ProxyPrefix

Time and again, there are threads on library mailing lists asking for a tool that will allow easy creation of proxied URLs. There are many questions, but few answers, especially answers that are not tied into a specific content management solution.

EZproxy took a half step with the /encode_url functionality. This allows you to paste a URL and have it properly quoted to add to the proxy login URL. But this does not go far enough. What happens when the database vendor uses a session ID in its URL? Or what happens if you need to add credentials or entry point data to the URL? The /encode_url feature does nothing to address either of these issues.

With ProxyPrefix, there is now a front-end solution available that does not care if it is being run on a static page, served from a LMS, or any other server back-end technology (PHP, Java, Python, Perl, ASP, etc).

You start with a simple list of resources on a web page. How the links are inserted into the web page is immaterial:

Online Resources:
<ul>
<li><a href="http://books.google.com">Google Books</a></li>
<li><a href="http://www.ncbi.nlm.nih.gov/pubmed">PUBMED</a></li>
<li><a href="http://www.ipl.org">Internet Public Library</a></li>
</ul>

To convert these into proxied links, historically you would need to manually add a proxy prefix to each and every URL.

You would also have to worry about encoding any special characters (?, &, and #) that may be in the URL, to ensure that the proxy server does not consume those parameters as part of the login processing. You eventually wind up with a page that starts looking more like this:

Online Resources:
<ul><li><a href="http://proxy.example.edu/login?qurl=http%3A%2F%2Fbooks.google.com">Google Books</a></li>
<li><a href="http://proxy.example.edu/login?qurl=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpubmed">PUBMED</a></li>
<li><a href="http://proxy.example.edu/login?qurl=http%3A%2F%2Fwww.ipl.org">Internet Public Library</a></li
>
</ul>

Go ahead, take a minute to de-glaze your eyes after looking at that.

Instead of all that headache, ProxyPrefix allows you to simply add one line of JavaScript to your page instead:

Online Resources:
<ul>
<li><a href="http://books.google.com">Google Books</a></li>
<li><a href="http://www.ncbi.nlm.nih.gov/pubmed">PUBMED</a></li>
<li><a href="http://www.ipl.org">Internet Public Library</a></li>
</ul>

$('a').ProxyPrefix();

No server-side changes required, all of the changes to the anchor href attribute happen on the fly in the browser instead.

Using ProxyPrefix

ProxyPrefix is built as a jQuery Plugin, and uses the URIjs library for URI parsing.

Demo

A demonstration page is available. In the demo, a simple form allows the proxy server name to be specified, accepts a URL to an online resource. After encoding the URL, you can then test that the URL functions correctly, using the Test button to open the resource via the proxy server.

Examples

$('a').ProxyPrefix();

This will apply the default options to all HTML anchor elements on the page.

hostnames

$('a').ProxyPrefix( { hostnames: new Array( 
	'proxy.example.edu', 
	'proxy1.example.edu', 
	'proxy2.example.edu'} 
);

This will set the list of proxy servers used. NOTE: the first proxy server listed is the default proxy server, and will be used to generate the hostname portion of the proxy prefix.

loginpath

$('a').ProxyPrefix( { loginpath: '/sso/login' } );

This will set the path portion of the proxy prefix to /sso/login.

attribute

$('form').ProxyPrefix( { attribute: 'action' } );

The default options are designed to work against HTML anchors (<a> elments in the web age), but can be adapated to work against HTML forms as well. Any web page element that can be changed using the jQuery .attr() function can be used with ProxyPrefix.

protocols

$('a').ProxyPrefix( { protocols: new Array( 'http', 'https', 'gopher' ) } );

This will set the protocols that your proxy server can service. If a protocol is encountered that is not in this array, the $.error() method is called and the URL is skipped.

remove

var remove_options = {
    'web.ebscohost.com': new Array( 'sid' )
}
$('a').ProxyPrefix( { remove: remove_options } );

The remove paramter spcifies an array where the keys are the hostname for the database, and the values are the names of query parameters that will be stripped from the URL. In this case, the sid parameter is being removed, since it represents a session identifier that is not valid for future sessions.

append

var append_options = {
 'search.ebscohost.com': {
   'auth': 'uid',
   'user': 'libraryresearch',
   'password': 'libraryresearch'
  }
}
$('a').ProxyPrefix( { append: append_options } );

The append paramter spcifies an array where the keys are the hostname for the database, and the values are the names of query parameters that will be added to the URL. In this case, the auth, user, and password parameters are being added, since they are required for successful authentication to the service.