聊聊spring cloud gateway的GatewayFilter

/**
 * Contract for interception-style, chained processing of Web requests that may
 * be used to implement cross-cutting, application-agnostic requirements such
 * as security, timeouts, and others. Specific to a Gateway
 *
 * Copied from WebFilter
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public interface GatewayFilter extends ShortcutConfigurable {

    String NAME_KEY = "name";
    String VALUE_KEY = "value";

    /**
     * Process the Web request and (optionally) delegate to the next
     * {@code WebFilter} through the given {@link GatewayFilterChain}.
     * @param exchange the current server exchange
     * @param chain provides a way to delegate to the next filter
     * @return {@code Mono<Void>} to indicate when request processing is complete
     */
    Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain);

}

public class OrderedGatewayFilter implements GatewayFilter, Ordered {

    private final GatewayFilter delegate;
    private final int order;

    public OrderedGatewayFilter(GatewayFilter delegate, int order) {
        this.delegate = delegate;
        this.order = order;
    }

    public GatewayFilter getDelegate() {
        return delegate;
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        return this.delegate.filter(exchange, chain);
    }

    @Override
    public int getOrder() {
        return this.order;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("OrderedGatewayFilter{");
        sb.append("delegate=").append(delegate);
        sb.append(", order=").append(order);
        sb.append('}');
        return sb.toString();
    }
}

    public class ModifyResponseGatewayFilter implements GatewayFilter, Ordered {
        private final Config config;

        public ModifyResponseGatewayFilter(Config config) {
            this.config = config;
        }

        @Override
        @SuppressWarnings("unchecked")
        public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
            ServerHttpResponseDecorator responseDecorator = new ServerHttpResponseDecorator(exchange.getResponse()) {
                @Override
                public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {

                    ResolvableType inElementType = ResolvableType.forClass(config.getInClass());
                    ResolvableType outElementType = ResolvableType.forClass(config.getOutClass());
                    MediaType contentType = exchange.getResponse().getHeaders().getContentType();
                    Optional<HttpMessageReader<?>> reader = getHttpMessageReader(codecConfigurer, inElementType, contentType);
                    Optional<HttpMessageWriter<?>> writer = getHttpMessageWriter(codecConfigurer, outElementType, null);

                    if (reader.isPresent() && writer.isPresent()) {

                        ResponseAdapter responseAdapter = new ResponseAdapter(body, getDelegate().getHeaders());

                        Flux<?> modified = reader.get().read(inElementType, responseAdapter, config.getInHints())
                                .cast(inElementType.resolve())
                                .flatMap(originalBody -> Flux.just(config.rewriteFunction.apply(exchange, originalBody)))
                                .cast(outElementType.resolve());

                        return getDelegate().writeWith(
                                writer.get().write((Publisher)modified, outElementType, null, getDelegate(),
                                        config.getOutHints())
                        );

                    }
                    // TODO: error? log?

                    return getDelegate().writeWith(body);
                }

                @Override
                public Mono<Void> writeAndFlushWith(Publisher<? extends Publisher<? extends DataBuffer>> body) {
                    return writeWith(Flux.from(body)
                            .flatMapSequential(p -> p));
                }
            };

            return chain.filter(exchange.mutate().response(responseDecorator).build());
        }

        @Override
        public int getOrder() {
            return NettyWriteResponseFilter.WRITE_RESPONSE_FILTER_ORDER - 1;
        }

    }

    private static class GatewayFilterAdapter implements GatewayFilter {

        private final GlobalFilter delegate;

        public GatewayFilterAdapter(GlobalFilter delegate) {
            this.delegate = delegate;
        }

        @Override
        public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
            return this.delegate.filter(exchange, chain);
        }

        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder("GatewayFilterAdapter{");
            sb.append("delegate=").append(delegate);
            sb.append('}');
            return sb.toString();
        }
    }

@FunctionalInterface
public interface GatewayFilterFactory<C> extends ShortcutConfigurable, Configurable<C> {

    String NAME_KEY = "name";
    String VALUE_KEY = "value";

    // useful for javadsl
    default GatewayFilter apply(Consumer<C> consumer) {
        C config = newConfig();
        consumer.accept(config);
        return apply(config);
    }

    default Class<C> getConfigClass() {
        throw new UnsupportedOperationException("getConfigClass() not implemented");
    }

    @Override
    default C newConfig() {
        throw new UnsupportedOperationException("newConfig() not implemented");
    }

