I was messing around with JAX-RS and made an application which calls REST services which produce JSON. I tried Jersey and everything went fine, but I had to switch to RESTEa
Solution: add the following in your web.xml
<context-param>
<param-name>resteasy.servlet.mapping.prefix</param-name>
<param-value>/rest</param-value>
</context-param>
Where /rest is the beginning of your <url-pattern>/rest/*</url-pattern>
(Source: http://docs.jboss.org/resteasy/docs/2.0.0.GA/userguide/html/Installation_Configuration.html#d0e72)
On JBoss AS 7.1 I also had to add to add resteasy.resources ... which is further explained here http://www.javaroots.com/2013/05/creating-rest-services-with-rest-easy.html You may get error like this : Could not find resource for relative : /application/test of full path:... You have to define resteasy.resource context param with the full path of Rest class.