What is WADL and how to generate them ?

WADL (Web Application Description Language) is an XML description of HTTP based web services.

We can assume it as equivalent to WSDL used in SOAP services.

Format of WADL

Resource is defined with its method (with request and response sub element) element.

param elements defines the inputs with name and type. 

Example

<application ...> 
   <resources base="URL"> 
     <resource path="search"> 
       <method name="GET" id="search"> 
         <request> 
           <param name="id" type="xsd:string" 
             style="query" required="true"/> 
           <param name="start" style="query" type="xsd:int" default="1"/> 
           <param name="sort" style="query" default="name"> 
             <option value="name"/> 
             <option value="city"/> 
           </param> 
           <param name="language" style="query" type="xsd:string" />
         </request>

 
         <response status="200"> 
           <representation mediaType="application/xml" 
             element="shaanns:ResultSet"/> 
         </response> 

         <response status="400"> 
           <representation mediaType="application/xml" 
             element="shaanns:Error"/> 
         </response> 
       </method> 
     </resource> 
   </resources>
 </application>

How to generate WADL or code from WADL ?

In Java, You can use Apache CXF or JAX-RS implementation like, Jersey.

Generate Java code using wadl2java 

wadl2java -o outputDir -p package [-a] [-s jaxrs20] [-c customization]* file.wadl

Example 

wadl2java -o out -p com.shaan.service myservice.wadl

Generate WADL using Jersey

https://github.com/jersey/jersey-1.x/tree/master/samples/generate-wadl

Generate WADL using Spring REST

http://javattitude.com/2014/05/26/wadl-generator-for-spring-rest/