# Jakarta RESTful Web Services

Jakarta RESTful Web Services, (JAX-RS; formerly Java API for RESTful Web Services) is a Jakarta EE API specification that provides support in creating web services according to the Representational State Transfer (REST) architectural pattern. JAX-RS uses annotations, introduced in Java SE 5, to simplify the development and deployment of web service clients and endpoints.
From version 1.1 on, JAX-RS is an official part of Java EE 6. A notable feature of being an official part of Java EE is that no configuration is necessary to start using JAX-RS. For non-Java EE 6 environments a small entry in the web.xml deployment descriptor is required.

## Specification

JAX-RS provides some annotations to aid in mapping a resource class (a POJO) as a web resource. The annotations use the Java package jakarta.ws.rs (previously was javax.ws.rs but was renamed on May 19, 2019). They include:
* @Path specifies the relative path for a resource class or method.
* @GET, @POST, @PUT, @PATCH (since JAX-RS 2.1), @DELETE, @HEAD and @OPTIONS (since JAX-RS 1.1) specify the HTTP request type of a resource.
* @Produces specifies the response Internet media types (used for content negotiation).
* @Consumes specifies the accepted request Internet media types.
In addition, it provides further annotations to method parameters to pull information out of the request. All the @*Param annotations take a key of some form which is used to look up the value required.
* @PathParam binds the method parameter to a path segment.
* @QueryParam binds the method parameter to the value of an HTTP query parameter.
* @MatrixParam binds the method parameter to the value of an HTTP matrix parameter.
* @HeaderParam binds the method parameter to an HTTP header value.
* @CookieParam binds the method parameter to a cookie value.
* @FormParam binds the method parameter to a form value.
* @DefaultValue specifies a default value for the above bindings when the key is not found.
* @Context returns the entire context of the object (for example @Context HttpServletRequest request).

## JAX-RS 2.0

In January 2011 the JCP formed the JSR 339 expert group to work on JAX-RS 2.0. The main targets are (among others) a common client API and support for Hypermedia following the HATEOAS-principle of REST. In May 2013, it reached the Final Release stage.
On 2017-08-22 JAX-RS 2.1 specification final release was published. Main new supported features include server-sent events, reactive clients, and JSON-B.

## Implementations

Implementations of JAX-RS include:
* Apache CXF, an open source Web service framework
* Jersey, the reference implementation from Sun (now Oracle)
* RESTeasy, JBoss's implementation
* Restlet
* WebSphere Application Server from IBM:
** Version 7.0: via the "Feature Pack for Communications Enabled Applications"
** Version 8.0 onwards: natively
* WebLogic Application Server from Oracle, see notes
* Apache Tuscany (http://tuscany.apache.org/documentation-2x/sca-java-bindingrest.html), discontinued
* Cuubez framework (https://web.archive.org/web/20190707005602/http://cuubez.com/)
* Everrest, Codenvy's Implementation
* Jello-Framework, Java Application Framework optimized for Google App Engine, including a powerful RESTful engine and comprehensive Data Authorization model.
* Apache TomEE, an addition to Apache Tomcat