eBay Hacks, 2nd Edition

Hacks 102–125

eBay is more than just a web site. It’s a platform upon which you can build your own applications and with which you can extend your business.

The eBay Application Programming Interfacer (API) is a set of functions you can integrate with your applications to communicate directly with eBay. Use the API to retrieve details about an auction, perform searches, list a seller’s current items, and even create new auction listings. Think of the API as a back door of sorts, a way for developers to interact with the eBay engine and auction database without using the standard web interface.

The possibilities of such a system are limitless. Businesses can use the eBay API to link their inventory and sales databases with listings, cutting out most of the labor that would otherwise be involved in selling large numbers of items. Developers can use the API to construct auction management applications for themselves, their companies, or even for commercial sale. And, of course, individual buyers and sellers on eBay can use the API to do a little friendly hacking, as described throughout the rest of this chapter.

How the eBay API Works

The underlying process of placing a call to the API is conceptually quite simple. First, your program sends an XML string to eBay with the name of the API call and any additional required fields. Here’s an example XML request for the GetSearchResults function:

 <?xml version='1.0' encoding='iso-8859-1'?> <request> <RequestUserId>my_user_id</RequestUserId> ...