The Web Application Description Language (WADL) is a machine-readable
XML
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing data. It defines a set of rules for encoding electronic document, documents in a format that is both human-readable and Machine-r ...
description of
HTTP
HTTP (Hypertext Transfer Protocol) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, wher ...
-based
web service
A web service (WS) is either:
* a service offered by an electronic device to another electronic device, communicating with each other via the Internet, or
* a server running on a computer device, listening for requests at a particular port over a n ...
s. WADL models the resources provided by a service and the relationships between them. WADL is intended to simplify the reuse of web services that are based on the existing HTTP architecture of the Web. It is platform and language independent and aims to promote reuse of applications beyond the basic use in a web browser.
WADL was submitted to the
World Wide Web Consortium
The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working together in ...
by
Sun Microsystems
Sun Microsystems, Inc., often known as Sun for short, was an American technology company that existed from 1982 to 2010 which developed and sold computers, computer components, software, and information technology services. Sun contributed sig ...
on 31 August 2009, but the consortium has no current plans to standardize it. WADL is the
REST
REST (Representational State Transfer) is a software architectural style that was created to describe the design and guide the development of the architecture for the World Wide Web. REST defines a set of constraints for how the architecture of ...
equivalent of
SOAP
Soap is a salt (chemistry), salt of a fatty acid (sometimes other carboxylic acids) used for cleaning and lubricating products as well as other applications. In a domestic setting, soaps, specifically "toilet soaps", are surfactants usually u ...
's
Web Services Description Language
The Web Services Description Language (WSDL ) is an XML-based interface description language that is used for describing the functionality offered by a web service. The acronym is also used for any specific WSDL description of a web service (also ...
s (WSDL), which can also be used to describe
REST
REST (Representational State Transfer) is a software architectural style that was created to describe the design and guide the development of the architecture for the World Wide Web. REST defines a set of constraints for how the architecture of ...
web services.
Format
The service is described using a set of ''
resource
''Resource'' refers to all the materials available in our environment which are Technology, technologically accessible, Economics, economically feasible and Culture, culturally Sustainability, sustainable and help us to satisfy our needs and want ...
'' elements. Each resource contains ''param'' elements to describe the inputs, and ''method'' elements which describe the ''request'' and ''response'' of a resource. The ''request'' element specifies how to represent the input, what types are required and any specific HTTP headers that are required. The ''response'' describes the representation of the service's response, as well as any fault information, to deal with errors.
Example
The following listing shows an example of a WADL description for the Yahoo News Search application.
Generate WADL or generate code from WADL
Java
There are multiple tools to generate java code from an existing WADL:Apache CXF /ref>
*
Apache CXF
Apache CXF is an open source software project developing a Web services framework. It originated as the combination of Celtix developed by IONA Technologies and XFire developed by a team hosted at the now defunct host CodeHaus in 2006. These two ...
OpenAPI Specification
The OpenAPI Specification, previously known as the Swagger Specification, is a Specification (technical standard), specification for a Machine-readable medium, machine-readable interface definition language for describing, producing, consuming and ...