前言

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即使Spring Cloud Gateway自带有许多实用的GatewayFilter Factory、Gateway Filter、Global Filter，但是在很多情景下我们仍然希望可以自定义自己的过滤器。实现一些骚操作。所以自定义过滤器就显得非常有必要。本文主要介绍了自定义Gateway Filter、自定义Global Filter、自定义Gateway Filter Factory。

案例

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实现自己的过滤器我们其实可以去查看Spring Cloud Gateway自带过滤器源码是如何实现的，

自定义Gateway Filter

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实现自定义的Gateway Filter我们需要GatewayFilter、Ordered两个接口

/**
 * 此过滤器功能为计算请求完成时间
 */
public class MyFilter implements GatewayFilter, Ordered {

    private static final String ELAPSED_TIME_BEGIN = "elapsedTimeBegin";

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        exchange.getAttributes().put(ELAPSED_TIME_BEGIN, System.currentTimeMillis());
        return chain.filter(exchange).then(
                Mono.fromRunnable(() -> {
                    Long startTime = exchange.getAttribute(ELAPSED_TIME_BEGIN);
                    if (startTime != null) {
                        System.out.println(exchange.getRequest().getURI().getRawPath() + ": " + (System.currentTimeMillis() - startTime) + "ms");
                    }
                })
        );
    }

    /*
    *过滤器存在优先级，order越大，优先级越低
    */
    @Override
    public int getOrder() {
        return Ordered.LOWEST_PRECEDENCE;
    }
}

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定义好MyFilter以后，其需要跟Route绑定使用，不能在application.yml文件中配置使用

@Bean
    public RouteLocator routeLocator(RouteLocatorBuilder builder) {
        return builder.routes().route(r ->
                r.path("/aa")
                        //转发路由
                        .uri("http://localhost:8003/provider/test")
                        //注册自定义过滤器
                        .filters(new MyFilter())
                        //给定id
                        .id("user-service"))
                .build();
    }
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测试结果：可以在控制台看到请求响应时间。

自定义Gateway Filter Factory

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很多时候我们更希望在配置文件中配置Gateway Filter,所以我们可以自定义过滤器工厂实现。
自定义过滤器工厂需要继承AbstractGatewayFilterFactory

@Component
public class AuthorizeGatewayFilterFactory extends AbstractGatewayFilterFactory<AuthorizeGatewayFilterFactory.Config> {

    private static final Log logger = LogFactory.getLog(AuthorizeGatewayFilterFactory.class);

    private static final String AUTHORIZE_TOKEN = "token";
    private static final String AUTHORIZE_UID = "uid";

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    public AuthorizeGatewayFilterFactory() {
        super(Config.class);
        logger.info("Loaded GatewayFilterFactory [Authorize]");
    }

    @Override
    public List<String> shortcutFieldOrder() {
        return Arrays.asList("enabled");
    }

    @Override
    public GatewayFilter apply(AuthorizeGatewayFilterFactory.Config config) {
        return (exchange, chain) -> {
            if (!config.isEnabled()) {
                return chain.filter(exchange);
            }

            ServerHttpRequest request = exchange.getRequest();
            HttpHeaders headers = request.getHeaders();
            String token = headers.getFirst(AUTHORIZE_TOKEN);
            String uid = headers.getFirst(AUTHORIZE_UID);
            if (token == null) {
                token = request.getQueryParams().getFirst(AUTHORIZE_TOKEN);
            }
            if (uid == null) {
                uid = request.getQueryParams().getFirst(AUTHORIZE_UID);
            }

            ServerHttpResponse response = exchange.getResponse();
            if (StringUtils.isEmpty(token) || StringUtils.isEmpty(uid)) {
                response.setStatusCode(HttpStatus.UNAUTHORIZED);
                return response.setComplete();
            }
            String authToken = stringRedisTemplate.opsForValue().get(uid);
            if (authToken == null || !authToken.equals(token)) {
                response.setStatusCode(HttpStatus.UNAUTHORIZED);
                return response.setComplete();
            }
            return chain.filter(exchange);
        };
    }

    public static class Config {
        // 控制是否开启认证
        private boolean enabled;

        public Config() {}

        public boolean isEnabled() {
            return enabled;
        }

        public void setEnabled(boolean enabled) {
            this.enabled = enabled;
        }
    }
}
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在application.yml配置使用

# 网关路由配置
spring:
  cloud:
    gateway:
      routes:
      - id: user-service
        uri: http://localhost:8077/api/user/list
        predicates:
        - Path=/user/list
        filters:
        # 关键在下面一句，值为true则开启认证，false则不开启
        # 这种配置方式和spring cloud gateway内置的GatewayFilterFactory一致
        - Authorize=true
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自定义Global Filter

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实现自定义全局过滤器需要继承GlobalFilter和Ordered

@Component
public class MyGloablFilter implements GlobalFilter, Ordered {
    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        System.out.println("1111111111111111");
        return chain.filter(exchange);
    }

    @Override
    public int getOrder() {
        return 0;
    }
}
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使用它只需要加上@Component注解