DB according to the instructions in the Rose::DB::Tutorial, and
then pass a Rose::DB-derived object or class name to the loader. The loader
will also accept traditional DBI-style connection information: DSN, username,
password, etc.
Once the loader object is configured, the make_classes method does all the work.
It takes a few options specifying which tables to make classes for, whether or
not to make manager classes for each table, and a few other options. The
convention manager is used to convert table names to class names, generate
foreign key and relationship method names, and so on. The result of this
process is a suite of Rose::DB::Object (and Rose::DB::Object::Manager)
subclasses ready for use.
Rose::DB::Object::Loader inherits from, and follows the conventions of,
Rose::Object. See the Rose::Object documentation for more information.
GOTCHAS¶
Database schema information is extracted using DBI's schema interrogation
methods, which dutifully report exactly how the database describes itself. In
some cases, what the database reports about a particular table may not exactly
match what you specified in your table definition.
The most egregious offender is (surprise!) MySQL, which, to give just one
example, tends to offer up empty string default values for non-null character
columns. That is, if you write a table definition like this:
CREATE TABLE widgets
(
id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(64) NOT NULL
);
and then interrogate it using DBI, you will find that the "name"
column has a default value (as reflected in the "COLUMN_DEF" column
returned by DBI's
column_info() method) of '' (i.e., an empty string).
In other words, it's as if your table definition was this instead:
CREATE TABLE widgets
(
id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(64) NOT NULL DEFAULT ''
);
MySQL is full of such surprises, and it's not the only database to do such
things. Consult the documentation for your database (or do a Google search for
"<mydbname> gotchas") for the gory details.
To work around these kinds of problems, try the pre_init_hook feature. For
example, in your pre_init_hook subroutine you could walk over the list of
columns for each class, eliminating all the empty string default values (i.e.,
changing them to undef instead).
CONSTRUCTOR¶
- new PARAMS
- Returns a new Rose::DB::Object::Loader constructed
according to PARAMS, where PARAMS are name/value pairs. Any object method
is a valid parameter name.
OBJECT METHODS¶
- base_class CLASS
- This is an alias for the base_classes method.
- base_classes [ CLASS | ARRAYREF ]
- Get or set the list of base classes to use for the
Rose::DB::Object subclasses created by the make_classes method. The
argument may be a class name or a reference to an array of class names. At
least one of the classes should inherit from Rose::DB::Object.
Returns a list (in list context) or reference to an array (in scalar
context) of base class names. Defaults to a dynamically-generated
Rose::DB::Object subclass name.
- class_prefix [PREFIX]
- Get or set the prefix affixed to all class names created by
the make_classes method. If PREFIX doesn't end in "::", it will
be added automatically.
- convention_manager [ CLASS | MANAGER ]
- Get or set the Rose::DB::Object::ConventionManager-derived
class name or object to be used during the auto-initialization process for
each class created by the make_classes method. Returns a
Rose::DB::Object::ConventionManager-derived object, which defaults to a
new Rose::DB::Object::ConventionManager object.
Unless this attribute is explicitly set or fetched before the call to the
make_classes method, the convention manager object used by make_classes
will be produced by calling the convention_manager method of the metadata
object of the first (left-most) base class.
- db [DB]
- Get or set the Rose::DB-derived object used to connect to
the database. This object will be used by the make_classes method when
extracting information from the database. It will also be used as the
prototype for the db object used by each Rose::DB::Object subclass to
connect to the database.
Setting this attribute also sets the db_class attributes, overwriting any
previously existing value, and sets the db_dsn value to undef.
- db_catalog [CATALOG]
- Get or set the catalog for the database connection.
- db_class [CLASS]
- Get or set the name of the Rose::DB-derived class used by
the make_classes method to construct a db object if one has not been set
via the method of the same name.
Setting this attribute sets the db attribute to undef unless its class is
the same as CLASS.
