Description
"CGI::Uploader::Cookbook" is a tutorial that accompanies the CGI::Uploader distribution. It shows example syntax for common uses."CGI::Uploader" module is designed to help with the task of managing files uploaded through a CGI application. The files are stored on the file system, and the file attributes stored in a SQL database.
Introduction to CGI::Uploader
A Little History
The release of this module represents a culmination of seven years of experience managing file uploads as a professional website developer for Summersault, LLC (<http://www.summersault.com/>). Over that time I noticed patterns that were re-usable from project to project. I went through several versions and rewrites of modules that attempted to be 'generic' and not need modification when the next project came along. With CGI::Uploader, I believe I finally have a solution that I will continue to be happy with and I think others will be find generally useful. Enjoy!Freedom of Choice
I endeavored to make CGI::Uploader to work within a variety of system designs. It offers you freedom choice in the following areas:-
Database Choice
MySQL and Postgres are supported directly. The SQL used is very simple--- support for additional databases should be trivial.
-
Choice of Query Provider
The query object used may provided by "CGI.pm", "CGI::Simple" or "Apache::Request". Another source could be used by overriding the "upload" method.
-
File Storage Schemes for Large and Small Projects
For small projects, all uploads can be stored in a single directory. For large projects, we provide the "md5" file scheme, which should scale well to millions of images, without burdening any single directory with storing too many of them.
-
Choice of Data Display
Because the meta data is stored in a straightforward SQL database table, you can retrieve your data and display in any number of custom ways. Several functions are also built in to help with common display tasks. The "build_loc()" method is used to construct the file system or URL path of an image, given it's ID and extension.
"fk_meta()" provides an easy way to get the meta data of an upload by relating it to a foreign key in another table.
Finally, "transform_meta()" is a basic function which transforms a hashref of data from the database into a format more useful for display, producing a hash that looks like this:
{ my_custom_prefix_id => 523, my_custom_prefix_url => 'http://localhost/images/uploads/523.pdf', my_custom_prefix_width => 23, my_custom_prefix_height => 46, } -
Image Processor
While "CGI::Uploader" works with all types of file uploads, it contains a number of features to help with common tasks associated with image uploads.
"Image::Magick" is the preferred image processing module for to use when creating the thumbnails. Support for "GD" is in progress. "GD" supports many fewer formats, but also has much fewer dependencies to get installed than "Image::Magick" does. Another providers could be used by extending or overriding the "gen_thumb()" method.
Just Three Essential Methods to Learn
A goal of <CGI::Uploader> is to provide a high-level interface to make managing file uploads easy. Only three methods are needed to manage all the functions needed to store, update, delete and view the uploads attached to some database entity. Those methods are "store_uploads()", "delete_checked_uploads()" and "fk_meta".More methods when you need them
When your needs before more complex, you can call the lower-level functions in "CGI::Uploader" to meet your needs. Most functions use file names to access file uploads, so it's easy to use the module to manipulate files from other sources than the browser upload field.For example, the "gen_thumb()" method is general purpose thumbnail creating routine.
Browse, Read, Edit, Add, Delete (BREAD) Example Application
The following sections will provide a walk through of a simple application using CGI::Uploader. This is intended to provide the picture of how this module can be used. Some details have been glossed over. For a complete, working example application, please see the "examples" directory of the distribution.Before "CGI::Uploader" can be useful, some setup needs to be done. You need some database tables to store the information in.
Example Database
For these examples, we'll set up some tables to manage photos of friends. Here is the SQL to create such tables with Postgres:
-- Note the Postgres specific syntax here
CREATE SEQUENCE upload_id_seq;
CREATE TABLE uploads (
upload_id int primary key not null
default nextval('upload_id_seq'),
mime_type character varying(64),
extension character varying(8), -- file extension
width integer,
height integer,
gen_from_id integer
);
CREATE SEQUENCE friend_id_seq;
CREATE TABLE address_book (
friend_id int primary key NOT NULL DEFAULT nextval('friend_id_seq'),
full_name varchar(64),
-- these two reference uploads('upload_id'),
photo_id int,
photo_thumbnail_id int
);
(MySQL is also supported. Check in the distribution for sample SQL 'Create' scripts for both MySQL and Postgresql databases).
Object Creation
You can create one "CGI::Uploader" object and use it for adding, updating, viewing and deleting uploads. So don't despair that it has a few required parameters--- you only need to type them once! :)
use CGI::Uploader::Transform::ImageMagick;
my $u = CGI::Uploader->new(
spec => {
photo => {
gen_files => {
photo_thumbnail => gen_thumb({ w => 100, h => 100}),
}
}
}
updir_url => 'http://localhost/uploads',
updir_path => '/home/friends/www/uploads',
dbh => $dbh,
);
Adding a Database Record and Related Uploads
Before we can do anything else with the uploads, we need to get some added into the system."CGI::Uploader" is designed to make this happening easily as part of the normal process of adding a normal database record. In this case, we'll be adding a friend.
Example 'Add Form'
Here's the form used to add a friend. It includes fields for the friend's name, and a photo of them.
<form action="your-script.cgi" enctype="multipart/form-data" METHOD="POST">
Friend Name: <input type="text" name="full_name"> <br />
Image: <input type="file" name="photo">
<input type="submit">
</form>
Notice that the 'enctype' is important for file uploads to work.
