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I. Overview

In the request processing process of Spring-Cloud-Gateway, the final gateway sends the request to the filter linked list for processing.

Core interface: GatewayFilter,GlobalFilter,GatewayFilterChain.

View the overall class diagram

Second, the function of gateway filter

When building an entire API service using microservices, there are generally many different applications running, such as mst-user-service, mst-good-service, and mst-order-service shown in the figure above, all of which require Authentication of client requests. The simplest and roughest way is to implement a set of filters or interceptors for verification for each microservice application, as shown above.

These non-business verifications are completed through the front-end gateway services.

III. The life cycle of Filter

Spring Cloud Gateway's Filter has two life cycles: "pre" and "post".

"pre" and "post" are called before and after the request is executed, respectively, similar to the relevant life cycle in Zuul Filter or Spring Interceptor, but somewhat different in form.

Zuul's Filter is specified by the filterType () method, and a Filter can only correspond to one type, either "pre" or "post". Spring Interceptor is implemented by rewriting three methods in HandlerInterceptor. While Spring Cloud Gateway is based on Project Reactor and WebFlux and uses responsive programming style, open its Filter interface GatewayFilter and you will find that it has only one method, filter.

Fourth, core interface interpretation 4.1, GatewayFilterChain-- gateway filter linked list

/ * * Gateway filter list API * chain call for filter * / public interface GatewayFilterChain {/ * list start call entry method * / Mono filter (ServerWebExchange exchange);}

Default implementation

/ * * Gateway filter linked list, which is used for the linked call of the filter * the default implementation of the filter chain table API, * contains two construction functions: * 1. The collection parameter construction is used to initialize the build linked list * 2. The index,parent parameter is used to build the next linked list corresponding to the current filter execution * / private static class DefaultGatewayFilterChain implements GatewayFilterChain {/ * the current filter is indexed in the collection * / private final int index / * * filter collection * / private final List filters; public DefaultGatewayFilterChain (List filters) {this.filters = filters; this.index = 0 } / * build * @ param parent the FilterChain * @ param index corresponding to the last execution filter * / private DefaultGatewayFilterChain (DefaultGatewayFilterChain parent, int index) {this.filters = parent.getFilters (); this.index = index } public List getFilters () {return filters;} / * @ param exchange the current server exchange * @ return * / @ Override public Mono filter (ServerWebExchange exchange) {return Mono.defer (()-> {if (this.index)

< filters.size()) { //获取当前索引的过滤器 GatewayFilter filter = filters.get(this.index); //构建当前索引的下一个过滤器的FilterChain DefaultGatewayFilterChain chain = new DefaultGatewayFilterChain(this, this.index + 1); //调用过滤器的filter方法执行过滤器 return filter.filter(exchange, chain); } else { //当前索引大于等于过滤集合大小，标识所有链表都已执行完毕，返回空 return Mono.empty(); // complete } }); } } 过滤器的GatewayFilterChain 执行顺序 通过GatewayFilter集合构建顶层的GatewayFilterChain 调用顶层GatewayFilterChain，获取第一个Filter，并创建下一个Filter索引对应的GatewayFilterChain 调用filter的filter方法执行当前filter，并将下次要执行的filter对应GatewayFilterChain传入。 4.2、GatewayFilter--网关路由过滤器 /** * 网关路由过滤器， * Contract for interception-style, chained processing of Web requests that may * be used to implement cross-cutting, application-agnostic requirements such * as security, timeouts, and others. Specific to a Gateway * */public interface GatewayFilter extends ShortcutConfigurable { String NAME_KEY = "name"; String VALUE_KEY = "value"; /** * 过滤器执行方法 * Process the Web request and (optionally) delegate to the next * {@code WebFilter} through the given {@link GatewayFilterChain}. * @param exchange the current server exchange * @param chain provides a way to delegate to the next filter * @return {@code Mono} to indicate when request processing is complete */ Mono filter(ServerWebExchange exchange, GatewayFilterChain chain);} 网关过滤器接口，有且只有一个方法filter，执行当前过滤器，并在此方法中决定过滤器链表是否继续往下执行。 1️⃣、OrderedGatewayFilter--排序 /** * 排序的网关路由过滤器，用于包装真实的网关过滤器，已达到过滤器可排序 */public class OrderedGatewayFilter implements GatewayFilter, Ordered { //目标过滤器 private final GatewayFilter delegate; //排序字段 private final int order; public OrderedGatewayFilter(GatewayFilter delegate, int order) { this.delegate = delegate; this.order = order; } @Override public Mono filter(ServerWebExchange exchange, GatewayFilterChain chain) { return this.delegate.filter(exchange, chain); }} OrderedGatewayFilter实现类主要目的是为了将目标过滤器包装成可排序的对象类型。是目标过滤器的包装类 2️⃣、GatewayFilterAdapter 　　/** * 全局过滤器的包装类，将全局路由包装成统一的网关过滤器 */ private static class GatewayFilterAdapter implements GatewayFilter { /** * 全局过滤器 */ private final GlobalFilter delegate; public GatewayFilterAdapter(GlobalFilter delegate) { this.delegate = delegate; } @Override public Mono filter(ServerWebExchange exchange, GatewayFilterChain chain) { return this.delegate.filter(exchange, chain); } } GatewayFilterAdapter实现类主要目的是为了将GlobalFilter过滤器包装成GatewayFilter类型的对应。是GlobalFilter过滤器的包装类 4.3、GlobalFilter 　　 　　GlobalFilter 为请求业务以及路由的URI转换为真实业务服务的请求地址的核心过滤器，不需要配置，模式系统初始化时加载，并作用在每个路由上。 1️⃣、初始化加载，通过GatewayAutoConfiguration自动创建 //GatewayAutoConfiguration 类 /** * 全局过滤器，用户通过HttpClient转发请求 */ @Bean public NettyRoutingFilter routingFilter(HttpClient httpClient, ObjectProvider headersFilters) { return new NettyRoutingFilter(httpClient, headersFilters); } /** * 全局的过滤器，用户将HttpClient客户端转发请求的响应写入到原始的请求响应中 */ @Bean public NettyWriteResponseFilter nettyWriteResponseFilter(GatewayProperties properties) { return new NettyWriteResponseFilter(properties.getStreamingMediaTypes()); } //GatewayLoadBalancerClientAutoConfiguration 类 /** * 全局过滤器，用于在通过负载均衡客户端选择服务实例信息 */ @Bean @ConditionalOnBean(LoadBalancerClient.class) public LoadBalancerClientFilter loadBalancerClientFilter(LoadBalancerClient client) { return new LoadBalancerClientFilter(client); } 2️⃣、GlobalFilter转换成GatewayFilter，并作用于每个路由上，在FilteringWebHandler实现 //FilteringWebHandler类 /** * 包装加载全局的过滤器，将全局过滤器包装成GatewayFilter */ private static List loadFilters(List filters) { return filters.stream() .map(filter ->

