springGateway常见类分析
本文将springGateway的重要类提出来，从宏观角度理解下这个框架。
1.HttpHandler
底层reactor将netty解析好的request封装成request，response交给此类处理。这是最原始的处理请求的接口，最接近底层netty的。
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public interface HttpHandler {
Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response);
}
2.WebHandler
HttpHandler的另一个抽象，参数exchange包装了request + response。此类类比于j2ee里面的servlet。
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public interface WebHandler {
Mono<Void> handle(ServerWebExchange exchange);
}
3.WebFilter
配合WebHandler使用，提供拦截器功能，此类类比于j2ee里面的filter
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public interface WebFilter {
Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain);
}
4.WebHandlerDecorator
WebHandler的代理类，全部委托给代理类执行。仍然实现WebHandler接口。
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public class WebHandlerDecorator implements WebHandler {
private final WebHandler delegate;
public WebHandlerDecorator(WebHandler delegate) {
this.delegate = delegate;
}
@Override
public Mono<Void> handle(ServerWebExchange exchange) {
return this.delegate.handle(exchange);
}
}
5.FilteringWebHandler
将WebFilter和WebHandler组合在一起，变成一个WebHandler，执行此WebHandler之前会先经过WebFilter链。
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public class FilteringWebHandler extends WebHandlerDecorator {
private final DefaultWebFilterChain chain;
public FilteringWebHandler(WebHandler handler, List<WebFilter> filters) {
super(handler);
this.chain = new DefaultWebFilterChain(handler, filters);
}
@Override
public Mono<Void> handle(ServerWebExchange exchange) {
return this.chain.filter(exchange);
}
}
6.WebExceptionHandler
异常处理，可以配置多个异常处理，如果已经处理完成则返回Mono
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public interface WebExceptionHandler {
Mono<Void> handle(ServerWebExchange exchange, Throwable ex);
}
7.ExceptionHandlingWebHandler
仍然是WebHandler的代理类，使用try catch包住执行逻辑，抛异常时使用exceptionHandlers处理异常。
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public class ExceptionHandlingWebHandler extends WebHandlerDecorator {
private final List<WebExceptionHandler> exceptionHandlers;
@Override
public Mono<Void> handle(ServerWebExchange exchange) {
Mono<Void> completion;
try {
completion = super.handle(exchange);
}
catch (Throwable ex) {
completion = Mono.error(ex);
}
for (WebExceptionHandler handler : this.exceptionHandlers) {
completion = completion.onErrorResume(ex -> handler.handle(exchange, ex));
}
return completion;
}
}
8.HttpWebHandlerAdapter
同时实现了WebHandler 和 HttpHandler接口，提供适配转换功能，将WebHandler适配成HttpHandler供底层调用，因为netty底层需要的是HttpHandler实现类，我们框架是以WebHandler作为基础开发的。
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public class HttpWebHandlerAdapter extends WebHandlerDecorator implements HttpHandler {
@Override
public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response) {
ServerWebExchange exchange = createExchange(request, response);
return getDelegate().handle(exchange)
.doOnSuccess(aVoid -> logResponse(exchange))
.onErrorResume(ex -> handleUnresolvedError(exchange, ex))
.then(Mono.defer(response::setComplete));
}
}
9.DispatcherHandler
实现了WebHandler接口，类似于springMvc的DispatcherServlet一样，先是通过handlerMapping查找mapping，在通过handlerAdapter执行mapping，再通过HandlerResultHandler处理返回结果。
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public class DispatcherHandler implements WebHandler, ApplicationContextAware {
@Override
public Mono<Void> handle(ServerWebExchange exchange) {
return Flux.fromIterable(this.handlerMappings)
.concatMap(mapping -> mapping.getHandler(exchange))
.next()
.switchIfEmpty(createNotFoundError())
.flatMap(handler -> invokeHandler(exchange, handler))
.flatMap(result -> handleResult(exchange, result));
}
}
10.GlobalFilter
这是gateway独有的filter，签名和WebFilter一样，内置十个GloblFilter用来做路由功能。
一般不需要创建GlobalFilter。
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public interface GlobalFilter {
Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain);
}
11.GatewayFilter
也是gateway独有的，签名和GlobalFilter一样，为了区分是系统默认的还是用户自定义了，我们写gateway的filter通常实现此接口。
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public interface GatewayFilter extends ShortcutConfigurable {
Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain);
}
10.Route
gateway独有的类，系类相当于数据类，只是用来将路由相关的类，整理在一起。
-
uri 标识目标地址
-
predicate 判断请求是否符合此route
-
gatewayFilters 存储的filter。
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public class Route implements Ordered {
private final String id;
private final URI uri;
private final int order;
private final AsyncPredicate<ServerWebExchange> predicate;
private final List<GatewayFilter> gatewayFilters;
11. RouteLocator
gateway独有的类，使用Flux封装多个Route，提供Route的存储功能。
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public interface RouteLocator {
Flux<Route> getRoutes();
}
12.FilteringWebHandler
gateway独有的类，和上面webFlux也有这个类，只是重名了而已。
此类实现了WebHandler接口，但实际执行逻辑是多个GatewayFIlter组成的FIlter链。
构造方法里传入globalFilters，handler方法里，从route上获取GatewayFilter，将用户Filter和全局FIlter合并成FilterChain，再执行。
此类可以看成在tomcat环境下，只有filter链，没有servlet。
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public class FilteringWebHandler implements WebHandler {
protected static final Log logger = LogFactory.getLog(FilteringWebHandler.class);
private final List<GatewayFilter> globalFilters;
public FilteringWebHandler(List<GlobalFilter> globalFilters) {
this.globalFilters = loadFilters(globalFilters);
}
@Override
public Mono<Void> handle(ServerWebExchange exchange) {
Route route = exchange.getRequiredAttribute(GATEWAY_ROUTE_ATTR);
List<GatewayFilter> gatewayFilters = route.getFilters();
List<GatewayFilter> combined = new ArrayList<>(this.globalFilters);
combined.addAll(gatewayFilters);
// TODO: needed or cached?
AnnotationAwareOrderComparator.sort(combined);
if (logger.isDebugEnabled()) {
logger.debug("Sorted gatewayFilterFactories: " + combined);
}
return new DefaultGatewayFilterChain(combined).filter(exchange);
}
13.RoutePredicateHandlerMapping
gateway独有的，实现了HandlerMapping接口，查找handler时，将查找RouteLocator里面的匹配的Route，将route存入exchange里面，用于构造FilteringWebHandler。
14.逻辑图
总结
以上就是gateway使用到的主要类，因为gateway是基于springWebFlux实现的，所以流程还是webFlux的流程，gateway对其进行扩充，使用十个globleFilter实现了网关功能。
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