Editing Create Export Plugins (section)

==Hello World export plugin==

http://en.wikipedia.org/wiki/Hello_world_program

Export plugins are stored in:

 /opt/eprints3/perl_lib/EPrints/Plugin/Export/

Create a new file in this directory called ''HelloWorld.pm'', and paste the following code into it (this is a useful template for writing export plugins!):

<pre>
package EPrints::Plugin::Export::HelloWorld;

use EPrints::Plugin::Export;
@ISA = ( "EPrints::Plugin::Export" );

use strict;

sub new
{
        my( $class, %opts ) = @_;
}

sub output_dataobj
{
        my( $plugin, $dataobj ) = @_;
}

1;
</pre>


The ''new'' subroutine creates the plugin - this is where you '''register''' the plugin with EPrints. The ''output_dataobj'' subroutine is where you '''convert''' EPrints data to the output format.

'''Perl notes:

# <tt>package ...</tt> - the plugin (Perl module) namespace, which should always be EPrints::Plugin::Export::''PluginID'' (note that the file should be called ''PluginID''.pm)
# <tt>use EPrints::Plugin::Export, @ISA=...</tt> - inherit all the internal wiring needed for EPrints to use your plugin

===Register Hello World plugin===

Add the following to the ''new'' subroutine to register the plugin with EPrints:

<pre>
sub new
{
        my( $class, %opts ) = @_;

        my $self = $class->SUPER::new( %opts );

        $self->{name} = "Hello, World!";
        $self->{accept} = [ 'dataobj/eprint', 'list/eprint' ];
        $self->{visible} = "all";
        $self->{suffix} = ".txt";
        $self->{mimetype} = "text/plain; charset=utf-8";

        return $self;
}
</pre>

===Convert EPrints data to Hello World data===

Add the following to the ''output_dataobj'' subroutine:

<pre>
sub output_dataobj
{
        my( $plugin, $dataobj ) = @_;

        my $title = $dataobj->get_value( "title" );

        return "Hello, World! $title\n\n";
} 
</pre>

This subroutine "converts" an eprint object by getting its title and using it in a Hello, World! message.

===Testing the Hello World plugin===

Save the ''HelloWorld.pm'' file and then restart the Web server, eg.:

 service httpd restart

'''Why do I need to restart the Web server?''' EPrints uses mod_perl which loads all Perl modules at start up; therefore whenever these modules change they need to be reloaded.

The Hello World export plugin handles lists of eprints and single eprints. Therefore, EPrints displays it in the list of export plugins on the search results page: 

[[Image:Hello-world-export.png|frame|none|Selecting the Hello World export plugin from the search results page]]

When the Hello World export plugin is activated, the ''convert_dataobj'' subroutine is applied to every item in the list to produce the result:

[[Image:Hello-world-export-result.png|frame|none|The output of the Hello World export plugin]]