Notice we have a text field for a 'full_name' and a file upload field named 'photo'.
Processing the Add Form
AS a first step for processing the 'add form', I recommend validating the form with Data::FormValidator. It includes several routines just to validate file uploads. However, it's not necessary to validate the form.
# CGI::Simple provides a CGI.pm-like interface with much better performance
use CGI::Simple;
my $q = CGI::Simple->new();
my $form = $q->Vars;
my $friend = $u->store_uploads($form);
# Now the $friend hash been transformed so it can easily inserted
# It now looks like this:
# {
# full_name => 'M. Lewis',
# photo_id => 3,
# photo_thumbnail_id => 4,
# }
# I like to use SQL::Interp for easy inserts.
# See DBIx::Simple for an even more friendly wrapper.
use SQL::Interp 'sql_interp';
$dbh->do(sql_interp "INSERT INTO address_book",$friend);
Database Result of Adding
Here's what ended up in the database:
address_book table:
friend_id | full_name | photo_id | photo_thumbnail_id
-----------------------------------------------------
2 | M. Lewis | 3 | 4
uploads table:
upload_id | mime_type | extension | width | height | gen_from_id
--------------------------------------------------------------------
3 | image/png | .png | 200 | 400 |
4 | image/png | .png | 50 | 100 | 3
The files are stored on the file system. '4.png' was generated on the server a thumbnail of 3.png.
/home/friends/www/uploads/3.png /home/friends/www/uploads/4.png
Displaying & Linking to Uploads
You don't strictly need this module to display the uploaded image. You could construct your own database queries and URLs instead. However, the "fk_meta" method is provided to simplify things for you.Continuing with the example above, we would use this code to generate the details we need to display and link to the photo and thumbnail:
my $href = $u->fk_meta(
table => 'address_book',
where => { friend_id => 2 },
prefixes => [qw/photo photo_thumbnail/],
);
That will fetch the details of the photo and thumbnail associated with the friend who is an ID of ``2''.
The resulting hashref will look something like this:
{
photo_id => 3,
photo_url =>'http://localhost/uploads/3.png?23',
photo_width => 200,
photo_height => 400',
photo_thumbnail_id => 4,
photo_thumbnail_url =>'http://localhost/uploads/4.png?23',
photo_thumbnail_width => 50,
photo_thumbnail_height => 200',
}
This hashref can often be passed directly to a templating system such as HTML::Template for display.
You may be wondering about the query strings on the URLS. These are random numbers to defeat browser image caching, which is very useful on ``edit'' forms. This behavior may change or become optional in a future release.
Displaying an Update Form
So now we've added 'M. Lewis' to our friend database and displayed his photo on the web. M. Lewis turned out not to be happy about this. He reports that the photo used was not his 'good side' and has sent a 'better' photo to use.So now we need to have a form to update the photo from.
The form to update the upload will be a lot like the 'add form'. Additionally, it's nice to display a link to current upload on the form. This can be done using "fk_meta", as demonstrated above.
Our Update Form might look like this if we are using HTML::Template for display:
<form action="your-script.cgi" enctype="multipart/form-data" METHOD="POST">
<P>Friend Name: <input type="text" name="full_name"> </p>
<P>
<a href="<tmpl_var photo_url>">Current Image</a> <br/>
<input type="checkbox" value="1" name="photo_delete"> Delete Image?
</P>
<input type="hidden" name="photo_id" value="<tmpl_var photo_id>">
<p>Image: <input type="file" name="photo"></p>
<input type="submit">
</form>
Processing an Update Form
Processing an update form is the most complicated part of application. From this form it's possible to add, update and delete uploadsTo process the update form, we'll first delete any uploads that the user has requested to remove. Next, add and update any other uploads as need.
my $friend = $q->Vars;
my @fk_names = $u->delete_checked_uploads;
map { $friend->{$_} = undef } @fk_names;
delete $friend->{photo_delete};
$friend = $u->store_uploads($friend);
Although the call to "store_uploads()" looks the same as it did for adding a record, it works a little different now. Notice we passed a photo_id through the form above. Because this is present, that record will be updated instead of creating a new one.
Recipe Idea: Put an existing directory of photos on line
You have an existing directory full of JIGS that you want to put on-line as a photo gallery, with medium and small versions created of all the images. "CGI::Uploader" is versatile enough to help in this situation as well.Your spec might look like this:
large_jpeg => [
{ name => 'medium', w => 500, },
{ name => 'small', w => 250,
],
From there, read in all the file names and store all the files, with the smaller versions being created automatically for you along the way.
for my $jpeg (<*.jpg>) {
my %entity_upload_extra = $self->store_upload(
file_field => 'large_jpeg',
src_file => $jpeg,
uploaded_mt => 'image/jpeg',
file_name => $jpeg,
);
}
Now you may want to display a page containing all of the smallest thumbnails. If these IDs had been stored in another table, we could use fk_meta() to get all of the small thumbnails.
In this case, it is still possible to get a reasonable result by selecting images based on their size.
[TODO: example code for this needs to be written. ]
Recipe Idea: Handling anonymous image uploads
It is also possible with CGI::Uploader to have many ``anynonmous'' uploads associated with another entity in the database.[ TODO: And the documentation for how to that still needs to be written. :) ]