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This article is based on Spring-Cloud-Gateway 2.0.x M4

• 1. An overview of the
• 2. DispatcherHandler
  • 2.1 SimpleHandlerAdapter
• 3. RoutePredicateHandlerMapping
• 666. The eggs

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1. An overview of the

This article mainly share RoutePredicateHandlerMapping routing matching.

Let’s take a look at how a request is handled by the Spring Cloud Gateway, as shown below:

1. org.springframework.web.reactive.DispatcherHandler: receives the request, matching HandlerMapping, here will match to the RoutePredicateHandlerMapping.
2. org.springframework.cloud.gateway.handler.RoutePredicateHandlerMapping: Received the request and matched the Route.
3. org.springframework.cloud.gateway.handler.FilteringWebHandler: Obtains the GatewayFilter array of the Route and creates a GatewayFilterChain to process the request.

The first and second steps are shared in this article. The third step is shared in “Spring-Cloud-Gateway source Code Parsing — Processor (3.3) : Creating filter Chains by FilteringWebHandler”.

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2. DispatcherHandler

Org. Springframework. Web. Reactive. DispatcherHandler, request distribution processor, Spring WebFlux access. While this class may be unfamiliar to most of you, let’s see if its Spring MVC sibling, DispatcherServlet, feels a bit familiar.

Here is the DispatcherHandler#handle(ServerWebExchange) method:

1: public class DispatcherHandler implements WebHandler, ApplicationContextAware { 2: 3: @Nullable 4: private List<HandlerMapping> handlerMappings; 5: 6: @Nullable 7: private List<HandlerAdapter> handlerAdapters; 8: 9: @Override 10: public Mono<Void> handle(ServerWebExchange exchange) { 11: if (logger.isDebugEnabled()) { 12: ServerHttpRequest request = exchange.getRequest(); 13: logger.debug("Processing " + request.getMethodValue() + " request for [" + request.getURI() + "]"); 14: } 15: if (this.handlerMappings == null) { 16: return Mono.error(HANDLER_NOT_FOUND_EXCEPTION); 17: } 18: return Flux.fromIterable(this.handlerMappings) 19: .concatMap(mapping -> mapping.getHandler(exchange)) 20: .next() 21: .switchIfEmpty(Mono.error(HANDLER_NOT_FOUND_EXCEPTION)) 22: .flatMap(handler -> invokeHandler(exchange, handler)) 23: .flatMap(result -> handleResult(exchange, result)); 24:25:}}Copy the code

• Lines 18 to 20: Obtain the corresponding WebHandler using handlerMappings in sequence.

  • use#concatMap(Function)The reason for the operator is to considerhandlerMappingsFor details, seeRxJava (4) concatMap operator instructions 。
  • Using officialspring-cloud-gateway-sampleProject, the point of interruption here,handlerMappingsVariable values are shown as follows:
  • In the 【Row 19】, callHandlerMapping#getHandler(ServerWebExchange)Get the Handler. In sorting, RoutePredicateHandlerMapping matching request corresponding Route, and returns FilteringWebHandler. At this point,FilteringWebHandler has not yet obtained the GatewayFilter of the Route, creating a GatewayFilterChain to process the request. This is a bit different from the first figure in this article, which mainly describes the process through which the request goes.
  • Line 21: If no WebHandler is matched, returnHANDLER_NOT_FOUND_EXCEPTION 。

  • Line 22: Call the #handle() method to execute the Handler. The code is as follows:

     1: private Mono<HandlerResult> invokeHandler(ServerWebExchange exchange, Object handler) {
     2: 	if (this.handlerAdapters != null) {
     3: 		for (HandlerAdapter handlerAdapter : this.handlerAdapters) {
     4: 			if (handlerAdapter.supports(handler)) {
     5: 				return handlerAdapter.handle(exchange, handler);
     6: 			}
     7: 		}
     8: 	}
     9: 	return Mono.error(new IllegalStateException("No HandlerAdapter: " + handler));
    10: }Copy the code

    • Using officialspring-cloud-gateway-sampleProject, the point of interruption here,handlerMappingsVariable values are shown as follows:
    • Lines 2 to 8:The orderMatches the HandlerAdapter by callingHandlerAdapter#handle(ServerWebExchange, Object)Method to execute the Handler. At this point, we will match the SimpleHandlerAdapter.
    • Line 9: No HandlerAdapter is matched, return IllegalStateException.

  • Line 23: Call the #handleResult() method to process the result. SimpleHandlerAdapter returns mono.empty (), so this method is not fired. #handleResult() looks like this:

    1: private Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) { 2: return getResultHandler(result).handleResult(exchange, result) 3: .onErrorResume(ex -> result.applyExceptionHandler(ex).flatMap(exceptionResult -> 4: getResultHandler(exceptionResult).handleResult(exchange, exceptionResult))); 5:}Copy the code

2.1 SimpleHandlerAdapter

Org. Springframework. Web. Reactive. Result. SimpleHandlerAdapter, execute WebHandler processor adapter.

The supports(Object) method looks like this:

@Override
public boolean supports(Object handler) {
	return WebHandler.class.isAssignableFrom(handler.getClass());
}Copy the code

• Support WebHandler.

# Handle (ServerWebExchange, Object)

1: @Override 2: public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) { 3: WebHandler webHandler = (WebHandler) handler; 4: Mono<Void> mono = webHandler.handle(exchange); 5: return mono.then(Mono.empty()); 6:}Copy the code

• Lines 3 through 4: callWebHandler#handle(ServerWebExchange)Method, the execution handler. For example,If WebHandler is a FilteringWebHandler, the Route obtains the GatewayFilter array and creates a GatewayFilterChain to process the request.
• Line 5: In WebHandlerAfter the execution ( #then(Mongo)) and returnMono.empty() 。

3. 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; setOrder(1); / / after the RequestMappingHandlerMapping}}Copy the code

1: @Override 2: protected Mono<? > getHandlerInternal(ServerWebExchange exchange) { 3: / / set the GATEWAY_HANDLER_MAPPER_ATTR to RoutePredicateHandlerMapping 4: exchange.getAttributes().put(GATEWAY_HANDLER_MAPPER_ATTR, getClass().getSimpleName()); 5:6: return lookupRoute(exchange) // match Route 7: // .log("route-predicate-handler-mapping", Level.FINER) //name this 8: .flatMap((Function<Route, Mono<? >>) r -> {// Return FilteringWebHandler 9: if (logger.isDebugenabled ()) {10: logger.debug("Mapping [" + getExchangeDesc(exchange) + "] to " + r); 14: exchange.getAttributes().put(GATEWAY_ROUTE_ATTR, r); 15: // Return 16: return mono.just (webHandler); 17:}).switchIfEmpty(mono.empty ().then(mono.fromrunnable (() -> {// if (logger.istraceEnabled ()) {19: logger.trace("No RouteDefinition found for [" + getExchangeDesc(exchange) + "]"); 21:20:}}))); 22:}Copy the code

1: protected Mono<Route> lookupRoute(ServerWebExchange exchange) { 2: return this.routeLocator.getRoutes() 3: .filter(route -> route.getPredicate().test(exchange)) 4: .next() 5: //TODO: error handling 6: .map(route -> { 7: if (logger.isDebugEnabled()) { 8: logger.debug("RouteDefinition matched: " + route.getId()); 9: } 10: validateRoute(route, exchange); 11: return route; 12:}); 13:}Copy the code

666. The eggs

The DispatcherHandler source code for WebFlux.

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