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title: Custom Filter keywords: [“Custom Filter”] description: custom filter

Description

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

CORS Support

• org.apache.shenyu.web.filter.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.

Filtering Spring Boot health check

• You can control the order by applying @Order to the implementation class .

@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.apache.shenyu.web.filter.AbstractWebFilter

• Add a new class and inherit from org.apache.shenyu.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, While rejecting, it will call method doDenyResponse and sending infos in response body to frontend.