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【Java】gateway – 启动

我们从spring.factories开始,主要是GatewayAutoConfiguration,这里主要加载CompositeRouteDefinitionLocator、RouteDefinitionRouteLocator、FilteringWebHandler、RoutePredicateHandlerMapping、RouteRefreshListener、CachingRouteLocator等。
RouteLocator和RouteDefinitionLocator的作用在上一篇已经提过了,FilteringWebHandler、RoutePredicateHandlerMapping这两个等调用的时候讲,这边先知道他们会在这里加载。我们主要看看RouteRefreshListener和CachingRouteLocator。

RouteRefreshListener

RouteRefreshListener实现了ApplicationListener接口,所以他会调用onApplicationEvent方法,在符合某些条件下,会调用reset方法,这个思路和zuul是一样的。所以动态的刷新也可以调用他的事件来触发。

public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ContextRefreshedEvent
|| event instanceof RefreshScopeRefreshedEvent
|| event instanceof InstanceRegisteredEvent) {
reset();
}
else if (event instanceof ParentHeartbeatEvent) {
ParentHeartbeatEvent e = (ParentHeartbeatEvent) event;
resetIfNeeded(e.getValue());
}
else if (event instanceof HeartbeatEvent) {
HeartbeatEvent e = (HeartbeatEvent) event;
resetIfNeeded(e.getValue());
}
}

我们看看reset方法,他其实就是发布了一个RefreshRoutesEvent事件。

private void reset() {
this.publisher.publishEvent(new RefreshRoutesEvent(this));
}

CachingRouteLocator

CachingRouteLocator就是用来接收RefreshRoutesEvent事件的,他实现了ApplicationListener<RefreshRoutesEvent>接口。我们看看他的onApplicationEvent方法。

public void onApplicationEvent(RefreshRoutesEvent event) {
try {
fetch().collect(Collectors.toList()).subscribe(list -> Flux.fromIterable(list)
.materialize().collect(Collectors.toList()).subscribe(signals -> {
applicationEventPublisher
.publishEvent(new RefreshRoutesResultEvent(this));
cache.put(CACHE_KEY, signals);
}, throwable -> handleRefreshError(throwable)));
}
catch (Throwable e) {
handleRefreshError(e);
}
}

他先会调用fetch方法,这里实际上就是调用CompositeRouteLocator#getRoutes,最后再调用RouteDefinitionRouteLocator#getRoutes。

private Flux<Route> fetch() {
return this.delegate.getRoutes().sort(AnnotationAwareOrderComparator.INSTANCE);
}

RouteDefinitionRouteLocator#getRoutes

这个方法可以看到他是获取RouteDefinition的集合,然后再调用convertToRoute方法,在这个方法里,把RouteDefinition转为Route。

@Override
public Flux<Route> getRoutes() {
Flux<Route> routes = this.routeDefinitionLocator.getRouteDefinitions()
.map(this::convertToRoute);
// 其他略
}

RouteDefinitionRouteLocator#convertToRoute

在这里把RouteDefinition转为Route,主要是解析Predicate和GatewayFilter,我们在上一篇已经知道了他会通过工厂类来处理。combinePredicates方法就是处理Predicate的,getFilters是处理Filter的。

private Route convertToRoute(RouteDefinition routeDefinition) {
AsyncPredicate<ServerWebExchange> predicate = combinePredicates(routeDefinition);
List<GatewayFilter> gatewayFilters = getFilters(routeDefinition);
return Route.async(routeDefinition).asyncPredicate(predicate)
.replaceFilters(gatewayFilters).build();
}

