本文基于 spring cloud gateway 2.0.1
1、简介
直接 获取 路 由 的 方法 是 通过 RouteLocator 接口 获取。 同样， 该 顶 级 接口 有多 个 实现 类，
RouteLocator 路由定位器，顾名思义就是用来获取路由的方法。该路由定位器为顶级接口有多个实现类，如类图所示，本节会对其实现类一一进行介绍。
通过类图可知，路由定位器接口有三种实现方法：
RouteDefinitionRouteLocator 基于路由定义的定位器
CachingRouteLocator 基于缓存的路由定位器
CompositeRouteLocator 基于组合方式的路由定位器
2、RouteLocator 路由定位器
与上节学习的路由定义定位器接口类似，RouteLocator 路由定位器只有一个 getRoutes 方法，用来获取路由信息。
public interface RouteLocator {
//获取路由对象
Flux<Route> getRoutes();
}
2.1、Route 路由对象
Route 路由定义了路由断言、过滤器、路由地址及路由优先级等信息。当请求到达时，在转发到代理服务之前，会依次经过路由断言匹配路由 和 网关过滤器处理。
public class Route implements Ordered {
//路由 Id
private final String id;
//路由地址
private final URI uri;
//路由的优先级
private final int order;
//路由断言，判断请求路径是否匹配
private final AsyncPredicate<ServerWebExchange> predicate;
//网关过滤器
private final List<GatewayFilter> gatewayFilters;
-----------------------省略-------------------------
}
3、 RouteDefinitionRouteLocator 基于路由定义的定位器
3.1、初始化
RouteDefinitionRouteLocator 构造函数有多个参数：路由定义定位器、路由断言工厂、网关过滤器及网关配置对象。 根据传入的参数，设置 routeDefinitionLocator 和 网关配置，并初始化路由断言 和 网关过滤器。 RouteDefinitionRouteLocator 的实现方式是基于路由定义来获取路由，它实现了 RouteLocator 接口，用来获取路由信息。
public class RouteDefinitionRouteLocator implements RouteLocator, BeanFactoryAware, ApplicationEventPublisherAware {
protected final Log logger = LogFactory.getLog(getClass());
private final RouteDefinitionLocator routeDefinitionLocator;
private final Map<String, RoutePredicateFactory> predicates = new LinkedHashMap<>();
private final Map<String, GatewayFilterFactory> gatewayFilterFactories = new HashMap<>();
private final GatewayProperties gatewayProperties;
private final SpelExpressionParser parser = new SpelExpressionParser();
private BeanFactory beanFactory;
private ApplicationEventPublisher publisher;
public RouteDefinitionRouteLocator(RouteDefinitionLocator routeDefinitionLocator,
List<RoutePredicateFactory> predicates,
List<GatewayFilterFactory> gatewayFilterFactories,
GatewayProperties gatewayProperties) {
//设置路由定义定位器
this.routeDefinitionLocator = routeDefinitionLocator;
//初始化路由断言工厂
initFactories(predicates);
//初始化网关过滤器
gatewayFilterFactories.forEach(factory -> this.gatewayFilterFactories.put(factory.name(), factory));
this.gatewayProperties = gatewayProperties;
}
@Autowired
private Validator validator;
@Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
this.beanFactory = beanFactory;
}
@Override
public void setApplicationEventPublisher(ApplicationEventPublisher publisher) {
this.publisher = publisher;
}
private void initFactories(List<RoutePredicateFactory> predicates) {
predicates.forEach(factory -> {
String key = factory.name();
if (this.predicates.containsKey(key)) {
this.logger.warn("A RoutePredicateFactory named "+ key
+ " already exists, class: " + this.predicates.get(key)
+ ". It will be overwritten.");
}
this.predicates.put(key, factory);
if (logger.isInfoEnabled()) {
logger.info("Loaded RoutePredicateFactory [" + key + "]");
}
});
}
--------------------------------省略---------------------------------
}
此种方式的路由获取是通过 RouteDefinitionRouteLocator 获取 RouteDefinition 并将路由定义转换成路由对象
这里的routeDefinitionLocator是CompositeRouteDefinitionLocator，它组合了InMemoryRouteDefinitionRepository、PropertiesRouteDefinitionLocator、DiscoveryClientRouteDefinitionLocator三个RouteDefinitionLocator。
