Spring Cloud Gateway 源码剖析之Predicate谓词详解
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2021-04-04 08:41
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一、前言
我们上一篇 Spring Cloud Gateway 源码剖析之Route数据模型 中讲到了 Route 数据模型，其中有 Predicate 属性。
这一篇我们就来讲一讲 Predicate 谓词相关源码。Predicate 对象是由 RoutePredicateFactory 工厂类创建，那我们就来看下 RoutePredicateFactory 是如何创建 Predicate 的。
二、RoutePredicateFactory
从上图可知
#name() 默认方法，调用 NameUtils#normalizePredicateName(Class) 方法，获得 RoutePredicateFactory 的名字。该方法截取类名前半段，例如 QueryRoutePredicateFactory 的结果为 Query 。
#apply() 接口方法，创建 Predicate 。
可以直接看到处理器类与相关谓词工厂类如下
这里再对相关谓词工厂进行分类：
2.1 AfterRoutePredicateFactory
Route 匹配 ：请求时间满足在配置时间之后
配置：
spring:
cloud:
gateway:
routes:
- id: after_route
uri: http://example.org
predicates:
- After=2017-01-20T17:42:47.789-07:00[America/Denver]代码：
public Predicate<ServerWebExchange> apply(AfterRoutePredicateFactory.Config config) {
ZonedDateTime datetime = config.getDatetime();
return (exchange) -> {
ZonedDateTime now = ZonedDateTime.now();
return now.isAfter(datetime);
};
}
2.2 BeforeRoutePredicateFactory
Route 匹配 ：请求时间满足在配置时间之前
配置：
spring:
cloud:
gateway:
routes:
- id: before_route
uri: http://example.org
predicates:
- Before=2017-01-20T17:42:47.789-07:00[America/Denver]代码：
public Predicate<ServerWebExchange> apply(BeforeRoutePredicateFactory.Config config) {
ZonedDateTime datetime = config.getDatetime();
return (exchange) -> {
ZonedDateTime now = ZonedDateTime.now();
return now.isBefore(datetime);
};
}
2.3 BetweenRoutePredicateFactory
Route 匹配 ：请求时间满足在配置时间之间
配置：
spring:
cloud:
gateway:
routes:
- id: between_route
uri: http://example.org
predicates:
- Betweeen=2017-01-20T17:42:47.789-07:00[America/Denver], 2017-01-21T17:42:47.789-07:00[America/Denver]代码：
public Predicate<ServerWebExchange> apply(BetweenRoutePredicateFactory.Config config) {
ZonedDateTime datetime1 = config.datetime1;
ZonedDateTime datetime2 = config.datetime2;
Assert.isTrue(datetime1.isBefore(datetime2), config.datetime1 + " must be before " + config.datetime2);
return (exchange) -> {
ZonedDateTime now = ZonedDateTime.now();
return now.isAfter(datetime1) && now.isBefore(datetime2);
};
}
2.4 CookieRoutePredicateFactory
Route 匹配 ：请求指定 Cookie 正则匹配指定值
配置：
spring:
cloud:
gateway:
routes:
- id: cookie_route
uri: http://example.org
predicates:
- Cookie=chocolate, ch.p代码：
public Predicate<ServerWebExchange> apply(CookieRoutePredicateFactory.Config config) {return (exchange) -> {List<HttpCookie> cookies = (List)exchange.getRequest().getCookies().get(config.name);if (cookies == null) {return false;} else {Iterator var3 = cookies.iterator();HttpCookie cookie;do {if (!var3.hasNext()) {return false;}cookie = (HttpCookie)var3.next();} while(!cookie.getValue().matches(config.regexp));return true;}};}
2.5 HeaderRoutePredicateFactory
Route 匹配 ：请求头满足匹配
配置：
spring:
cloud:
gateway:
routes:
- id: header_route
uri: http://example.org
predicates:
- Header=X-Request-Id, \d+代码：
public Predicate<ServerWebExchange> apply(HeaderRoutePredicateFactory.Config config) {
boolean hasRegex = !StringUtils.isEmpty(config.regexp);
return (exchange) -> {
List<String> values = (List)exchange.getRequest().getHeaders().getOrDefault(config.header, Collections.emptyList());
if (values.isEmpty()) {
return false;
} else {
return hasRegex ? values.stream().anyMatch((value) -> {
