# Upgrading from Resteasy 2 to Resteasy 3

A number of API classes in Resteasy 2, which is based on the JAX-RS 1.1 specification (https://jcp.org/en/jsr/detail?id=311), have been deprecated in, and will eventually be removed from, Resteasy 3, which is based on JAX-RS 2.0 (https://jcp.org/aboutJava/communityprocess/final/jsr339/index.html). For the most part, these changes are due to the fact that a number of facilities specific to Resteasy were introduced in Resteasy 2 and then formalized, in somewhat different form, in JAX-RS 2.0. A few other facilities in Resteasy simply were not carried over to Resteasy 3.

This short document describes the principal changes from Resteasy 2 to Resteasy 3 and gives some hints about upgrading code from the Resteasy 2 API to Resteasy 3. Additional information can be found in the Resteasy Users Guides (http://resteasy.jboss.org/docs.html). A more extensive treatment may be found in the O'Reilly book RESTful Java with JAX-RS 2.0, 2nd Edition, by Bill Burke.

&Client_Framework; &Interceptors; &Asynchronous; &Validation; &Cache; &Miscellaneous;