- db_dsn [DSN]
- Get or set the DBI-style Data Source Name (DSN) used to
connect to the database. This will be used by the make_classes method when
extracting information from the database. The Rose::DB-derived objects
used by each Rose::DB::Object subclass to connect to the database will be
initialized with this DSN.
Setting this attribute immediately sets the dsn of the db attribute, if it
is defined.
- db_options [HASHREF]
- Get or set the options used to connect to the
database.
- db_password [PASSWORD]
- Get or set the password used to connect to the
database.
- db_schema [SCHEMA]
- Get or set the schema for the database connection.
- db_username [USERNAME]
- Get or set the username used to connect to the
database.
- exclude_tables [ REGEX | ARRAYREF ]
- Get or set a regular expression or reference to an array of
table names to exclude. Table names that match REGEX or are contained in
ARRAYREF will be skipped by default during calls to the make_classes
method. Tables without primary keys are automatically (and always)
skipped.
Table names are compared to REGEX and the names in ARRAYREF in a
case-insensitive manner. To override this in the case of the REGEX, add
"(?-i)" to the front of the REGEX. Otherwise, use the
filter_tables method instead.
- filter_tables CODEREF
- Get or set a reference to a subroutine that takes a single
table name argument and returns true if the table should be processed by
default during calls to the make_classes method, false if the table should
be skipped. The $_ variable will also be set to the table name before the
call to CODEREF.
This attribute should not be combined with the exclude_tables or
include_tables attributes.
- force_lowercase [BOOL]
- Get or set a boolean value that indicates whether or not
metadata entity names should be forced to lowercase even when the related
entity (e.g., table or column name) is uppercase or mixed case.
("Metadata entities" are thing like columns, relationships, and
foreign keys.) The default value undef.
- generate_manager_class_name CLASS [, CM]
- Given the name of a Rose::DB::Object-derived class, returns
a class name for a Rose::DB::Object::Manager-derived class to manage such
objects. The default implementation calls the auto_manager_class_name
method on the convention manager object passed as the optional CM
argument, or returned from the convention_manager method if a CM argument
is not passed.
- include_tables [ REGEX | ARRAYREF ]
- Get or set a regular expression or reference to an array of
table names to include. Table names that do not match REGEX or are not
contained in ARRAYREF will be skipped by default during calls to the
make_classes method. Tables without primary keys are automatically (and
always) skipped.
Table names are compared to REGEX and the names in ARRAYREF in a
case-insensitive manner. To override this in the case of the REGEX, add
"(?-i)" to the front of the REGEX. Otherwise, use the
filter_tables method instead.
- include_predicated_unique_indexes BOOL
- Get or set a boolean value that will be assigned to the
include_predicated_unique_indexes attribute of the
Rose::DB::Object::Metadata object for each class created by the
make_classes method. The default value is false.
- include_views BOOL
- If true, database views will also be processed by default
during calls to the make_classes method. Defaults to false.
- make_classes [PARAMS]
- Automatically create Rose::DB::Object and (optionally)
Rose::DB::Object::Manager subclasses for some or all of the tables in a
database. The class creation process is controlled by the loader object's
attributes. Optional name/value pairs passed to this method may override
some of those values. Valid PARAMS are:
- db [DB]
- The Rose::DB-derived object used to connect to the
database. This object will also be used as the prototype for the db object
used by each Rose::DB::Object subclass created by this call to
make_classes. Defaults to the value of the loader object's db
attribute.
- db_class [CLASS]
- The name of the Rose::DB-derived class used to construct a
db object if one has not been set via the parameter or object attribute of
the same name. Defaults to the value of the loader object's db_class
attribute.
- include_tables [ REGEX | ARRAYREF ]
- Table names that do not match REGEX or are not contained in
ARRAYREF will be skipped. Defaults to the value of the loader object's
include_tables attribute. Tables without primary keys are automatically
(and always) skipped.
Table names are compared to REGEX and the names in ARRAYREF in a
case-insensitive manner. To override this in the case of the REGEX, add
"(?-i)" to the front of the REGEX. Otherwise, use the
"filter_tables" parameter instead.