return value.matches(config.regexp);
}) : true;
}
};
}
2.6 HostRoutePredicateFactory
Route 匹配 ：请求 Host 匹配指定值
配置：
spring:
cloud:
gateway:
routes:
- id: host_route
uri: http://example.org
predicates:
- Host=**.somehost.org代码：
public Predicate<ServerWebExchange> apply(HostRoutePredicateFactory.Config config) {
return (exchange) -> {
String host = exchange.getRequest().getHeaders().getFirst("Host");
Optional<String> optionalPattern = config.getPatterns().stream().filter((pattern) -> {
return this.pathMatcher.match(pattern, host);
}).findFirst();
if (optionalPattern.isPresent()) {
Map<String, String> variables = this.pathMatcher.extractUriTemplateVariables((String)optionalPattern.get(), host);
ServerWebExchangeUtils.putUriTemplateVariables(exchange, variables);
return true;
} else {
return false;
}
};
}
2.7 MethodRoutePredicateFactory
Route 匹配 ：请求 Method 匹配指定值
配置：
spring:
cloud:
gateway:
routes:
- id: method_route
uri: http://example.org
predicates:
- Method=GET代码：
public Predicate<ServerWebExchange> apply(MethodRoutePredicateFactory.Config config) {
return (exchange) -> {
HttpMethod requestMethod = exchange.getRequest().getMethod();
return requestMethod == config.getMethod();
};
}
2.8 PathRoutePredicateFactory
Route 匹配 ：请求 Path 匹配指定值
配置：
spring:
cloud:
gateway:
routes:
- id: host_route
uri: http://example.org
predicates:
- Path=/foo/{segment}代码：
public Predicate<ServerWebExchange> apply(PathRoutePredicateFactory.Config config) {ArrayList<PathPattern> pathPatterns = new ArrayList();synchronized(this.pathPatternParser) {this.pathPatternParser.setMatchOptionalTrailingSeparator(config.isMatchOptionalTrailingSeparator());config.getPatterns().forEach((pattern) -> {PathPattern pathPattern = this.pathPatternParser.parse(pattern);pathPatterns.add(pathPattern);});}return (exchange) -> {PathContainer path = PathContainer.parsePath(exchange.getRequest().getURI().getPath());Optional<PathPattern> optionalPathPattern = pathPatterns.stream().filter((pattern) -> {return pattern.matches(path);}).findFirst();if (optionalPathPattern.isPresent()) {PathPattern pathPattern = (PathPattern)optionalPathPattern.get();traceMatch("Pattern", pathPattern.getPatternString(), path, true);PathMatchInfo pathMatchInfo = pathPattern.matchAndExtract(path);ServerWebExchangeUtils.putUriTemplateVariables(exchange, pathMatchInfo.getUriVariables());return true;} else {traceMatch("Pattern", config.getPatterns(), path, false);return false;}};}
2.9 QueryRoutePredicateFactory
Route 匹配 ：请求 QueryParam 匹配指定值
配置：
spring:
cloud:
gateway:
routes:
- id: query_route
uri: http://example.org
predicates:
- Query=baz
- Query=foo, ba.代码：
public Predicate<ServerWebExchange> apply(QueryRoutePredicateFactory.Config config) {return (exchange) -> {if (!StringUtils.hasText(config.regexp)) {return exchange.getRequest().getQueryParams().containsKey(config.param);} else {List<String> values = (List)exchange.getRequest().getQueryParams().get(config.param);if (values == null) {return false;} else {Iterator var3 = values.iterator();String value;do {if (!var3.hasNext()) {return false;}value = (String)var3.next();} while(value == null || !value.matches(config.regexp));return true;}}};}
2.10 RemoteAddrRoutePredicateFactory
Route 匹配 ：请求来源 IP 在指定范围内
配置：
spring:
cloud:
gateway:
routes:
- id: remoteaddr_route
