Filter Extension

Description

• This doc shows a demo for how to extend org.springframework.web.server.WebFliter.

CORS Support

• org.dromara.soul.bootstrap.cors.CrossFilter is designed for WebFilter implementation.

  public class CrossFilter implements WebFilter {
      private static final String ALLOWED_HEADERS = "x-requested-with, authorization, Content-Type, Authorization, credential, X-XSRF-TOKEN,token,username,client";
      private static final String ALLOWED_METHODS = "*";
      private static final String ALLOWED_ORIGIN = "*";
      private static final String ALLOWED_EXPOSE = "*";
      private static final String MAX_AGE = "18000";
      @Override    @SuppressWarnings("all")    public Mono<Void> filter(final ServerWebExchange exchange, final WebFilterChain chain) {        ServerHttpRequest request = exchange.getRequest();        if (CorsUtils.isCorsRequest(request)) {            ServerHttpResponse response = exchange.getResponse();            HttpHeaders headers = response.getHeaders();            headers.add("Access-Control-Allow-Origin", ALLOWED_ORIGIN);            headers.add("Access-Control-Allow-Methods", ALLOWED_METHODS);            headers.add("Access-Control-Max-Age", MAX_AGE);            headers.add("Access-Control-Allow-Headers", ALLOWED_HEADERS);            headers.add("Access-Control-Expose-Headers", ALLOWED_EXPOSE);            headers.add("Access-Control-Allow-Credentials", "true");            if (request.getMethod() == HttpMethod.OPTIONS) {                response.setStatusCode(HttpStatus.OK);                return Mono.empty();            }        }        return chain.filter(exchange);    }}

* Registering CrossFilter as a Spring Bean and you are ready to go.
## Filtering Spring Boot health check
* You can control the order by applying `@Order` to the implementation class .
```java@Component@Order(-99)public final class HealthFilter implements WebFilter {
    private static final String[] FILTER_TAG = {"/actuator/health", "/health_check"};
    @Override    public Mono<Void> filter(@Nullable final ServerWebExchange exchange, @Nullable final WebFilterChain chain) {        ServerHttpRequest request = Objects.requireNonNull(exchange).getRequest();        String urlPath = request.getURI().getPath();        for (String check : FILTER_TAG) {            if (check.equals(urlPath)) {                String result = JsonUtils.toJson(new Health.Builder().up().build());                DataBuffer dataBuffer = exchange.getResponse().bufferFactory().wrap(result.getBytes());                return exchange.getResponse().writeWith(Mono.just(dataBuffer));            }        }        return Objects.requireNonNull(chain).filter(exchange);    }}

Extending org.dromara.soul.web.filter.AbstractWebFilter

• Add a new class and inherit from org.dromara.soul.web.filter.AbstractWebFilter.
• Implement abstract methods of parent class.

   /**     * this is Template Method ,children Implement your own filtering logic.     *     * @param exchange the current server exchange     * @param chain    provides a way to delegate to the next filter     * @return {@code Mono<Boolean>} result：TRUE (is pass)，and flow next filter；FALSE (is not pass) execute doDenyResponse(ServerWebExchange exchange)     */    protected abstract Mono<Boolean> doFilter(ServerWebExchange exchange, WebFilterChain chain);
    /**     * this is Template Method ,children Implement your own And response client.     *     * @param exchange the current server exchange.     * @return {@code Mono<Void>} response msg.     */    protected abstract Mono<Void> doDenyResponse(ServerWebExchange exchange);

• if method doFilter returns Mono true, this filter is passing, but not vice versa. While rejecting, it will call method doDenyResponse and sending infos in response body to frontend.