SpringCloudGateway开发详解

1. 路由简介：

SpringCloudGateWay 是用于替代zuul作为API网关，在gateway中有三个重要的名词：过滤器，断言，路由

过滤器与断言是路由的一部分，路由便是将请求进行一系列的处理后分发到各个服务的一个过程。

路由的过程：首先会加载断言以及路由，在接受到请求后根据断言加载的顺序会匹配到先加载的断言，只有与断言匹配了的请求才会进入路由，没有匹配到的服务会将请求当成普通的访问请求。

2：路由加载断言的方式：

断言加载的方式有四种，分别是配置文件，java编码，数据库以及注册中心

第一种配置文件：

在官方文档中主要介绍的就是配置文件的加载方式

官方地址：https://cloud.spring.io/spring-cloud-gateway/reference/html/#gateway-starter

一般的断言有三种要素：id,uri,predicate.

id是断言的标识，uri是ip+端口，predicate则是断言匹配的规则

3：示例：

新建一个springboot项目，并且引入springcloudgateway的依赖

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

在启动类注册三个全局过滤器

 @SpringBootApplication
 public class GateWayApplication {

     public static void main(String[] args) {
         SpringApplication.run(GateWayApplication.class, args);
     }

     @Bean
     @Order(-1)
     public GlobalFilter a() {
         return (exchange, chain) -> {

             return chain.filter(exchange).then(Mono.fromRunnable(() -> {
                 System.out.println(-1);
             }));
         };
     }

     @Bean
     @Order(0)
     public GlobalFilter b() {
         return (exchange, chain) -> {

             return chain.filter(exchange).then(Mono.fromRunnable(() -> {
                 System.out.println(0);
             }));
         };
     }

     @Bean
     @Order(1)
     public GlobalFilter c() {
         return (exchange, chain) -> {

             return chain.filter(exchange).then(Mono.fromRunnable(() -> {
                 System.out.println(1);
             }));
         };
     }
 }

在配置文件类配置两条路由

server.port: 7777
spring:
   application:
     name: gateway
   cloud:
     gateway:
       discovery:
         locator:
           enabled: true
           lower-case-service-id: true
       routes:
       - id: method_route
         uri: http://127.0.0.1:9999
         predicates:
         - Method=GET
       - id: method_route
         uri: http://127.0.0.1:8006
         predicates:
         - Method=GET

发送请求，请求到达后匹配的是第一条路由，由此可以知道路由匹配的顺序会根据加载的顺序来

4：SpringCloudGateWay从注册中心获得路由

在官方文档中，我们可以看到有这样的一段话

Configuring Predicates and Filters For DiscoveryClient Routes

By default the Gateway defines a single predicate and filter for routes created via a DiscoveryClient.

The default predicate is a path predicate defined with the pattern /serviceId/**, where serviceId is the id of the service from the DiscoveryClient.

The default filter is rewrite path filter with the regex /serviceId/(?<remaining>.*) and the replacement /${remaining}. This just strips the service id from the path before the request is sent downstream.

If you would like to customize the predicates and/or filters used by the DiscoveryClient routes you can do so by setting spring.cloud.gateway.discovery.locator.predicates[x] and spring.cloud.gateway.discovery.locator.filters[y]. When doing so you need to make sure to include the default predicate and filter above, if you want to retain that functionality. Below is an example of what this looks like.

地址 ：https://cloud.spring.io/spring-cloud-gateway/reference/html/#_global_filters

 spring.cloud.gateway.discovery.locator.predicates[0].name: Path
 spring.cloud.gateway.discovery.locator.predicates[0].args[pattern]: "'/'+serviceId+'/**'"
 spring.cloud.gateway.discovery.locator.predicates[1].name: Host
 spring.cloud.gateway.discovery.locator.predicates[1].args[pattern]: "'**.foo.com'"
 spring.cloud.gateway.discovery.locator.filters[0].name: Hystrix
 spring.cloud.gateway.discovery.locator.filters[0].args[name]: serviceId
 spring.cloud.gateway.discovery.locator.filters[1].name: RewritePath
 spring.cloud.gateway.discovery.locator.filters[1].args[regexp]: "'/' + serviceId + '/(?<remaining>.*)'"
 spring.cloud.gateway.discovery.locator.filters[1].args[replacement]: "'/${remaining}'"