PropertiesRouteDefinitionLocator是直接使用GatewayProperties的getRoutes()获取，其是通过spring.cloud.gateway.routes配置得来。
3.2、RouteDefinition 转换成 Route 的流程
 {
return this.routeDefinitionLocator.getRouteDefinitions()
.map(this::convertToRoute)
//TODO: error handling
.map(route -> {
if (logger.isDebugEnabled()) {
logger.debug("RouteDefinition matched: " + route.getId());
}
return route;
});
/* TODO: trace logging
if (logger.isTraceEnabled()) {
logger.trace("RouteDefinition did not match: " + routeDefinition.getId());
}*/
}
private Route convertToRoute(RouteDefinition routeDefinition) {
AsyncPredicate<ServerWebExchange> predicate = combinePredicates(routeDefinition);
List<GatewayFilter> gatewayFilters = getFilters(routeDefinition);
return Route.async(routeDefinition)
.asyncPredicate(predicate)
.replaceFilters(gatewayFilters)
.build();
}
getRoutes() ：根据传入的 RouteDefinitionLocator 获取路由定义对象，使用map方法将每个 RouteDefinition 转换为 Route。
RouteDefinitionLocator#convertToRoute ：是具体的转换方法，转换过程中涉及到路由断言 和 网关过滤器的处理，最后构建为Route 对象。
此处网关过滤器处理包括两种，一种是默认过滤器，作用于所有路由；一种是指定路由的自定义过滤器。首先获取默认过滤器，根据过滤器名称获取对应的过滤器，最终转换成有优先级的OrderedGatewayFilter。
3.2.1、convertToRoute##combinePredicates
combinePredicates主要是对找出来的predicate进行and操作
private AsyncPredicate<ServerWebExchange> combinePredicates(RouteDefinition routeDefinition) {
List<PredicateDefinition> predicates = routeDefinition.getPredicates();
AsyncPredicate<ServerWebExchange> predicate = lookup(routeDefinition, predicates.get(0));
for (PredicateDefinition andPredicate : predicates.subList(1, predicates.size())) {
AsyncPredicate<ServerWebExchange> found = lookup(routeDefinition, andPredicate);
predicate = predicate.and(found);
}
return predicate;
}
@SuppressWarnings("unchecked")
private AsyncPredicate<ServerWebExchange> lookup(RouteDefinition route, PredicateDefinition predicate) {
RoutePredicateFactory<Object> factory = this.predicates.get(predicate.getName());
if (factory == null) {
throw new IllegalArgumentException("Unable to find RoutePredicateFactory with name " + predicate.getName());
}
Map<String, String> args = predicate.getArgs();
if (logger.isDebugEnabled()) {
logger.debug("RouteDefinition " + route.getId() + " applying "
+ args + " to " + predicate.getName());
}
Map<String, Object> properties = factory.shortcutType().normalize(args, factory, this.parser, this.beanFactory);
Object config = factory.newConfig();
ConfigurationUtils.bind(config, properties,
factory.shortcutFieldPrefix(), predicate.getName(), validator);
if (this.publisher != null) {
this.publisher.publishEvent(new PredicateArgsEvent(this, route.getId(), properties));
}
return factory.applyAsync(config);
}
3.2.2、convertToRoute##getFilters
getFilters 主要是利用loadGatewayFilters获取filter，使用AnnotationAwareOrderComparator进行排序
loadGatewayFilters利用工厂方法，使用GatewayFilterFactory根据config 获取具体的GatewayFilter实例
@SuppressWarnings("unchecked")
private List<GatewayFilter> loadGatewayFilters(String id, List<FilterDefinition> filterDefinitions) {
List<GatewayFilter> filters = filterDefinitions.stream()
.map(definition -> {
GatewayFilterFactory factory = this.gatewayFilterFactories.get(definition.getName());
if (factory == null) {
throw new IllegalArgumentException("Unable to find GatewayFilterFactory with name " + definition.getName());
