java - RESTful web service life cycle is *always* per request? -

in beginning java ee 7 antonio goncalves written:

in section writing restful web services -> life cycle , callback:

thus, life cycle of restful web service per request service not have worry concurrency , can use instance variables safely.

yet couple lines later writes:

remember restful web service can annotated @stateless or @singleton benefit services of session beans.

so it? lifecycle per request or can session too?

in addition that, if life cycle session, how handle @context annotation when injecting httpheaders attribute? headers vary during session, attribute updated after each request?

according jax-rs specification, every implementation (like jersey) must support per-request behaviour:

3.1.1 lifecycle , environment

by default new resource class instance created each request resource. first constructor (see section 3.1.2) called, requested dependencies injected (see section 3.2), appropriate method (see section 3.3) invoked , object made available garbage collection.

an implementation may offer other resource class lifecycles, mechanisms specifying these outside scope of specification. e.g. implementation based on inversion-of-control framework may support of lifecycle options provided framework.

this means if resource class not additionally annotated, per-request. 1 well-known exception spring beans: if rest resource spring bean, spring specifies lifecycle of class. same ejbs (@singleton)