Spring: how to pass objects from filters to controllers

Question

I'm trying to add a Filter that creates an object that is then to be used inside a controller in a Spring Boot application.

The idea is to use the Filter as a "centralized" generator of this object - that is request-specific and useful only in a controller. I've tried to use the HttpServletRequest request.getSession().setAttribute method: I can access my object in the controller, but then it will be (clearly) added to the session.

Are the Filters the right way to do so? If yes, where can I keep the temporary object generated by the filter to be used by the controllers?

Answer 1

you can use ServletRequest.setAttribute(String name, Object o);

for example

@RestController
@EnableAutoConfiguration
public class App {

    @RequestMapping("/")
    public String index(HttpServletRequest httpServletRequest) {
        return (String) httpServletRequest.getAttribute(MyFilter.passKey);
    }

    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }

    @Component
    public static class MyFilter implements Filter {

        public static String passKey = "passKey";

        private static String passValue = "hello world";

        @Override
        public void init(FilterConfig filterConfig) throws ServletException {

        }

        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
                throws IOException, ServletException {
            request.setAttribute(passKey, passValue);
            chain.doFilter(request, response);
        }

        @Override
        public void destroy() {

        }
    }
}