Spring-Cloud-Gateway 初始化，路由模型，以及路由加载等源码在上几篇学习文档中已经描述，接下来来看Spring-Cloud-Gateway是怎么通过这些来对我们的请求进行路由处理的
Spring-Cloud-Gateway整体流程图
image
- DispatcherHandler：所有请求的调度器，负载请求分发
- RoutePredicateHandlerMapping:路由谓语匹配器，用于路由的查找，以及找到路由后返回对应的WebHandler，DispatcherHandler会依次遍历HandlerMapping集合进行处理
- FilteringWebHandler : 使用Filter链表处理请求的WebHandler，RoutePredicateHandlerMapping找到路由后返回对应的FilteringWebHandler对请求进行处理，FilteringWebHandler负责组装Filter链表并调用链表处理请求。
- DispatcherHandler
org.springframework.web.reactive.DispatcherHandler
@Override
public Mono<Void> handle(ServerWebExchange exchange) {
if (logger.isDebugEnabled()) {
ServerHttpRequest request = exchange.getRequest();
logger.debug("Processing " + request.getMethodValue() + " request for [" + request.getURI() + "]");
}
//校验handlerMapping集合是否为空
if (this.handlerMappings == null) {
return Mono.error(HANDLER_NOT_FOUND_EXCEPTION);
}
//依次遍历handlerMapping集合进行请求处理
return Flux.fromIterable(this.handlerMappings)
.concatMap(mapping ->
//通过mapping获取mapping对应的handler
mapping.getHandler(exchange))
.next()
.switchIfEmpty(Mono.error(HANDLER_NOT_FOUND_EXCEPTION))
.flatMap(handler ->
//调用handler处理
invokeHandler(exchange, handler))
.flatMap(result -> handleResult(exchange, result));
}
private Mono<HandlerResult> invokeHandler(ServerWebExchange exchange, Object handler) {
if (this.handlerAdapters != null) {
for (HandlerAdapter handlerAdapter : this.handlerAdapters) {
//判断当前handlerAdapter与handler是否匹配
if (handlerAdapter.supports(handler)) {
return handlerAdapter.handle(exchange, handler);
}
}
}
return Mono.error(new IllegalStateException("No HandlerAdapter: " + handler));
}
DispatcherHandler的handler执行顺序
- 校验handlerMapping
- 遍历Mapping获取mapping对应的handler(此处会找到gateway对应的 RoutePredicateHandlerMapping，并通过 RoutePredicateHandlerMapping获取handler（FilteringWebHandler）)
- 通过handler对应的HandlerAdapter对handler进行调用（gateway使用的 SimpleHandlerAdapter） 即 FilteringWebHandler与SimpleHandlerAdapter对应
org.springframework.web.reactive.result.SimpleHandlerAdapter
public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
WebHandler webHandler = (WebHandler) handler;
//调用handler的handle方法处理请求
Mono<Void> mono = webHandler.handle(exchange);
return mono.then(Mono.empty());
}
- RoutePredicateHandlerMapping
public class RoutePredicateHandlerMapping extends AbstractHandlerMapping {
private final FilteringWebHandler webHandler;
private final RouteLocator routeLocator;
public RoutePredicateHandlerMapping(FilteringWebHandler webHandler, RouteLocator routeLocator) {
this.webHandler = webHandler;
this.routeLocator = routeLocator;
//设置排序字段1，此处的目的是Spring Cloud Gateway 的 GatewayWebfluxEndpoint 提供 HTTP API ，不需要经过网关
//它通过 RequestMappingHandlerMapping 进行请求匹配处理。RequestMappingHandlerMapping 的 order = 0 ，需要排在 RoutePredicateHandlerMapping 前面。所有，RoutePredicateHandlerMapping 设置 order = 1 。
setOrder(1);
}
@Override
protected Mono<?> getHandlerInternal(ServerWebExchange exchange) {
//设置mapping到上下文环境
exchange.getAttributes().put(GATEWAY_HANDLER_MAPPER_ATTR, getClass().getSimpleName());
//查找路由
return lookupRoute(exchange)
// .log("route-predicate-handler-mapping", Level.FINER) //name this
.flatMap((Function<Route, Mono<?>>) r -> {
exchange.getAttributes().remove(GATEWAY_PREDICATE_ROUTE_ATTR);
if (logger.isDebugEnabled()) {
logger.debug("Mapping [" + getExchangeDesc(exchange) + "] to " + r);
}
//将找到的路由信息设置到上下文环境中
exchange.getAttributes().put(GATEWAY_ROUTE_ATTR, r);
//返回mapping对应的WebHandler即FilteringWebHandler