uri: http://example.org
predicates:
- RemoteAddr=192.168.1.1/24代码：
public Predicate<ServerWebExchange> apply(RemoteAddrRoutePredicateFactory.Config config) {List<IpSubnetFilterRule> sources = this.convert(config.sources);return (exchange) -> {InetSocketAddress remoteAddress = config.remoteAddressResolver.resolve(exchange);if (remoteAddress != null && remoteAddress.getAddress() != null) {String hostAddress = remoteAddress.getAddress().getHostAddress();String host = exchange.getRequest().getURI().getHost();if (log.isDebugEnabled() && !hostAddress.equals(host)) {log.debug("Remote addresses didn't match " + hostAddress + " != " + host);}Iterator var6 = sources.iterator();while(var6.hasNext()) {IpSubnetFilterRule source = (IpSubnetFilterRule)var6.next();if (source.matches(remoteAddress)) {return true;}}}return false;};}
三、RoutePredicateHandlerMapping
我们先来看下 Spring Cloud Gateway 官网提供的架构图：
上一节讲完了常见分类的 Predicate 匹配规则，客户端发送请求过来，通过 HandlerMapping 进行 predicate 的匹配，匹配成功再进行下面的处理。
3.1 org.springframework.web.reactive.DispatcherHandler
接收到请求，匹配 HandlerMapping ，此处会匹配到 RoutePredicateHandlerMapping。由于 Gateway 是构建在 reactive 上的，所以这边的 web 类型就是 reactive。
public class DispatcherHandler implements WebHandler, ApplicationContextAware {
private static final Exception HANDLER_NOT_FOUND_EXCEPTION;
@Nullable
private List<HandlerMapping> handlerMappings;
@Nullable
private List<HandlerAdapter> handlerAdapters;
@Nullable
private List<HandlerResultHandler> resultHandlers;
public Mono<Void> handle(ServerWebExchange exchange) {
return this.handlerMappings == null ? this.createNotFoundError() :
// 顺序使用 handlerMappings 获得对应的 WebHandler
Flux.fromIterable(this.handlerMappings).concatMap((mapping) -> {
// 获得 Handler
return mapping.getHandler(exchange);
// 如果匹配不到 WebHandler ，返回 HANDLER_NOT_FOUND_EXCEPTION 。
}).next().switchIfEmpty(this.createNotFoundError()).flatMap((handler) -> {
// 调用 invokeHandler() 方法，执行 Handler 。
return this.invokeHandler(exchange, handler);
}).flatMap((result) -> {
// 调用 handleResult() 方法，处理结果
return this.handleResult(exchange, result);
});
}
...
}
继续跟一下 invokeHandler() 方法：
private Mono<HandlerResult> invokeHandler(ServerWebExchange exchange, Object handler) {
if (this.handlerAdapters != null) {
// 获取Adapters， WebHandler 的处理器适配器。
Iterator var3 = this.handlerAdapters.iterator();
while(var3.hasNext()) {
HandlerAdapter handlerAdapter = (HandlerAdapter)var3.next();
// 调用support方法 ，是否支持 WebHandler
if (handlerAdapter.supports(handler)) {
// 调用handle 方法，执行处理器
return handlerAdapter.handle(exchange, handler);
}
}
}
return Mono.error(new IllegalStateException("No HandlerAdapter: " + handler));
}
public boolean supports(Object handler) {
return WebHandler.class.isAssignableFrom(handler.getClass());
}
public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
WebHandler webHandler = (WebHandler)handler;
// 执行处理器。例如，WebHandler 为 FilteringWebHandler 时，获得 Route 的 GatewayFilter 数组，创建 GatewayFilterChain 处理请求。
Mono<Void> mono = webHandler.handle(exchange);
// 在 WebHandler 执行完后 #then(Mongo)，然后返回 Mono.empty() 。
return mono.then(Mono.empty());
}
SimpleHandlerAdapter 返回的是 Mono.empty() ，所以不会触发该方法。
private Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {
return this.getResultHandler(result).handleResult(exchange, result).onErrorResume((ex) -> {
return result.applyExceptionHandler(ex).flatMap((exceptionResult) -> {
