libcgi-uploader-perl 2.18-1 / usr / share / perl5 / CGI / Uploader / Cookbook.pod

=head1 NAME

CGI::Uploader::Cookbook - Examples of CGI::Uploader usage


=head1 Description

C<CGI::Uploader::Cookbook> is a tutorial that accompanies the B<CGI::Uploader> 
distribution. It shows example syntax for common uses.

C<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. 

=head1 Introduction to CGI::Uploader

=head2 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 (L<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!

=head2 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:

=over

=item * Database Choice

MySQL and Postgres are supported directly. The SQL used is very simple-- support 
for additional databases should be trivial.

=item * Choice of Query Provider

The query object used may provided by C<CGI.pm>, C<CGI::Simple> or
C<Apache::Request>. Another source could be used by overriding the C<upload>
method.

=item * 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 C<md5> file scheme, which should scale well to
millions of images, without burdening any single directory with storing too
many of them.

=item * 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 C<build_loc()> method is
used to construct the file system or URL path of an image, given it's ID and extension.

C<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, C<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,
 }

=item * Image Processor

While C<CGI::Uploader> works with all types of file uploads, it contains a number
of features to help with common tasks associated with image uploads.

C<Image::Magick> is the preferred image processing module for to use when
creating the thumbnails. Support for C<GD> is in progress. C<GD> supports many
fewer formats, but also has much fewer dependencies to get installed than
C<Image::Magick> does. Another providers could be used by extending or
overriding the C<gen_thumb()> method.

=back

=head2 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 C<store_uploads()>, C<delete_checked_uploads()> and C<fk_meta>.

=head2 More methods when you need them 

When your needs before more complex, you can call the lower-level functions in C<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 C<gen_thumb()> method is general purpose thumbnail creating routine.

=head1 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 C<examples> directory of the distribution.

Before C<CGI::Uploader> can be useful, some setup needs to be done.
You need some database tables to store the information in.

=head2 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 
 );

(I<MySQL> is also supported. Check in the distribution for sample SQL 'Create'
scripts for both I<MySQL> and I<Postgresql> databases).

=head2 Object Creation

You can create one C<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,	

 );

=head1 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.

C<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.

=head2 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'.  

=head2 Processing the Add Form

AS a first step for processing the 'add form', I recommend validating
the form with L<Data::FormValidator|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);


=head2 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

=head1 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 C<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
L<HTML::Template|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.

=head1 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 C<fk_meta>, as demonstrated above.

Our Update Form might look like this if we are using L<HTML::Template|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>

=head2 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 uploads  

To 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 C<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.

=head1 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.
C<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. ] 

=head1 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. :) ]  

=head1 See Also

L<CGI::Uploader|CGI::Uploader>

=head1 Author

  Mark Stosberg  <mark@summersault.com>

=cut