return Mono.just(webHandler);
}).switchIfEmpty(Mono.empty().then(Mono.fromRunnable(() -> {
//当前未找到路由时返回空，并移除GATEWAY_PREDICATE_ROUTE_ATTR
exchange.getAttributes().remove(GATEWAY_PREDICATE_ROUTE_ATTR);
if (logger.isTraceEnabled()) {
logger.trace("No RouteDefinition found for [" + getExchangeDesc(exchange) + "]");
}
})));
}
protected Mono<Route> lookupRoute(ServerWebExchange exchange) {
//通过路由定位器获取路由信息
return this.routeLocator.getRoutes()
.filter(route -> {
// add the current route we are testing
exchange.getAttributes().put(GATEWAY_PREDICATE_ROUTE_ATTR, route.getId());
//返回通过谓语过滤的路由信息
return route.getPredicate().test(exchange);
})
// .defaultIfEmpty() put a static Route not found
// or .switchIfEmpty()
// .switchIfEmpty(Mono.<Route>empty().log("noroute"))
.next()
//TODO: error handling
.map(route -> {
if (logger.isDebugEnabled()) {
logger.debug("Route matched: " + route.getId());
}
//校验路由，目前空实现
validateRoute(route, exchange);
return route;
});
}
}
RoutePredicateHandlerMapping的执行顺序
- 通过路由定位器获取全部路由（RouteLocator）
- 通过路由的谓语（Predicate）过滤掉不可用的路由信息
- 查找到路由信息后将路由信息设置当上下文环境中（GATEWAY_ROUTE_ATTR）
- 返回gatway自定的webhandler（FilteringWebHandler）
备注：
在构建方法中看到setOrder(1);作用：Spring Cloud Gateway 的 GatewayWebfluxEndpoint 提供 HTTP API ，不需要经过网关。
通过 RequestMappingHandlerMapping 进行请求匹配处理。RequestMappingHandlerMapping 的 order = 0 ，需要排在 RoutePredicateHandlerMapping 前面，所以设置 order = 1 。
- FilteringWebHandler
/**
* 通过过滤器处理web请求的处理器
* WebHandler that delegates to a chain of {@link GlobalFilter} instances and
* {@link GatewayFilterFactory} instances then to the target {@link WebHandler}.
*
* @author Rossen Stoyanchev
* @author Spencer Gibb
* @since 0.1
*/
public class FilteringWebHandler implements WebHandler {
protected static final Log logger = LogFactory.getLog(FilteringWebHandler.class);
/**
* 全局过滤器
*/
private final List<GatewayFilter> globalFilters;
public FilteringWebHandler(List<GlobalFilter> globalFilters) {
this.globalFilters = loadFilters(globalFilters);
}
/**
* 包装加载全局的过滤器，将全局过滤器包装成GatewayFilter
* @param filters
* @return
*/
private static List<GatewayFilter> loadFilters(List<GlobalFilter> filters) {
return filters.stream()
.map(filter -> {
//将所有的全局过滤器包装成网关过滤器
GatewayFilterAdapter gatewayFilter = new GatewayFilterAdapter(filter);
//判断全局过滤器是否实现了可排序接口
if (filter instanceof Ordered) {
int order = ((Ordered) filter).getOrder();
//包装成可排序的网关过滤器
return new OrderedGatewayFilter(gatewayFilter, order);
}
return gatewayFilter;
}).collect(Collectors.toList());
}
@Override
public Mono<Void> handle(ServerWebExchange exchange) {
//获取请求上下文设置的路由实例
Route route = exchange.getRequiredAttribute(GATEWAY_ROUTE_ATTR);
//获取路由定义下的网关过滤器集合
List<GatewayFilter> gatewayFilters = route.getFilters();
//组合全局的过滤器与路由配置的过滤器
List<GatewayFilter> combined = new ArrayList<>(this.globalFilters);
//添加路由配置过滤器到集合尾部
combined.addAll(gatewayFilters);
//对过滤器进行排序
//TODO: needed or cached?
AnnotationAwareOrderComparator.sort(combined);
logger.debug("Sorted gatewayFilterFactories: "+ combined);
//创建过滤器链表对其进行链式调用
return new DefaultGatewayFilterChain(combined).filter(exchange);
}
}
FilteringWebHandler的执行顺序
- 构建一个包含全局过滤器的集合（combined）
- 获取上下中的路由信息GATEWAY_ROUTE_ATTR
- 将路由里的过滤器添加到集合中（combined）
- 对过滤器集合进行排序操作
- 通过过滤器集合组装过滤器链表，并进行调用（DefaultGatewayFilterChain与Servlet中的FilterChain与原理是一致的）
- 通过过滤器来处理请求到具体业务服务
整个代码阅读下来，使得对Spring-Cloud-Gateway的工作原理清晰明了的理解。
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