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目前SpringCloud Gateway只支持配置文件yml、properties和配置文件@Configuration的方式配置路由。这种方式有弊端，就是如果需要变更路由信息，修改路由规则，然后重启Gateway，修改或增加的路由规则才会生效。如果出现该问题，在Gateway重启的这段时间里，所有接入Gateway服务的应用都不可用。这肯定是不可行的。

Gateway默认的配置

yml配置文件

@Configuration

路由初始化

不管是什么方式配置路由，这些配置最后都会被封装到RouteDefinition中

public class RouteDefinition {
    private String id;
    @NotEmpty
    @Valid
    private List<PredicateDefinition> predicates = new ArrayList<>();
    @Valid
    private List<FilterDefinition> filters = new ArrayList<>();
    @NotNull
    private URI uri;
    private Map<String, Object> metadata = new HashMap<>();
    private int order = 0;
    public RouteDefinition() {
    }
    ...
}

一个路由配置就是一个RouteDefinition对象，一个RouteDefinition对应一个ID，如果不设置，默认为uuid，所有路由信息在系统启动的时候被加载进内存里

如图框住的部分就是加载yml文件，它返回PropertiesRouteDefinitionLocator对象，该对象实现RouteDefinitionLocator接口，该接口是路由的装载器

public interface RouteDefinitionLocator {

    Flux<RouteDefinition> getRouteDefinitions();

}

该接口只有一个方法，就是获取路由配置，该接口有多个实现类，分别对应不同的配置路由的方式

CachingRouteDefinitionLocator -RouteDefinitionLocator包装类，缓存目标RouteDefinitionLocator 为routeDefinitions提供缓存功能
CompositeRouteDefinitionLocator -RouteDefinitionLocator包装类，组合多种 RouteDefinitionLocator 的实现，为 routeDefinitions提供统一入口
PropertiesRouteDefinitionLocator-从配置文件(GatewayProperties 例如，YML / Properties 等 ) 读取RouteDefinition
DiscoveryClientRouteDefinitionLocator-从注册中心( 例如，Eureka / Consul / Zookeeper / Etcd 等 )读取RouteDefinition
RouteDefinitionRepository-从存储器( 例如，内存 / Redis / MySQL 等 )读取RouteDefinition

初始化顺序是

配置文件加载初始化 PropertiesRouteDefinitionLocator-->CompositeRouteDefinitionLocator
存储器中加载初始化RouteDefinitionRepository-->CompositeRouteDefinitionLocator
注册中心加载初始化DiscoveryClientRouteDefinitionLocator-->CompositeRouteDefinitionLocator

而使用存储器中初始化的条件是，没有定义RouteDefinitionRepository

@Bean
@ConditionalOnMissingBean(RouteDefinitionRepository.class)
public InMemoryRouteDefinitionRepository inMemoryRouteDefinitionRepository() {
    return new InMemoryRouteDefinitionRepository();
}

路由配置从数据库中获取

因此，我们可以通过实现RouteDefinitionRepository接口来自定义路由配置的获取方式

实现RouteDefinitionRepository接口

@Component
public class DBARouteDefinitionRepository implements RouteDefinitionRepository {

    @Resource
    private GatewayDao gatewayDao;

    @Override
    public Flux<RouteDefinition> getRouteDefinitions() {
        List<RouteDefinition> gatewayRouteEntityList = getRouteConfig();
        return Flux.fromIterable(gatewayRouteEntityList);
    }

    private List<RouteDefinition> getRouteConfig() {
        List<RoutesEntity> routesEntities = gatewayDao.queryAllRoutes();

        List<RouteDefinition> definitions = new ArrayList<>();

        //组装RouteDefinition
        for (RoutesEntity entity : routesEntities) {
            RouteDefinition definition = new RouteDefinition();

            Map<String,String> predicateParams = new HashMap<>();
            PredicateDefinition predicate = new PredicateDefinition();

            Map<String,String> filterParams = new HashMap<>();
            FilterDefinition filter = new FilterDefinition();

            URI uri = UriComponentsBuilder.fromHttpUrl(entity.getUri()).build().toUri();

            predicate.setName("Path");
            predicateParams.put("pattern",entity.getPredicates());
            predicate.setArgs(predicateParams);

            //过滤暂时不写
            //filter.setName("StripPrefix");
            //TODO 动态过滤

            definition.setPredicates(Arrays.asList(predicate));
            //definition.setFilters();

            definition.setUri(uri);
            definition.setId(entity.getRouteId());

            definitions.add(definition);
        }

        return definitions;
    }

    @Override
    public Mono<Void> save(Mono<RouteDefinition> route) {
        return null;
    }

    @Override
    public Mono<Void> delete(Mono<String> routeId) {
        return null;
    }
}

动态路由

@Service
public class DBARouteConfigService implements ApplicationEventPublisherAware {

    @Resource
    private GatewayDao gatewayDao;

    private ApplicationEventPublisher applicationEventPublisher;


    public int add(RoutesEntity entity){
        gatewayDao.create(entity);
        applicationEventPublisher.publishEvent(new RefreshRoutesEvent(this));
        return 1;
    }

    public int delete(String routeId) {
        gatewayDao.deleteByRouteId(routeId);
        applicationEventPublisher.publishEvent(new RefreshRoutesEvent(this));
        return 1;
    }

    public int update(RoutesEntity entity) {
        gatewayDao.updateRouteById(entity);
        applicationEventPublisher.publishEvent(new RefreshRoutesEvent(this));
        return 1;
    }

    /**
     * 发布事件
     * @param applicationEventPublisher
     */
    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.applicationEventPublisher = applicationEventPublisher;
    }
}

在数据库中修改删除路由配置，然后再执行一下RefreshRoutesEvent事件，即可刷新路由配置，无需重启，立刻生效