聊聊spring cloud gateway的RouteLocator

public interface RouteLocator {

    Flux<Route> getRoutes();
}

@Configuration
@ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true)
@EnableConfigurationProperties
@AutoConfigureBefore(HttpHandlerAutoConfiguration.class)
@AutoConfigureAfter({GatewayLoadBalancerClientAutoConfiguration.class, GatewayClassPathWarningAutoConfiguration.class})
@ConditionalOnClass(DispatcherHandler.class)
public class GatewayAutoConfiguration {
    //......
    @Bean
    public RouteLocatorBuilder routeLocatorBuilder(ConfigurableApplicationContext context) {
        return new RouteLocatorBuilder(context);
    }

    @Bean
    public RouteLocator routeDefinitionRouteLocator(GatewayProperties properties,
                                                   List<GatewayFilterFactory> GatewayFilters,
                                                   List<RoutePredicateFactory> predicates,
                                                   RouteDefinitionLocator routeDefinitionLocator) {
        return new RouteDefinitionRouteLocator(routeDefinitionLocator, predicates, GatewayFilters, properties);
    }

    @Bean
    @Primary
    //TODO: property to disable composite?
    public RouteLocator cachedCompositeRouteLocator(List<RouteLocator> routeLocators) {
        return new CachingRouteLocator(new CompositeRouteLocator(Flux.fromIterable(routeLocators)));
    }

    @Bean
    public RoutePredicateHandlerMapping routePredicateHandlerMapping(FilteringWebHandler webHandler,
                                                                       RouteLocator routeLocator) {
        return new RoutePredicateHandlerMapping(webHandler, routeLocator);
    }

    @Configuration
    @ConditionalOnClass(Health.class)
    protected static class GatewayActuatorConfiguration {

        @Bean
        @ConditionalOnEnabledEndpoint
        public GatewayControllerEndpoint gatewayControllerEndpoint(RouteDefinitionLocator routeDefinitionLocator, List<GlobalFilter> globalFilters,
                                                                List<GatewayFilterFactory> GatewayFilters, RouteDefinitionWriter routeDefinitionWriter,
                                                                RouteLocator routeLocator) {
            return new GatewayControllerEndpoint(routeDefinitionLocator, globalFilters, GatewayFilters, routeDefinitionWriter, routeLocator);
        }
    }
    //......
}

/**
 * {@link RouteLocator} that loads routes from a {@link RouteDefinitionLocator}
 * @author Spencer Gibb
 */
public class RouteDefinitionRouteLocator implements RouteLocator, BeanFactoryAware, ApplicationEventPublisherAware {
    protected final Log logger = LogFactory.getLog(getClass());

    private final RouteDefinitionLocator routeDefinitionLocator;
    private final Map<String, RoutePredicateFactory> predicates = new LinkedHashMap<>();
    private final Map<String, GatewayFilterFactory> gatewayFilterFactories = new HashMap<>();
    private final GatewayProperties gatewayProperties;
    private final SpelExpressionParser parser = new SpelExpressionParser();
    private BeanFactory beanFactory;
    private ApplicationEventPublisher publisher;

    public RouteDefinitionRouteLocator(RouteDefinitionLocator routeDefinitionLocator,
                                       List<RoutePredicateFactory> predicates,
                                       List<GatewayFilterFactory> gatewayFilterFactories,
                                       GatewayProperties gatewayProperties) {
        this.routeDefinitionLocator = routeDefinitionLocator;
        initFactories(predicates);
        gatewayFilterFactories.forEach(factory -> this.gatewayFilterFactories.put(factory.name(), factory));
        this.gatewayProperties = gatewayProperties;
    }

    @Autowired
    private Validator validator;

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.beanFactory = beanFactory;
    }

    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher publisher) {
        this.publisher = publisher;
    }

    private void initFactories(List<RoutePredicateFactory> predicates) {
        predicates.forEach(factory -> {
            String key = factory.name();
            if (this.predicates.containsKey(key)) {
                this.logger.warn("A RoutePredicateFactory named "+ key
                        + " already exists, class: " + this.predicates.get(key)
                        + ". It will be overwritten.");
            }
            this.predicates.put(key, factory);
            if (logger.isInfoEnabled()) {
                logger.info("Loaded RoutePredicateFactory [" + key + "]");
            }
        });
    }

    @Override
    public Flux<Route> getRoutes() {
        return this.routeDefinitionLocator.getRouteDefinitions()
                .map(this::convertToRoute)
                //TODO: error handling
                .map(route -> {
                    if (logger.isDebugEnabled()) {
                        logger.debug("RouteDefinition matched: " + route.getId());
                    }
                    return route;
                });

        /* TODO: trace logging
            if (logger.isTraceEnabled()) {
                logger.trace("RouteDefinition did not match: " + routeDefinition.getId());
            }*/
    }

    //......
}

    private Route convertToRoute(RouteDefinition routeDefinition) {
        Predicate<ServerWebExchange> predicate = combinePredicates(routeDefinition);
        List<GatewayFilter> gatewayFilters = getFilters(routeDefinition);

        return Route.builder(routeDefinition)
                .predicate(predicate)
                .replaceFilters(gatewayFilters)
                .build();
    }

    private Predicate<ServerWebExchange> combinePredicates(RouteDefinition routeDefinition) {
        List<PredicateDefinition> predicates = routeDefinition.getPredicates();
        Predicate<ServerWebExchange> predicate = lookup(routeDefinition, predicates.get(0));

        for (PredicateDefinition andPredicate : predicates.subList(1, predicates.size())) {
            Predicate<ServerWebExchange> found = lookup(routeDefinition, andPredicate);
            predicate = predicate.and(found);
        }

        return predicate;
    }

    private Predicate<ServerWebExchange> lookup(RouteDefinition route, PredicateDefinition predicate) {
        RoutePredicateFactory<Object> factory = this.predicates.get(predicate.getName());
        if (factory == null) {
            throw new IllegalArgumentException("Unable to find RoutePredicateFactory with name " + predicate.getName());
        }
        Map<String, String> args = predicate.getArgs();
        if (logger.isDebugEnabled()) {
            logger.debug("RouteDefinition " + route.getId() + " applying "
                    + args + " to " + predicate.getName());
        }

        Map<String, Object> properties = factory.shortcutType().normalize(args, factory, this.parser, this.beanFactory);
        Object config = factory.newConfig();
        ConfigurationUtils.bind(config, properties,
                factory.shortcutFieldPrefix(), predicate.getName(), validator);
        if (this.publisher != null) {
            this.publisher.publishEvent(new PredicateArgsEvent(this, route.getId(), properties));
        }
        return factory.apply(config);
    }

    private List<GatewayFilter> getFilters(RouteDefinition routeDefinition) {
        List<GatewayFilter> filters = new ArrayList<>();

        //TODO: support option to apply defaults after route specific filters?
        if (!this.gatewayProperties.getDefaultFilters().isEmpty()) {
            filters.addAll(loadGatewayFilters("defaultFilters",
                    this.gatewayProperties.getDefaultFilters()));
        }

        if (!routeDefinition.getFilters().isEmpty()) {
            filters.addAll(loadGatewayFilters(routeDefinition.getId(), routeDefinition.getFilters()));
        }

        AnnotationAwareOrderComparator.sort(filters);
        return filters;
    }

    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;
    }