Can I use Jersey as both servlet and filter in Spring Boot? - spring-boot

Question

According to Spring documentation:
You can also use a Filter instead of a Servlet by setting spring.jersey.type=filter (in which case the #Bean to replace or override is jerseyFilterRegistration).
According to the answers to this question:
Use a Filter when you want to filter and/or modify requests based on specific conditions. Use a Servlet when you want to control, preprocess and/or postprocess requests.
So what if want to use Jersey with Spring Boot, to both serve json content and apply filters such as checking for authorisation and adding headers to all responses? The spring documentation reads like I have to choose either filter or servlet role for Jersey.
Can I do both with Jersey in a Spring Boot application and if so, how ?

Answer 1

So what if want to use Jersey with Spring Boot, to both serve json content and apply filters such as checking for authorisation and adding headers to all responses?
This question doesn't really make much sense.
Jersey itself is a processing engine. All it needs from the servlet container is the HttpServeltRequest and HttpServletResponse to start processing the request. These can be obtained both as a servlet Filter, or as a servlet HttpServlet. And if you look at the main Jersey servlet container component, ServletContainer, you will see that it both extends HttpServlet and implements Filter.
So being able to configure Jersey as a filter or as a servlet is not anything specific to Spring Boot; Jersey is designed this way. You could configure Jersey as a filter or servlet without Spring Boot.
As far as the filter system, Jersey has it's own filter system, independent of any servlet APIs. But if you want to use servlet filters, there's no reason you can't, whether or not you configure Jersey as a filter or as a servlet. If you understand the servlet filter chain, then you will know that filters get called one after the next, then the servlets are called. So if you want to add a filter and have it perform before the Jersey filter, you can do that. Or if Jersey is a servlet, your filter will be called before the Jersey servlet. Either way it is the same result. Jersey doesn't change any processing behavior just because it is a filter or if is a servlet.
The spring documentation reads like I have to choose either filter or servlet role for Jersey
Yes Servlet or Filter. Should be clear from what I mentioned above. You can have more than one servlet filter. Filters happen one after the other. You can add a filter that has nothing to do with Jersey. They all get passed the same ServletRequest and ServletResponse, so they all interacting with the same request and response. If you want to create a filter to add headers, then do it. It doesn't need to know anything about Jersey.
If you want to create Jersey specific filters (which is independent of any servlet filter mechanisms) for auth/headers and such, you can look at Filters and Interceptors (you can see an auth example in this great answer).
If you want to add servlet filters, then you can do so with FilterRegistrationBeans in Spring Boot.
#Bean
public FilterRegistrationBean anotherFilter() {
}