RouteDefinitionRouteLocator#combinePredicates

在这里就是把RouteDefinition的predicate转为Route需要的Predicate。这里首先会创建一个Predicate,然后再把剩余的合并,形成了一个left、right的结构。结构图在上一篇已经说过了。
lookup方法就是通过工厂类创建Predicate的地方。

private AsyncPredicate<ServerWebExchange> combinePredicates(
RouteDefinition routeDefinition) {
List<PredicateDefinition> predicates = routeDefinition.getPredicates();
if (predicates == null || predicates.isEmpty()) {
// this is a very rare case, but possible, just match all
return AsyncPredicate.from(exchange -> true);
}
// 创建第一个Predicate
AsyncPredicate<ServerWebExchange> predicate = lookup(routeDefinition,
predicates.get(0));
// 把剩余的进行合并
for (PredicateDefinition andPredicate : predicates.subList(1,
predicates.size())) {
AsyncPredicate<ServerWebExchange> found = lookup(routeDefinition,
andPredicate);
predicate = predicate.and(found);
}
return predicate;
}

RouteDefinitionRouteLocator#lookup

这个方法里,首先先通过配置的名称,获取对应的RoutePredicateFactory,然后组装config信息,最后通过factory.applyAsync创建Predicate。

private AsyncPredicate<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());
}
if (logger.isDebugEnabled()) {
logger.debug("RouteDefinition " + route.getId() + " applying "
+ predicate.getArgs() + " to " + predicate.getName());
}
// @formatter:off
Object config = this.configurationService.with(factory)
.name(predicate.getName())
.properties(predicate.getArgs())
.eventFunction((bound, properties) -> new PredicateArgsEvent(
RouteDefinitionRouteLocator.this, route.getId(), properties))
.bind();
// @formatter:on
return factory.applyAsync(config);
}

RouteDefinitionRouteLocator#getFilters

这个是处理Filter的地方,他主要是通过loadGatewayFilters方法来获取对应的Filter。

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(DEFAULT_FILTERS,
new ArrayList<>(this.gatewayProperties.getDefaultFilters())));
}
if (!routeDefinition.getFilters().isEmpty()) {
filters.addAll(loadGatewayFilters(routeDefinition.getId(),
new ArrayList<>(routeDefinition.getFilters())));
}
AnnotationAwareOrderComparator.sort(filters);
return filters;
}

RouteDefinitionRouteLocator#loadGatewayFilters

这个设计方式跟上面类似,也是通过配置信息的名称,获取对应的GatewayFilterFactory,然后封装configuration信息,通过factory.apply创建一个Filter。

List<GatewayFilter> loadGatewayFilters(String id,
List<FilterDefinition> filterDefinitions) {
ArrayList<GatewayFilter> ordered = new ArrayList<>(filterDefinitions.size());
for (int i = 0; i < filterDefinitions.size(); i++) {
FilterDefinition definition = filterDefinitions.get(i);
GatewayFilterFactory factory = this.gatewayFilterFactories
.get(definition.getName());
if (factory == null) {
throw new IllegalArgumentException(
"Unable to find GatewayFilterFactory with name "
+ definition.getName());
}
if (logger.isDebugEnabled()) {
logger.debug("RouteDefinition " + id + " applying filter "
+ definition.getArgs() + " to " + definition.getName());
}
// @formatter:off
Object configuration = this.configurationService.with(factory)
.name(definition.getName())
.properties(definition.getArgs())
.eventFunction((bound, properties) -> new FilterArgsEvent(
// TODO: why explicit cast needed or java compile fails
RouteDefinitionRouteLocator.this, id, (Map<String, Object>) properties))
.bind();
// @formatter:on
// some filters require routeId
// TODO: is there a better place to apply this?
if (configuration instanceof HasRouteId) {
HasRouteId hasRouteId = (HasRouteId) configuration;
hasRouteId.setRouteId(id);
}
GatewayFilter gatewayFilter = factory.apply(configuration);
if (gatewayFilter instanceof Ordered) {
ordered.add(gatewayFilter);
}
else {
ordered.add(new OrderedGatewayFilter(gatewayFilter, i + 1));
}
}
return ordered;
}

整体流程

【Java】gateway - 启动

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