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

Why Don't you use a Bean with the @Scope('request')

@Component
@Scope(value="request", proxyMode= ScopedProxyMode.TARGET_CLASS)
class UserInfo {
   public String getPassword() {
      return password;
   }

   public void setPassword(String password) {
      this.password = password;
   }

   private String password;
}

and then you can Autowireed this bean in both filter and controller to do setting and getting of data.

lifecycle of this UserInfo bean is only exisits within the request so once the http request is done then it terminates the instance as well

Answer 2

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() {

        }
    }
}