Execute some logic at the very end in Webflux WebFilter

Question

In traditional Spring MVC filter I can add some code after chain.doFilter so that they will executed at the very end. For example:

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) {
   chain.doFilter(request, response);
   A();
}

The function A will be executed at the very end after all filters and controllers are executed, even after onBeforeCommitResponse is invoked.

I want to do this same in WebFlux WebFilter.

public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
    return chain.filter(exchange);
    // Call A() after all filters, controllers and after beforeCommit
}

How do I achieve this?

Answer 1

If you want the logic to be executed after all filters and after controller logic finished, you can do something like this:

public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
    return chain.filter(exchange).doFinally(signalType -> {
      //here signalType.toString() is `onComplete`
      System.out.println("After all filters and controller");
      // Call A()
    });
}

Using this in my sample code, produces the following logs (I have 3 webfilters):

2020-07-23 12:35:02.604  INFO c.b.e.i.ImageServiceApplication          :[        ] Starting ImageServiceApplication on in1-1025453mbp with PID 97673 (/Users/Abhi/codes/image-service/out/production/classes started by 1025453 in /Users/Abhi/codes/image-service)
2020-07-23 12:35:02.606  INFO c.b.e.i.ImageServiceApplication          :[        ] No active profile set, falling back to default profiles: default
2020-07-23 12:35:04.142  INFO o.s.b.a.e.web.EndpointLinksResolver      :[        ] Exposing 2 endpoint(s) beneath base path '/actuator'
2020-07-23 12:35:04.461  INFO o.s.b.web.embedded.netty.NettyWebServer  :[        ] Netty started on port(s): 8080
2020-07-23 12:35:04.479  INFO c.b.e.i.ImageServiceApplication          :[        ] Started ImageServiceApplication in 2.134 seconds (JVM running for 2.767)
Executing ScopeCheckFilter
Executing TenancyContextFilter
Executing ImageSizeCheckFilter
2020-07-23 12:36:58.267  INFO c.b.e.i.controller.ImageController       :[tenant1] Request received to generate SAS Token
2020-07-23 12:36:59.722  INFO c.b.e.i.s.a.AzureImageStorageService     :[tenant1] Container exists
2020-07-23 12:36:59.722  INFO c.b.e.i.s.a.AzureImageStorageService     :[tenant1] Generating SAS Token
After all filters