{/ / package all global filters as gateway filter GatewayFilterAdapter gatewayFilter = new GatewayFilterAdapter (filter); / / determine whether the global filter implements the sortable interface if (filter instanceof Ordered) {int order = ((Ordered) filter) .getOrder () / / packaged as a sortable gateway filter return new OrderedGatewayFilter (gatewayFilter, order);} return gatewayFilter;}) .filters (Collectors.toList ()) } @ Override public Mono handle (ServerWebExchange exchange) {/ / get the route instance of the request context setting Route route = exchange.getRequiredAttribute (GATEWAY_ROUTE_ATTR); / / get the gateway filter collection List gatewayFilters = route.getFilters () under the route definition; / / combine the global filter and route configuration filter List combined = new ArrayList (this.globalFilters) / / add a route configuration filter to the tail of the collection combined.addAll (gatewayFilters); / / sort the filter / / TODO: needed or cached? AnnotationAwareOrderComparator.sort (combined); logger.debug ("Sorted gatewayFilterFactories:" + combined); / / create a filter linked list to call return new DefaultGatewayFilterChain (combined) .filter (exchange);}

The loadFilters method is to wrap the global route as a GatewayFilter using GatewayFilterAdapter

Handle method

Gets the route Route used by the current request

Get the filter collection route.getFilters () for the route configuration

Merge full filter with routing configuration filter combined

Sort filter AnnotationAwareOrderComparator.sort

The top-level linked list DefaultGatewayFilterChain is built through the filter collection and the filter method of the linked list is called on its current request.

Summary

There are two filter interfaces for Spring-Cloud-Gateway:

GlobalFilter: global filter, which does not need to be configured in the configuration file, acts on all routes, and is eventually packaged into a filter recognized by GatewayFilterChain through GatewayFilterAdapter

GatewayFilter: need to be configured under specific routes through spring.cloud.routes.filters, only on the current route or globally via spring.cloud.default-filters, and on all routes

5. GatewayFilterFactory configure route filter

Route filters allow incoming HTTP requests or outgoing HTTP responses to be modified in some way. The scope of the path filter is limited to a specific path.