- exclude_tables [ REGEX | ARRAYREF ]
- Table names that match REGEX or are contained in ARRAYREF
will be skipped. Defaults to the value of the loader object's
exclude_tables attribute. Tables without primary keys are automatically
(and always) skipped.
Table names are compared to REGEX and the names in ARRAYREF in a
case-insensitive manner. To override this in the case of the REGEX, add
"(?-i)" to the front of the REGEX. Otherwise, use the
"filter_tables" parameter instead.
- filter_tables CODEREF
- A reference to a subroutine that takes a single table name
argument and returns true if the table should be processed, false if it
should be skipped. The $_ variable will also be set to the table name
before the call. This parameter cannot be combined with the
"exclude_tables" or "include_tables" options.
Defaults to the value of the loader object's filter_tables attribute,
provided that both the "exclude_tables" and
"include_tables" values are undefined. Tables without primary
keys are automatically skipped.
- force_lowercase BOOL
- A boolean value that indicates whether or not metadata
entity names should be forced to lowercase even when the related entity is
uppercase or mixed case. ("Metadata entities" are thing like
columns, relationships, and foreign keys.)
If this parameter is omitted and if the loader object's force_lowercase
attribute is not defined, then the value is chosen based on the database
currently being examined. If the database is Oracle, then it defaults to
true. Otherwise, it defaults to false.
The final value is propagated to the convention manager attribute of the
same name.
- include_predicated_unique_indexes BOOL
- This value will be assigned to the
include_predicated_unique_indexes attribute of the
Rose::DB::Object::Metadata object for each class created by this method.
Defaults to the value of the loader object's
include_predicated_unique_indexes attribute.
- include_views BOOL
- If true, database views will also be processed. Defaults to
the value of the loader object's include_views attribute.
- post_init_hook [ CODEREF | ARRAYREF ]
- A reference to a subroutine or a reference to an array of
code references that will be called just after each
Rose::DB::Object-derived class is initialized. Each referenced subroutine
will be passed the class's metadata object plus any arguments to the
initialize method. Defaults to the value of the loader object's
post_init_hook attribute.
- pre_init_hook [ CODEREF | ARRAYREF ]
- A reference to a subroutine or a reference to an array of
code references that will be called just before each
Rose::DB::Object-derived class is initialized. Each referenced subroutine
will be passed the class's metadata object plus any arguments to the
initialize method. Defaults to the value of the loader object's
pre_init_hook attribute.
- require_primary_key BOOL
- If true, then any table that does not have a primary key
will be skipped. Defaults to the value of the loader object's
require_primary_key attribute. Note that a Rose::DB::Object-derived class
based on a table with no primary key will not function correctly in all
circumstances. Use this feature at your own risk.
- warn_on_missing_pk BOOL
- This is an alias for the
"warn_on_missing_primary_key" parameter.
- warn_on_missing_primary_key BOOL
- If true, then any table that does not have a primary key
will trigger a warning.
If "require_primary_key" is false and the loader object's
warn_on_missing_primary_key attribute is undefined, or if the
"warn_on_missing_primary_key" parameter is set to an undefined
valur or is not passed to the make_classes call at all, then
"warn_on_missing_primary_key" is set to false. Otherwise, it
defaults to the value of the loader object's warn_on_missing_primary_key
attribute. Note that a Rose::DB::Object-derived class based on a table
with no primary key will not function correctly in all circumstances.
These complicated defaults are intended to honor the intentions of the
"require_primary_key" attribute/parameter. If not requiring
primary keys and no explicit decision has been made about whether to warn
about missing primary keys, either in the parameters to the make_classes
call or in the loader object itself, then we don't warn about missing
primary keys. The idea is that not requiring primary keys is a strong
indication that their absence is not worth a warning.
- with_foreign_keys BOOL
- If true, set up foreign key metadata for each
Rose::DB::Object-derived. Defaults to the value of the loader object's
with_foreign_keys attribute.