根据文档介绍，依照这种方式，可以从注册中心获得断言与过滤器的配置

5：SpringGateWay从数据库配置路由

public class DBRouteDefinitionRepository  implements RouteDefinitionRepository

项目中实现了RouteDefinitionRepository后，springgateway会采用你实现的这个类去加载路由，如果不实现则采用他默认的方式加载路由

 public class DBRouteDefinitionRepository  implements RouteDefinitionRepository {
    //保存路由
    private final Map<String, RouteDefinition> routes = synchronizedMap(new LinkedHashMap<String, RouteDefinition>());
    
    private Logger log = LoggerFactory.getLogger(DBRouteDefinitionRepository.class);
    //初始標準
    private boolean init_flag = true;
    //
    private final GatewayProperties properties;
    private DynamicRouteServiceImpl service;
    

    public DBRouteDefinitionRepository(GatewayProperties properties) {
        this.properties = properties;
        this.service = new DynamicRouteServiceImpl();

    }
    
    @Override
    public Flux<RouteDefinition> getRouteDefinitions() {
        if(init_flag) {
            List<RouteDefinition> routeDefinitions = new ArrayList<>();
            List<RouteDefinition> rs = new ArrayList<>();
            try {
                routeDefinitions = service.quertAllRoutes();//从数据库中加载route
                rs = this.properties.getRoutes();//获得配置文件的route
                for (RouteDefinition rse : rs) {
                    routeDefinitions.add(rse);
                }
                routes.clear();
                routeDefinitions.forEach(x->routes.put(x.getId(), x));
                init_flag=false;
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
                log.error("Init Route Fail,Can't get Routes.",e);
            }
            return Flux.fromIterable(routeDefinitions);
        }else {
            return Flux.fromIterable(routes.values());
        }
        
    }

    @Override
    public Mono<Void> delete(Mono<String> routeId) {
        return routeId.flatMap(id -> {
            if (routes.containsKey(id)) {
                routes.remove(id);
                return Mono.empty();
            }
            return Mono.defer(() -> Mono.error(new NotFoundException("RouteDefinition not found: "+routeId)));
        });
    }

    @Override
    public Mono<Void> save(Mono<RouteDefinition> route) {
        return route.flatMap( r -> {
            routes.put(r.getId(), r);
            return Mono.empty();
        });
    }

}

这个是我自己实现的类，这个类可以从数据库与配置文件中获得路由配置，从数据库中获得路由配置可以根据个人的要求来

@Validated
public class RouteDefinition {

    @NotEmpty
    private String id = UUID.randomUUID().toString();

    @NotEmpty
    @Valid
    private List<PredicateDefinition> predicates = new ArrayList<>();

    @Valid
    private List<FilterDefinition> filters = new ArrayList<>();

    @NotNull
    private URI uri;

    private int order = 0;

    public RouteDefinition() {
    }

    public RouteDefinition(String text) {
        int eqIdx = text.indexOf('=');
        if (eqIdx <= 0) {
            throw new ValidationException("Unable to parse RouteDefinition text '" + text
                    + "'" + ", must be of the form name=value");
        }

        setId(text.substring(0, eqIdx));

        String[] args = tokenizeToStringArray(text.substring(eqIdx + 1), ",");

        setUri(URI.create(args[0]));

        for (int i = 1; i < args.length; i++) {
            this.predicates.add(new PredicateDefinition(args[i]));
        }
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public List<PredicateDefinition> getPredicates() {
        return predicates;
    }

    public void setPredicates(List<PredicateDefinition> predicates) {
        this.predicates = predicates;
    }

    public List<FilterDefinition> getFilters() {
        return filters;
    }

    public void setFilters(List<FilterDefinition> filters) {
        this.filters = filters;
    }

    public URI getUri() {
        return uri;
    }

    public void setUri(URI uri) {
        this.uri = uri;
    }

    public int getOrder() {
        return order;
    }

    public void setOrder(int order) {
        this.order = order;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        RouteDefinition routeDefinition = (RouteDefinition) o;
        return Objects.equals(id, routeDefinition.id)
                && Objects.equals(predicates, routeDefinition.predicates)
                && Objects.equals(order, routeDefinition.order)
                && Objects.equals(uri, routeDefinition.uri);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, predicates, uri);
    }

    @Override
    public String toString() {
        return "RouteDefinition{" + "id='" + id + '\'' + ", predicates=" + predicates
                + ", filters=" + filters + ", uri=" + uri + ", order=" + order + '}';
    }

}