springcloud Gateway 自定義過濾器例子

springcloud Gateway網關自定義過濾器類型主要分全局和指定路由兩種：
   GlobalFilter：全局過濾器，對所有的路由均起作用
   GatewayFilter：只對指定的路由起作用

GatewayFilter又有兩種實現方式：
一種是直接 實現GatewayFilter, Ordered接口，另一種是 繼承AbstractGatewayFilterFactory類
實現GatewayFilter, Ordered接口方式過濾器：

@Component
public class SignFilter implements GatewayFilter, Ordered {

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        exchange.getResponse().setStatusCode(HttpStatus.OK);
        //exchange.getResponse().getHeaders().add("Content-Type", "application/json;charset=UTF-8");
        ApiResponse result = new ApiResponse();
        
        String sign = exchange.getRequest().getQueryParams().getFirst("sign");
        if(StringUtils.isEmpty(sign)) {
            result.setCode("99");
            result.setMessage("簽名驗證失敗");
            DataBuffer dataBuffer = exchange.getResponse().bufferFactory().wrap(JsonUtil.objToJsonBytes(result));
            return exchange.getResponse().writeWith(Flux.just(dataBuffer));
        }
        return chain.filter(exchange);
    }

    /**過濾器羣執行順序
     * 值越大則優先級越低
     * */
    @Override
    public int getOrder() {
        return 0;
    }
  
}

注入bean：

@SpringBootApplication
public class GateWayApplicationMain {

    public static void main(String[] args) {
        SpringApplication.run(GateWayApplicationMain.class, args);
    }
    
    /**自定義過濾器有兩種實現方式*/
    @Bean
    public RouteLocator routeLocator(RouteLocatorBuilder builder) {
        return builder.routes().route(r ->
                r.path("/sys/**")
                .uri("http://localhost:6320")
                .filters(new SignFilter())
                .id("apiweb"))
            .build();
    }
    
}