CDI interceptor of HTTP Request and Header params - simple example #javaee7 #cdi #jaxrs

Oct 19, 2015 java cdi english
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While developing and evolving a REST API, using Java EE, there are some cases where you would like to have a look on the incoming HTTP request, specifically the header params, in a more fine grained (per case) way, rather than a Servlet Filter or the more specific ContainerRequestFilters .

One potential way, which I find in some cases very convenient is the addition of CDI interceptors along my JAXRS Resource implementation, that eventually have access to the incoming HTTP request and perform some custom logic. As a developer I can fully control - where (in which paths) to intercept the request, by just adding or removing the custom annotation.With the introduction of Java EE 7, it is easier to mix concerns, so you can easily inject the HTTP Request to plain CDI interceptors.

Below I am just documenting a very simple example, where I use a custom interceptor, to intercept HTTP requests on a business REST API, in order to do some very specific custom Authentication logic. I am checking if the user initiating the request in my REST API is in some specific custom role, that my system defines. Of course the overall example is just an example, but you get the idea.

In order to introduce such a component you need 2 things :

  • introduce a custom annotation, that will be used for activating the interceptor, when it is defined
  • implement the CDI interceptor.
  • apply the annotation, on the paths/ resources of your rest api

The annotation interface. Nothing fancy here, just a custom run-time annotation, so we can use in order to mark specific methods of our JAXRS API.

The implementation of the interceptor

Noteworthy points

  • the interceptor is marked with our custom annotation - simple
  • we @Inject the HttpServletReqest
  • We apply some custom logic, based on the annotation details (I read any params on the definition)
  • From the request I read the header and based on the annotation params I do some basic logic

Applying the interceptor / annotation

Eventually, you can just annotate your @Path JAXRS resources and methods in order to kick in your custom logic

You can find all the files in this very simple sample project on github.