- with_managers BOOL
- If true, create Rose::DB::Object::Manager-derived manager
classes for each Rose::DB::Object subclass. Defaults to the value of the
loader object's with_managers attribute.
The manager class name is determined by passing the Rose::DB::Object-derived
class name to the generate_manager_class_name method.
The Rose::DB::Object subclass's metadata object's make_manager_class method
will be used to create the manager class. It will be passed the return
value of the convention manager's auto_manager_base_name method as an
argument.
- with_relationships [ BOOL | ARRAYREF ]
- A boolean value or a reference to an array of relationship
type names. If set to a simple boolean value, then all types of
relationships will be considered when making classes. If set to a list of
relationship type names, then only relationships of those types will be
considered. Defaults to the value of the loader object's
with_relationships attribute.
- with_unique_keys BOOL
- If true, set up unique key metadata for each
Rose::DB::Object-derived. Defaults to the value of the loader object's
with_unique_keys attribute.
Any remaining name/value parameters will be passed on to the call to
auto_initialize used to set up each class. For example, to ask the loader not
to create any relationships, pass the "with_relationships" parameter
with a false value.
$loader->make_classes(with_relationships => 0);
This parameter will be passed on to the auto_initialize method, which, in turn,
will pass the parameter on to its own call to the auto_init_relationships
method. See the Rose::DB::Object::Metadata documentation for more information
on these methods.
Each Rose::DB::Object subclass will be created according to the "best
practices" described in the Rose::DB::Object::Tutorial. If a base class
is not provided, one (with a dynamically generated name) will be created
automatically. The same goes for the db object. If one is not set, then a new
(again, dynamically named) subclass of Rose::DB, with its own private data
source registry, will be created automatically.
This method returns a list (in list context) or a reference to an array (in
scalar context) of the names of all the classes that were created. (This list
will include manager class names as well, if any were created.)
- make_modules [PARAMS]
- Automatically create Rose::DB::Object and (optionally)
Rose::DB::Object::Manager subclasses for some or all of the tables in a
database, then create Perl module (*.pm) files for each class.
This method calls make_classes to make the actual classes.
Note: If you are trying to regenerate a set of module files that
already exist in the target "module_dir", please make sure that
this "module_dir" is not in your @INC path. (That is,
make sure it is not in the set of paths that perl will search when looking
for module files in response to a "use" or "require"
statement.) More generally, you must make sure that existing versions of
the modules you are attempting to generate are not in your @INC path.
(If you do not do this, when make_classes makes a class and looks for a
related class, it will find and load the previously generated
".pm" file, which will then cause make_classes to skip that
class later when it sees that it already exists in memory. And if
make_classes skips it, make_modules will never see it and therefore will
never regenerate the ".pm" file.)
This method takes all of the same parameters as make_classes, with several
additions:
- module_dir DIR
- The path to the directory where the Perl module files will
be created. For example, given a DIR of "/home/john/lib", the
Perl module file for the class "My::DB::Object" would be located
at "/home/john/lib/My/DB/Object.pm".
Defaults to the value of the loader object's module_dir attribute. If the
module_dir attribute is also undefined, then the current working directory
(as determined by a call to cwd()) is used instead.
- module_preamble [ SCALAR | CODE ]
- If defined as a scalar, inserts the contents of the
variable into the auto-generated file before any of the auto-generated
class information. If provided as a code ref, calls the indicated
function, passing the metadata object as a parameter. (The metadata object
that belongs to the "object_class" and the
Rose::DB::Object::Manager-derived class name are passed if the module is a
Rose::DB::Object::Manager-derived class.) The returned value of the
function is inserted as the preamble text.
Defaults to to the value of the loader object's module_preamble
attribute.
- module_postamble [ SCALAR | CODE ]
- If defined as a scalar, inserts the contents of the
variable into the auto-generated file after any of the auto-generated
class information. If provided as a code ref, calls the indicated
function, passing the metadata object as a parameter. (The metadata object
that belongs to the "object_class" and the
Rose::DB::Object::Manager-derived class name are passed if the module is a
Rose::DB::Object::Manager-derived class.) The returned value of the
function is inserted as the postamble text.
