Core Integration

/**
 * Main filter that integrates Sentinel flow control with Spring Cloud Gateway
 * Implements GatewayFilter, GlobalFilter, and Ordered interfaces
 */
public class SentinelGatewayFilter implements GatewayFilter, GlobalFilter, Ordered {
    /**
     * Default constructor with highest precedence order
     */
    public SentinelGatewayFilter();
    
    /**
     * Constructor with custom order
     * @param order - Filter execution order
     */
    public SentinelGatewayFilter(int order);
    
    /**
     * Constructor with custom request item parser
     * @param serverWebExchangeItemParser - Custom parser for request parameters
     */
    public SentinelGatewayFilter(RequestItemParser<ServerWebExchange> serverWebExchangeItemParser);
    
    /**
     * Full constructor with custom order and parser
     * @param order - Filter execution order
     * @param requestItemParser - Custom parser for request parameters
     */
    public SentinelGatewayFilter(int order, RequestItemParser<ServerWebExchange> requestItemParser);
    
    /**
     * Filter method for request processing with Sentinel integration
     * @param exchange - Server web exchange
     * @param chain - Gateway filter chain
     * @return Mono<Void> representing completion
     */
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain);
    
    /**
     * Returns filter execution order
     * @return int order value
     */
    public int getOrder();
    
}

// Basic usage with default configuration
@Bean
@Order(-1)
public GlobalFilter sentinelGatewayFilter() {
    return new SentinelGatewayFilter();
}

// Custom order
@Bean
@Order(100)
public GlobalFilter sentinelGatewayFilter() {
    return new SentinelGatewayFilter(100);
}

// Custom request parser
@Bean
@Order(-1)
public GlobalFilter sentinelGatewayFilter() {
    CustomRequestItemParser parser = new CustomRequestItemParser();
    return new SentinelGatewayFilter(parser);
}

/**
 * Exception handler for Sentinel block exceptions in reactive environment
 * Implements WebExceptionHandler interface
 */
public class SentinelGatewayBlockExceptionHandler implements WebExceptionHandler {
    /**
     * Constructor with Spring WebFlux components
     * @param viewResolvers - List of view resolvers for rendering responses
     * @param serverCodecConfigurer - Server codec configurer for message writers
     */
    public SentinelGatewayBlockExceptionHandler(List<ViewResolver> viewResolvers, ServerCodecConfigurer serverCodecConfigurer);
    
    /**
     * Handles exceptions, specifically Sentinel block exceptions
     * @param exchange - Server web exchange
     * @param ex - Exception to handle
     * @return Mono<Void> representing completion
     */
    public Mono<Void> handle(ServerWebExchange exchange, Throwable ex);
}

@Configuration
public class GatewayConfiguration {

    private final List<ViewResolver> viewResolvers;
    private final ServerCodecConfigurer serverCodecConfigurer;

    public GatewayConfiguration(ObjectProvider<List<ViewResolver>> viewResolversProvider,
                                ServerCodecConfigurer serverCodecConfigurer) {
        this.viewResolvers = viewResolversProvider.getIfAvailable(Collections::emptyList);
        this.serverCodecConfigurer = serverCodecConfigurer;
    }

    @Bean
    @Order(-1)
    public SentinelGatewayBlockExceptionHandler sentinelGatewayBlockExceptionHandler() {
        return new SentinelGatewayBlockExceptionHandler(viewResolvers, serverCodecConfigurer);
    }
}