17. Developer Guide

这些是编写网关的一些自定义组件的基本指南。

17.1. 编写自定义路由谓词工厂

为了编写路由谓词，您需要将其实现RoutePredicateFactory为 bean。有一个AbstractRoutePredicateFactory可以扩展的抽象类。

MyRoutePredicateFactory.java

@Component
public class MyRoutePredicateFactory extends AbstractRoutePredicateFactory<MyRoutePredicateFactory.Config> {

    public MyRoutePredicateFactory() {
        super(Config.class);
    }

    @Override
    public Predicate<ServerWebExchange> apply(Config config) {
        // grab configuration from Config object
        return exchange -> {
            //grab the request
            ServerHttpRequest request = exchange.getRequest();
            //take information from the request to see if it
            //matches configuration.
            return matches(config, request);
        };
    }

    public static class Config {
        //Put the configuration properties for your filter here
    }

}

17.2. 编写自定义 GatewayFilter 工厂

要编写GatewayFilter，您必须将其实现GatewayFilterFactory为 bean。您可以扩展一个名为AbstractGatewayFilterFactory. 以下示例显示了如何执行此操作：

示例 73. PreGatewayFilterFactory.java

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

    public PreGatewayFilterFactory() {
        super(Config.class);
    }

    @Override
    public GatewayFilter apply(Config config) {
        // grab configuration from Config object
        return (exchange, chain) -> {
            //If you want to build a "pre" filter you need to manipulate the
            //request before calling chain.filter
            ServerHttpRequest.Builder builder = exchange.getRequest().mutate();
            //use builder to manipulate the request
            return chain.filter(exchange.mutate().request(builder.build()).build());
        };
    }

    public static class Config {
        //Put the configuration properties for your filter here
    }

}

PostGatewayFilterFactory.java

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

    public PostGatewayFilterFactory() {
        super(Config.class);
    }

    @Override
    public GatewayFilter apply(Config config) {
        // grab configuration from Config object
        return (exchange, chain) -> {
            return chain.filter(exchange).then(Mono.fromRunnable(() -> {
                ServerHttpResponse response = exchange.getResponse();
                //Manipulate the response in some way
            }));
        };
    }

    public static class Config {
        //Put the configuration properties for your filter here
    }

}

17.2.1. 在配置中命名自定义过滤器和引用

自定义过滤器类名应以GatewayFilterFactory.

例如，要引用Something配置文件中命名的过滤器，该过滤器必须位于名为SomethingGatewayFilterFactory。

可以创建一个不带 GatewayFilterFactory后缀的网关过滤器，例如class AnotherThing. 此过滤器可以AnotherThing在配置文件中引用。这不是受支持的命名约定，并且在将来的版本中可能会删除此语法。请更新过滤器名称以使其符合要求。

17.3. 编写自定义全局过滤器

要编写自定义全局过滤器，您必须GlobalFilter将接口实现为 bean。这会将过滤器应用于所有请求。

以下示例分别显示了如何设置全局前置和后置过滤器：

@Bean
public GlobalFilter customGlobalFilter() {
    return (exchange, chain) -> exchange.getPrincipal()
        .map(Principal::getName)
        .defaultIfEmpty("Default User")
        .map(userName -> {
          //adds header to proxied request
          exchange.getRequest().mutate().header("CUSTOM-REQUEST-HEADER", userName).build();
          return exchange;
        })
        .flatMap(chain::filter);
}

@Bean
public GlobalFilter customGlobalPostFilter() {
    return (exchange, chain) -> chain.filter(exchange)
        .then(Mono.just(exchange))
        .map(serverWebExchange -> {
          //adds header to response
          serverWebExchange.getResponse().getHeaders().set("CUSTOM-RESPONSE-HEADER",
              HttpStatus.OK.equals(serverWebExchange.getResponse().getStatusCode()) ? "It worked": "It did not work");
          return serverWebExchange;
        })
        .then();
}