1 ️load, load GatewayFilter

In the route locator and see the translation routing method by route definition, which contains the section that translates the filter (GatewayFilter) by filter definition (FilterDefinition), the source code in the RouteDefinitionRouteLocator class is as follows:

/ * load filter, load * / @ SuppressWarnings ("unchecked") private List loadGatewayFilters (String id, List filterDefinitions) {/ / traverse filter definition according to filter definition Convert the filter definition to the corresponding filter List filters = filterDefinitions.stream () .map (definition-> {/ / get filter creation factory GatewayFilterFactory factory = this.gatewayFilterFactories.get (definition.getName ()) by filter definition name) If (factory = = null) {throw new IllegalArgumentException ("Unable to find GatewayFilterFactory with name" > getFilters method merges the global filter in the configuration with the filter configured by the route itself, and sorts them (global configuration filter information is obtained through gatewayProperties.getDefaultFilters ()) loadGatewayFilters traverses the FilterDefinition defined by the route and converts it into a GatewayFilter object through the corresponding GatewayFilterFactory. 2 ️filters, GatewayFilterFactory configuration filter creation factory create GatewayFilter object default built-in many GatewayFilterFactory implementation classes, used to create gateway filters with different functions. Class diagram subclasses and their partitions 3 ️blocks, AddResponseHeaderGatewayFilterFactory creation parsing / * * response header adding data filter * users add configuration data in response header * / public class AddResponseHeaderGatewayFilterFactory extends AbstractNameValueGatewayFilterFactory {@ Override public GatewayFilter apply (NameValueConfig config) {return (exchange) Chain)-> {/ / get Response and add configuration data to header exchange.getResponse () .getHeaders () .add (config.getName (), config.getValue ()) Return chain.filter (exchange);}. Configuration example: spring: cloud: gateway: default-filters:-AddResponseHeader=X-Response-Default-Foo, Default-Bar AddResponseHeader=X-Response-Default-Foo, Default-Bar will be parsed into a FilterDefinition object (name= AddResponseHeader, args= [XmurResponseWright DefaultFaut Name]) through FilterDefinition's Name to find AddResponseHeaderGatewayFilterFactory factory to create Config object (name=X-Response-Default-Foo,value=Default-Bar) through FilterDefinition's args to create GatewayFilter object through AddResponseHeaderGatewayFilterFactory factory's apply method. 4 ️header, full configuration 5.1, request header spring: cloud: gateway: routes:-id: add_request_header_route uri: http://example.org filters:-AddRequestHeader=X-Request-Foo, Bar name and value, which will add X-Request-Foo:Bar headers to all downstream request headers that match the request. Remove the request header filters:-RemoveRequestHeader=X-Request-Foo 5.2, the request parameter filters:-AddRequestParameter=foo, bar, which adds foo = bar to the query string of all matching requests for downstream requests. Add the response header filters:-AddResponseHeader=X-Response-Foo, Bar, which adds the X-Response-Foo:Bar header to the downstream response header of all matching requests. Remove the response header filters:-RemoveResponseHeader=X-Response-Foo set the response header filters:-SetResponseHeader=X-Response-Foo, Bar this GatewayFilter will replace all headers with the given name instead of adding it. The path prefix filters:-PrefixPath=/mypath this will make the / mypath prefix to all matching requested paths. So the request for / hello is sent to / mypath / hello. The original host header has no parameters, and this filter sets the request properties that the route filter will check to determine whether the original host header should be sent instead of the one determined by the http client. Filters:-PreserveHostHeader 5.6Redirect filters:-RedirectTo=302, http://acme.org this will send the status 302 with the Location:http://acme.org header to perform the redirection. Rewrite the path predicates:-Path=/foo/** filters:-RewritePath=/foo/ (?. *), / $\ {segment} the request path for / foo/ bar, which will set the path to / bar before issuing the downstream request. Note that due to the YAML specification, $\ is replaced with $. Save Sessionpredicates:-Path=/foo/** filters:-SaveSession 5.9.The path template SetPath GatewayFilter Factory uses path template parameters. It provides a simple way to manipulate the request path by allowing templated path segments. Predicates:-Path=/foo/ {segment} filters:-SetPath=/ {segment} request path for / foo/ bar, which sets the path to / bar before issuing downstream requests. 5.10. Set the response status spring: cloud: gateway: routes:-id: setstatusstring_route uri: http://example.org filters:-SetStatus=BAD_REQUEST-id: setstatusint_route uri: http://example.org filters:-SetStatus=401 5.11. The request parameter split parts parameter indicates the number of parts in the path to be split from the request before sending the request downstream. Predicates:-Path=/name/** filters:-StripPrefix=2 when a request is made to / name/ bar / foo through the gateway, the request for nameservice will be similar to http:// nameservice / foo. 5.12. Retry retries: retry: number of retries statuses: status: HTTP status code that should be retried, use org.springframework.http.HttpStatus to represent methods: method: HTTP method that should be retried, use org.springframework.http.HttpMethod to represent series: series: status code series to retry Use org.springframework.http.HttpStatus.Series to express routes:-id: retry_test uri: http://localhost:8080/flakey predicates:-Host=*.retry.com filters:-name: Retry args: retries: 3 statuses: BAD_GATEWAY 5.13, Hystrix GatewayFilter Factory https://cloud.spring.io/spring-cloud-static/Finchley.SR1/single/spring-cloud.html#_hystrix_gatewayfilter_factory5.14, request speed limit RequestRateLimiter GatewayFilter Factory5.15, security header SecureHeaders GatewayFilter Factory thank you for reading The above is the content of "the use of spring cloud gateway- filter". 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