I want to make the current request available to child threads without passing on the original request as method parameters through several layers. The application runs both as a servlet and as a portlet.
Normally, DispatcherServlet and DispatcherPortlet set the current request into a RequestContextHolder on the current thread. That way, a call thread has access to the current request. The request is not propagated to child threads.
In my case, the request spawns a subthread where it makes a ReST call using RestTemplate, and I need to access the original request in an ClientHttpRequestInterceptor that intercepts the RestTemplate. The request that is passed to intercept is useless, I need the original request that hit the server.
Both DispatcherServlet and DispatcherPortlet have a feature to pass on the RequestContext to child threads: setThreadContextInheritable(true). However, it seems not so easy to set that flag to true. There is no init-param which sets it, and usually you specify them in web.xml or portlet.xml.
Is there a way to customize a dispatcher portlet or servlet via their setters using xml configuration? The only way I found is to write a custom dispatcherservlet/portlet which sets the flag to true internally and use that in web.xml and portlet.xml.
There is no way to do this directly through XML configuration. You would need to do as you said and create a subclass of DispatcherServlet which internally calls setThreadContextInheritable(true).
The alternative is to perform your ServletContext configuration in Java. Spring provides a WebApplicationInitializer and a number of useful subtypes where you can register a customized DispatcherServlet (other servlets and filters).
You'd create your instance.
DispatcherServlet servlet = new DispatcherServlet(context);
servlet.setThreadContextInheritable(true);
and then register it
ServletRegistration.Dynamic dispatcher = servletContext.addServlet("dispatcher", servlet);