Defaults to to the value of the loader object's module_postamble
attribute.
- module_dir [DIR]
- Get or set the path to the directory where make_modules
will create its Perl modules files. For example, given a DIR of
"/home/john/lib", make_modules would create the file
"/home/john/lib/My/DB/Object.pm" for the class
"My::DB::Object".
- module_preamble [ SCALAR | CODE ]
- If defined as a scalar, inserts the contents of the
variable into the auto-generated file before any of the auto-generated
class information. If provided as a code ref, calls the indicated
function, passing the metadata object as a parameter. (The metadata object
that belongs to the "object_class" and the
Rose::DB::Object::Manager-derived class name are passed if the module is a
Rose::DB::Object::Manager-derived class.) The returned value of the
function is inserted as the preamble text.
- module_postamble [ SCALAR | CODE ]
- If defined as a scalar, inserts the contents of the
variable into the auto-generated file after any of the auto-generated
class information. If provided as a code ref, calls the indicated
function, passing the metadata object as a parameter. (The metadata object
that belongs to the "object_class" and the
Rose::DB::Object::Manager-derived class name are passed if the module is a
Rose::DB::Object::Manager-derived class.) The returned value of the
function is inserted as the postamble text.
- pre_init_hook [CODE]
- Get or set a reference to a subroutine to be called just
before each Rose::DB::Object-derived class is initializeed within the
make_classes method. The subroutine will be passed the class's metdata
object as an argument.
- require_primary_key BOOL
- Get or set a boolean value that determines whether or not
the make_classes method will skip any table that does not have a primary
key will be skipped. Defaults to true.
Note that a Rose::DB::Object-derived class based on a table with no primary
key will not function correctly in all circumstances. Use this feature at
your own risk.
- warn_on_missing_pk BOOL
- This is an alias for the warn_on_missing_primary_key
method.
- warn_on_missing_primary_key BOOL
- Get or set a boolean value that determines whether or not
the make_classes method will emit a warning when it encounters a table
that does not have a primary key. Defaults to undefined.
- with_foreign_keys BOOL
- If true, the make_classes method will set up foreign key
metadata for each Rose::DB::Object-derived class it creates. Defaults to
true.
- with_managers [BOOL]
- If true, the make_classes method will create
Rose::DB::Object::Manager-derived manager classes for each
Rose::DB::Object subclass by default. Defaults to true.
The manager class name is determined by passing the Rose::DB::Object-derived
class name to the generate_manager_class_name method.
The Rose::DB::Object subclass's metadata object's make_manager_class method
will be used to create the manager class. It will be passed the return
value of the convention manager's auto_manager_base_name method as an
argument.
- with_relationships [ BOOL | ARRAYREF ]
- A boolean value or a reference to an array of relationship
type names. If set to a simple boolean value, then the make_classes method
will consider all types of relationships when making classes. If set to a
list of relationship type names, then only relationships of those types
will be considered by make_classes. Defaults to true.
- with_unique_keys BOOL
- If true, the make_classes method will set up unique key
metadata for each Rose::DB::Object-derived class it creates. Defaults to
true.
- manager_base_class CLASS
- This is an alias for the manager_base_classes method.
- manager_base_classes [ CLASS | ARRAYREF ]
- Get or set the list of base classes to use for the
Rose::DB::Object::Manager subclasses created by the make_classes method.
The argument may be a class name or a reference to an array of class
names. At least one of the classes should inherit from
Rose::DB::Object::Manager.
Returns a list (in list context) or reference to an array (in scalar
context) of base class names. Defaults to Rose::DB::Object::Manager.
AUTHOR¶
John C. Siracusa (siracusa@gmail.com)
LICENSE¶
Copyright (c) 2010 by John C. Siracusa. All rights reserved. This program is
free software; you can redistribute it and/or modify it under the same terms
as Perl itself.