    GatewayFilter apply(C config);

    default String name() {
        //TODO: deal with proxys
        return NameUtils.normalizeFilterFactoryName(getClass());
    }

    @Deprecated
    default ServerHttpRequest.Builder mutate(ServerHttpRequest request) {
        return request.mutate();
    }
}

public abstract class AbstractGatewayFilterFactory<C>
        extends AbstractConfigurable<C> implements GatewayFilterFactory<C> {

    @SuppressWarnings("unchecked")
    public AbstractGatewayFilterFactory() {
        super((Class<C>) Object.class);
    }

    public AbstractGatewayFilterFactory(Class<C> configClass) {
        super(configClass);
    }

    public static class NameConfig {
        private String name;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }
    }
}

public abstract class AbstractNameValueGatewayFilterFactory extends AbstractGatewayFilterFactory<AbstractNameValueGatewayFilterFactory.NameValueConfig> {

    public AbstractNameValueGatewayFilterFactory() {
        super(NameValueConfig.class);
    }

    public List<String> shortcutFieldOrder() {
        return Arrays.asList(GatewayFilter.NAME_KEY, GatewayFilter.VALUE_KEY);
    }

    @Validated
    public static class NameValueConfig {
        @NotEmpty
        protected String name;
        @NotEmpty
        protected String value;

        public String getName() {
            return name;
        }

        public NameValueConfig setName(String name) {
            this.name = name;
            return this;
        }

        public String getValue() {
            return value;
        }

        public NameValueConfig setValue(String value) {
            this.value = value;
            return this;
        }

        @Override
        public String toString() {
            return new ToStringCreator(this)
                    .append("name", name)
                    .append("value", value)
                    .toString();
        }
    }
}

/**
 * This filter changes the request uri by
 * {@link #determineRequestUri(ServerWebExchange, T)} logic.
 *
 * @author Toshiaki Maki
 */
public abstract class AbstractChangeRequestUriGatewayFilterFactory<T>
        extends AbstractGatewayFilterFactory<T> {
    private final int order;

    public AbstractChangeRequestUriGatewayFilterFactory(Class<T> clazz, int order) {
        super(clazz);
        this.order = order;
    }

    public AbstractChangeRequestUriGatewayFilterFactory(Class<T> clazz) {
        this(clazz, RouteToRequestUrlFilter.ROUTE_TO_URL_FILTER_ORDER + 1);
    }

    protected abstract Optional<URI> determineRequestUri(ServerWebExchange exchange,
            T config);

    public GatewayFilter apply(T config) {
        return new OrderedGatewayFilter((exchange, chain) -> {
            Optional<URI> uri = this.determineRequestUri(exchange, config);
            uri.ifPresent(u -> {
                Map<String, Object> attributes = exchange.getAttributes();
                attributes.put(GATEWAY_REQUEST_URL_ATTR, u);
            });
            return chain.filter(exchange);
        }, this.order);
    }
}

    private List<GatewayFilter> loadGatewayFilters(String id, List<FilterDefinition> filterDefinitions) {
        List<GatewayFilter> filters = filterDefinitions.stream()
                .map(definition -> {
                    GatewayFilterFactory factory = this.gatewayFilterFactories.get(definition.getName());
                    if (factory == null) {
                        throw new IllegalArgumentException("Unable to find GatewayFilterFactory with name " + definition.getName());
                    }
                    Map<String, String> args = definition.getArgs();
                    if (logger.isDebugEnabled()) {
                        logger.debug("RouteDefinition " + id + " applying filter " + args + " to " + definition.getName());
                    }

                    Map<String, Object> properties = factory.shortcutType().normalize(args, factory, this.parser, this.beanFactory);

                    Object configuration = factory.newConfig();

                    ConfigurationUtils.bind(configuration, properties,
                            factory.shortcutFieldPrefix(), definition.getName(), validator);

                    GatewayFilter gatewayFilter = factory.apply(configuration);
                    if (this.publisher != null) {
                        this.publisher.publishEvent(new FilterArgsEvent(this, id, properties));
                    }
                    return gatewayFilter;
                })
                .collect(Collectors.toList());

        ArrayList<GatewayFilter> ordered = new ArrayList<>(filters.size());
        for (int i = 0; i < filters.size(); i++) {
            GatewayFilter gatewayFilter = filters.get(i);
            if (gatewayFilter instanceof Ordered) {
                ordered.add(gatewayFilter);
            }
            else {
                ordered.add(new OrderedGatewayFilter(gatewayFilter, i + 1));
            }
        }

        return ordered;
    }