spring cloud gateway 如何工作

Posted 2021-02-21

spring cloud gateway的包结构(在Idea 2019.3中展示)

这个包是spring-cloud-gateway-core.这里是真正的spring-gateway的实现的地方.
为了证明,我们打开spring-cloud-starter-gateway的pom文件

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-gateway-core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>
    </dependencies>

除了cloud-start,starter-webflux就是cloud-gateway-core.所以后面我们就分析
cloud-gateway-core这个jar包.

其中actuate中定义了GatewayControllerEndpoint,它提供了对外访问的接口.

    // TODO: Flush out routes without a definition
    @GetMapping("/routes")
    public Flux<Map<String, Object>> routes() {
        return this.routeLocator.getRoutes().map(this::serialize);
    }

    @GetMapping("/routes/{id}")
    public Mono<ResponseEntity<Map<String, Object>>> route(@PathVariable String id) {
        //......
    }
//以下方法是继承于父类,抽象类AbstractGatewayControllerEndpoint
    @PostMapping("/refresh")
    public Mono<Void> refresh() {
        this.publisher.publishEvent(new RefreshRoutesEvent(this));
        return Mono.empty();
    }

    @GetMapping("/globalfilters")
    public Mono<HashMap<String, Object>> globalfilters() {
        return getNamesToOrders(this.globalFilters);
    }

    @GetMapping("/routefilters")
    public Mono<HashMap<String, Object>> routefilers() {
        return getNamesToOrders(this.GatewayFilters);
    }

    @GetMapping("/routepredicates")
    public Mono<HashMap<String, Object>> routepredicates() {
        return getNamesToOrders(this.routePredicates);
    }
    @PostMapping("/routes/{id}")
    @SuppressWarnings("unchecked")
    public Mono<ResponseEntity<Object>> save(@PathVariable String id,
            @RequestBody RouteDefinition route) {}
    @DeleteMapping("/routes/{id}")
    public Mono<ResponseEntity<Object>> delete(@PathVariable String id) {
        return this.routeDefinitionWriter.delete(Mono.just(id))
                .then(Mono.defer(() -> Mono.just(ResponseEntity.ok().build())))
                .onErrorResume(t -> t instanceof NotFoundException,
                        t -> Mono.just(ResponseEntity.notFound().build()));
    }

    @GetMapping("/routes/{id}/combinedfilters")
    public Mono<HashMap<String, Object>> combinedfilters(@PathVariable String id) {
        // TODO: missing global filters
    }

config包里定义了一些Autoconfiguration和一些properties.读取配置文件就在这里完成.

我们这里看一下GatewayProperties.java

@ConfigurationProperties("spring.cloud.gateway")
@Validated
public class GatewayProperties {

    /**
     * List of Routes.
     */
    @NotNull
    @Valid
    private List<RouteDefinition> routes = new ArrayList<>();

    /**
     * List of filter definitions that are applied to every route.
     */
    private List<FilterDefinition> defaultFilters = new ArrayList<>();

    private List<MediaType> streamingMediaTypes = Arrays
            .asList(MediaType.TEXT_EVENT_STREAM, MediaType.APPLICATION_STREAM_JSON);
    #该类包括三个属性,路由列表,默认过滤器列表和MediaType列表.路由列表中的路由定义RouteDefinition.
        过滤器中定义的FilterDefinition.

discovery定义了注册中心的一些操作.
event定义了一系列事件,都继承自ApplicationEvent.
filter定义了spring gateway实现的一些过滤器,包括gatewayfilter,globalfilter.