Introduction

Data-centric applications can have many different architectures. In some of these architectures, the data is not even in the database itself. In these cases, a possible scenario can be that the data is collected by calling web services.

Essentially, a web service provider offers a way for external applications to unlock its data, but not give away total access to its database (or other data sources).

A call to a web service will have to satisfy certain standards as set by the World Wide Web consortium (W3C). Since the fourth version of Application Express, it provides the possibility to natively call two of these standards: Simple Object Access Protocol (SOAP) and Representational State Transfer (REST). But by using a little more PL/SQL and XML DB, it's possible to use any type of web service in APEX.

In this chapter we are going to create some examples of how to use web services in APEX.