return this.getResultHandler(exceptionResult).handleResult(exchange, exceptionResult);
});
});
}
3.2 org.springframework.cloud.gateway.handler.RoutePredicateHandlerMapping
接收到请求，匹配 Route ，并返回处理 Route 的 FilteringWebHandler。
SimpleHandlerAdapter#handle(ServerWebExchange, Object) 调用 FilteringWebHandler#handle(ServerWebExchange) 方法，处理请求。
public class RoutePredicateHandlerMapping extends AbstractHandlerMapping {
private final FilteringWebHandler webHandler;
private final RouteLocator routeLocator;
private final Integer managmentPort;
public RoutePredicateHandlerMapping(FilteringWebHandler webHandler, RouteLocator routeLocator, GlobalCorsProperties globalCorsProperties, Environment environment) {
this.webHandler = webHandler;
this.routeLocator = routeLocator;
if (environment.containsProperty("management.server.port")) {
this.managmentPort = new Integer(environment.getProperty("management.server.port"));
} else {
this.managmentPort = null;
}
// RequestMappingHandlerMapping 之后
this.setOrder(1);
this.setCorsConfigurations(globalCorsProperties.getCorsConfigurations());
}
protected Mono<?> getHandlerInternal(ServerWebExchange exchange) {
if (this.managmentPort != null && exchange.getRequest().getURI().getPort() == this.managmentPort) {
return Mono.empty();
} else {
// 设置 GATEWAY_HANDLER_MAPPER_ATTR 为
RoutePredicateHandlerMappingexchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_HANDLER_MAPPER_ATTR, this.getSimpleName());
// 匹配路由
return this.lookupRoute(exchange).flatMap((r) -> {
exchange.getAttributes().remove(ServerWebExchangeUtils.GATEWAY_PREDICATE_ROUTE_ATTR);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Mapping [" + this.getExchangeDesc(exchange) + "] to " + r);
}
// 设置 GATEWAY_ROUTE_ATTR 为 匹配的 Route
exchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR, r);
return Mono.just(this.webHandler);
}).switchIfEmpty(Mono.empty().then(Mono.fromRunnable(() -> { //匹配不到返回
exchange.getAttributes().remove(ServerWebExchangeUtils.GATEWAY_PREDICATE_ROUTE_ATTR);
if (this.logger.isTraceEnabled()) {
this.logger.trace("No RouteDefinition found for [" + this.getExchangeDesc(exchange) + "]");
}
})));
}
}
}
跟一下 lookupRoute 匹配路由，这个方法是网关的核心，像我们自研的网关，如果你刚接手公司中的网关项目，找到匹配路由再展开，能帮你省很多时间，快速熟悉公司中网关的项目。
protected Mono<Route> lookupRoute(ServerWebExchange exchange) {
// 获取所有路由
return this.routeLocator.getRoutes().concatMap((route) -> {
return Mono.just(route).filterWhen((r) -> {
exchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_PREDICATE_ROUTE_ATTR, r.getId());
// 并调用 Predicate#apply(ServerWebExchange) 方法，顺序匹配一个 Route。
return (Publisher)r.getPredicate().apply(exchange);
// 未来会增加匹配过程中发生异常的处理。目前，任何一个 Predicate#test(ServerWebExchange) 的方法调用发生异常时，都会导致匹配不到 Route。一定要注意。
}).doOnError((e) -> {
this.logger.error("Error applying predicate for route: " + route.getId(), e);
}).onErrorResume((e) -> {
return Mono.empty();
});
}).next().map((route) -> {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Route matched: " + route.getId());
}
this.validateRoute(route, exchange);
return route;
});
}
3.3 org.springframework.cloud.gateway.handler.FilteringWebHandler
获得 Route 的 GatewayFilter 数组，创建 GatewayFilterChain 处理请求。这里我们放到下一篇来讲，下一篇也很重要，从原理来说也不是很难理解，就是一个过滤器链。但从 Gateway 的两大核心：路由+过滤链来说，这又很重要。
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