# How To Pass Context In Standard Way - Without ThreadLocal

javax.transaction.TransactionSynchronizationRegistry holds a Map-like structure and can be used to pass state inside a transaction. It works perfectly since the old J2EE 1.4 days and is thread-independent. Because an Interceptor is executed in the same transaction as the ServiceFacade, the state can be even set in a @AroundInvoke method. The TransactionSynchronizationRegistry (TSR) can be directly injected into an Interceptor:public class CurrentTimeMillisProvider {    @Resource    private TransactionSynchronizationRegistry registry;    @AroundInvoke    public Object injectMap(InvocationContext ic) throws Exception{        registry.putResource(KEY, System.currentTimeMillis());        return ic.proceed();    }} A ServiceFacade don't even has to inject the TSR. The state is automatically propagated to the invoked service:@Stateless@WebService@Interceptors(CurrentTimeMillisProvider.class)public class ServiceFacadeBean implements ServiceFacade {    @EJB    private Service service;    public void performSomeWork(){        service.serviceInvocation();    } }Everything, what is invoked in the scope of a ServiceFacade - and so its transaction has access to the state stored in the injected TSR:@Statelesspublic class ServiceBean implements Service {      @Resource    private TransactionSynchronizationRegistry tsr;    public void serviceInvocation() {        long timeMillis =  (Long)tsr.getResource(KEY);        //...        System.out.println("Content is " + timeMillis);    }} TransactionSynchronizationRegistry works (should work) even in case you had assigned different thread pools to EJBs, which participate in the same transaction. The state would get lost with a simple ThreadLocal.Because we are already in the lightweight Java EE 5 / 6 world - XML and other configuration plumbing are fully optional :-). A deployable, working example (ContextHolder) was tested with Glassfish v3 and NetBeans 6.8m2 and pushed into http://kenai.com/projects/javaee-patterns/.  
[See Context Holder pattern, page 247 in "Real World Java EE Patterns Rethinking Best Practices" book for more in-depth discussion]