JOnAS is a pure Java, open source, application server conforming to the J2EE specification. However, its high modularity allows to it to be used as

- a J2EE server, for deploying and running EAR applications (i.e. applications composed of both web and ejb components),

- an EJB container, for deploying and running EJB components (e.g. for applications without web interfaces or when using JSP/Servlet engines that are not integrated as a JOnAS J2EE container),

- a Web container, for deploying and running JSPs and Servlets (e.g. for applications without EJB components).