Java, XPath, XML and Facebook

PeopleSoft's Integration Broker and Web Services provide an excellent framework for web services integration. But what if your PeopleSoft system needs synchronous access to another system that doesn't publish web services? For example, let's say you need to communicate with a system like Facebook that has a Java client library (yes, Facebook has a REST-based API, but using the existing Java client is much easier than creating all of the messages, handlers, and Facebook specific publishing logic). Even though we can call Java directly from PeopleCode, the Facebook methods return a value of type org.w3c.dom.Document. Since this return value is a Java object, not a PeopleCode XmlDoc, you cannot use the standard PeopleCode Node methods to extract values from the resultant document. In the absence of an additional client library, we would have to write DOM traversal code to select and concatenate the text node values contained in the Facebook response elements. Fortunately, the PeopleSoft application server installation includes the Xalan XML processor. The Xalan client library includes the org.apache.xpath.XPathAPI class that can be used to select values from a Java DOM Document similar to the XmlDoc.FindNode method. Here is an example of using the XPathAPI in PeopleCode to extract the name of the first friend from a Facebook friends query:

Local JavaObject &results = &fbClient.fql_query("SELECT uid, name, status FROM user WHERE uid IN (SELECT uid2 FROM friend WHERE uid1 = '" | &uid | "')");
Local JavaObject &xpath = GetJavaClass("org.apache.xpath.XPathAPI");
Local string &name = &xpath.selectNodeList(&results, "/fql_query_response/user[1]/name/text()");