}
Map<String, String> args = definition.getArgs();
if (logger.isDebugEnabled()) {
logger.debug("RouteDefinition " + id + " applying filter " + args + " to " + definition.getName());
}
Map<String, Object> properties = factory.shortcutType().normalize(args, factory, this.parser, this.beanFactory);
Object configuration = factory.newConfig();
ConfigurationUtils.bind(configuration, properties,
factory.shortcutFieldPrefix(), definition.getName(), validator);
GatewayFilter gatewayFilter = factory.apply(configuration);
if (this.publisher != null) {
this.publisher.publishEvent(new FilterArgsEvent(this, id, properties));
}
return gatewayFilter;
})
.collect(Collectors.toList());
ArrayList<GatewayFilter> ordered = new ArrayList<>(filters.size());
for (int i = 0; i < filters.size(); i++) {
GatewayFilter gatewayFilter = filters.get(i);
if (gatewayFilter instanceof Ordered) {
ordered.add(gatewayFilter);
}
else {
ordered.add(new OrderedGatewayFilter(gatewayFilter, i + 1));
}
}
return ordered;
}
private List<GatewayFilter> getFilters(RouteDefinition routeDefinition) {
List<GatewayFilter> filters = new ArrayList<>();
//TODO: support option to apply defaults after route specific filters?
if (!this.gatewayProperties.getDefaultFilters().isEmpty()) {
filters.addAll(loadGatewayFilters("defaultFilters",
this.gatewayProperties.getDefaultFilters()));
}
if (!routeDefinition.getFilters().isEmpty()) {
filters.addAll(loadGatewayFilters(routeDefinition.getId(), routeDefinition.getFilters()));
}
AnnotationAwareOrderComparator.sort(filters);
return filters;
}
4、 CachingRouteLocator 基于缓存的路由定位器
public class CachingRouteLocator implements RouteLocator {
private final RouteLocator delegate;
private final Flux<Route> routes;
private final Map<String, List> cache = new HashMap<>();
public CachingRouteLocator(RouteLocator delegate) {
this.delegate = delegate;
routes = CacheFlux.lookup(cache, "routes", Route.class)
.onCacheMissResume(() -> this.delegate.getRoutes().sort(AnnotationAwareOrderComparator.INSTANCE));
}
@Override
public Flux<Route> getRoutes() {
return this.routes;
}
/**
* Clears the routes cache
* @return routes flux
*/
public Flux<Route> refresh() {
this.cache.clear();
return this.routes;
}
@EventListener(RefreshRoutesEvent.class)
/* for testing */ void handleRefresh() {
refresh();
}
}
基于缓存的路由定位器比较简单和缓存路由定义定位器比较类似，只需要调用 RouteLocator# getRoutes 即可获取路由。
根据传入的路由定位器获取路由信息并存储到缓存中。通过监听 RefreshRoutesEvent 事件刷新缓存的路由信息。
5、 CompositeRouteLocator 基于组合方式的路由定位器
public class CompositeRouteLocator implements RouteLocator {
private final Flux<RouteLocator> delegates;
public CompositeRouteLocator(Flux<RouteLocator> delegates) {
this.delegates = delegates;
}
@Override
public Flux<Route> getRoutes() {
return this.delegates.flatMap(RouteLocator::getRoutes);
}
}
组合方式的路由定位器，将实现 RouteLocator 接口的路由定位器组合在一起，提供获取路由的统一入口。
6、小结
RouteLocator 接口用于获取路由信息，其有三个实现类
RouteDefinitionRouteLocator
CompositeRouteLocator
CachingRouteLocator
最终使用的是CachingRouteLocator，它包装了CompositeRouteLocator，而CompositeRouteLocator则组合了RouteDefinitionRouteLocator。
RouteDefinitionRouteLocator 与 RouteDefinitionLocator比较容易混淆，前者是一个RouteLocator（路由定位器），后者是一个RouteDefinitionLocator（路由定义定位器），前者的 RouteDefinitionRouteLocator 主要从后者获取路由定义信息。
