前言 Spring Cloud Gateway 是 Spring Cloud 新推出的网关框架，之前是 Netflix
1. 千万别依赖Undertow 我们在开发SpringBoot应用中都会把spring-web-starter默认依赖的Web容器Tomcat排除掉，并添加上undertow的依赖，使用undertow作为我们的Web运行容器。由于undertow与tomcat相比性能会更优一些，具体原因不再此赘述，感兴趣的同学可以看下这篇文章：https://www.jianshu.com/p/f7cb40a8ce22
1 2 3 4 return nettyOutbound.options(NettyPipeline.SendOptions::flushOnEach) .send(request.getBody() .map(dataBuffer -> ((NettyDataBuffer) dataBuffer) .getNativeBuffer()));
这里我们可以看到dataBuffer是直接强转成NettyDataBuffer类型，而当我们依赖中加入了undertow此处便为报类型转换异常，原因是因为Gateway基于NIO，而Undertow是基于BIO，而这里由于是undertow处理的请求，所以dataBuffer并不能强轩成NIO的NettyDataBuffer类型。所以注意，在Gateway项目中千万要记住不可再添加undertow依赖，否则你会发现，会有很多让你觉得不可思议的错误出现。
我们都知道InputStream只能允许我们读取一次，在我使用Gateway的过程中，由于需要在网关中执行一些用户鉴权的逻缉，而在一个获取账户明细的接口中，我们可以从请求头、Url请求参数、Form
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 @Slf4j @Component @Order(value = Ordered.HIGHEST_PRECEDENCE+2) public class AccountContextFilter implements WebFilter { private final static String TOKEN_PARAM_KEY = "access_token" ; @Override public Mono<Void> filter (ServerWebExchange exchange, WebFilterChain chain) { ServerHttpRequest request = exchange.getRequest(); HttpHeaders header = request.getHeaders(); String token = header.getFirst(AuthConstants.HEADER_AUTH); if (StringUtils.isBlank(token)) { token = request.getQueryParams().getFirst(TOKEN_PARAM_KEY); } } }
从上面的代码，我们可以很轻易的从exchange获取到的request对象中获取到请求头和Url请求参数，而当我想从FormData中取参时，却发现并不能轻易的调用取到参数。于是，通过查阅WebFlux官方API文档，找到了获取表单Body的方法，如下图：
1 2 3 4 5 exchange.getFormData().flatMap(formData->{ String token = formData.getFirst(TOKEN_PARAM_KEY); ... return chain.filter(exchange); });
以上方式看上去虽然麻烦了点，但还算是拿到了token，实现了鉴权的逻缉，但当过滤器执行完成后，进入到获取账户明细的Controller中时，我发现Form表单传的参数不见了，在Controller并不能接收到前端传过来的参数。此时，我便想到在Filter中取过一次FormData，应该问题出在此处。那么，该如何解决这个问题呢？我们想在Filter取到表单参数，又想在Controller中能够正常接收参数。于是，我便想到是否能够让这个FormData支持多次读取，而FormData是从exchange中取出来的，于是只要解决好Exchange这个对象就可以实现，决定对exchange再做一次封装。通过网上搜索，找到了网友对exchange二次封装的编码实现，下面直接出代码：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 @Slf4j public class PartnerServerHttpRequestDecorator extends ServerHttpRequestDecorator { private Flux<DataBuffer> body; PartnerServerHttpRequestDecorator(ServerHttpRequest delegate) { super (delegate); final String path = delegate.getURI().getPath(); final String query = delegate.getURI().getQuery(); final String method = Optional.ofNullable(delegate.getMethod()).orElse(HttpMethod.GET).name(); final String headers = delegate.getHeaders().entrySet() .stream() .map(entry -> " " + entry.getKey() + ": [" + String.join(";" , entry.getValue()) + "]" ) .collect(Collectors.joining("\n" )); final MediaType contentType = delegate.getHeaders().getContentType(); if (log.isDebugEnabled()) { log.debug("\n" + "HttpMethod : {}\n" + "Uri : {}\n" + "Headers : \n" + "{}" , method, path + (StrUtil.isEmpty(query) ? "" : "?" + query), headers); } Flux<DataBuffer> flux = super .getBody(); body = flux; } @Override public Flux<DataBuffer> getBody () { return body; } }
Response装饰类
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 public class PartnerServerHttpResponseDecorator extends ServerHttpResponseDecorator { PartnerServerHttpResponseDecorator(ServerHttpResponse delegate) { super (delegate); } @Override public Mono<Void> writeAndFlushWith (Publisher<? extends Publisher<? extends DataBuffer>> body) { return super .writeAndFlushWith(body); } @Override public Mono<Void> writeWith (Publisher<? extends DataBuffer> body) { return super .writeWith(body); } }
WebExchange装饰类
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 public class PayloadServerWebExchangeDecorator extends ServerWebExchangeDecorator { private PartnerServerHttpRequestDecorator requestDecorator; private PartnerServerHttpResponseDecorator responseDecorator; public PayloadServerWebExchangeDecorator (ServerWebExchange delegate) { super (delegate); requestDecorator = new PartnerServerHttpRequestDecorator (delegate.getRequest()); responseDecorator = new PartnerServerHttpResponseDecorator (delegate.getResponse()); } @Override public ServerHttpRequest getRequest () { return requestDecorator; } @Override public ServerHttpResponse getResponse () { return responseDecorator; } }
实现思路，其实很简单，通过封装ServerHttpRequestDecorator，将body作为成员变量缓存起来，方便后面随时获取调用。最后使用方式很简单，我采用的方式是直接新创建一个Filter在所有自定义过滤器之前执行，用来读取FormData，以便后面的Filter使用，代码如下：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 @Component @Order(value = Ordered.HIGHEST_PRECEDENCE) public class RequestBodyReadMoreFilter implements WebFilter { public final static String FORM_DATA_ATTR = "fromData" ; @Override public Mono<Void> filter (ServerWebExchange exchange, WebFilterChain chain) { PayloadServerWebExchangeDecorator payloadServerWebExchangeDecorator = new PayloadServerWebExchangeDecorator (exchange); MediaType mediaType = exchange.getRequest().getHeaders().getContentType(); if (MediaType.MULTIPART_FORM_DATA.isCompatibleWith(mediaType) || MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(mediaType)) { return payloadServerWebExchangeDecorator.getFormData().flatMap(formData->{ payloadServerWebExchangeDecorator.getAttributes().put(FORM_DATA_ATTR,formData); return chain.filter(payloadServerWebExchangeDecorator); }); } return chain.filter(payloadServerWebExchangeDecorator); } }
通过在exchange中setAttribute的方式，在后面的Filter中直接getAttribute()的方式，方便的取到表单数据完成校验逻缉。
3. @RequestParam无法接收post的FormData数据 这个问题也是很坑，通过查看WebFlux文档
https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html#webflux-ann-requestparam
The Servlet API “request parameter” concept conflates query parameters, form data, and multiparts into one. However,ServerWebExchange. While@RequestParambinds to query parameterscommand object .
文档中已经明确说明了webflux中，该注解仅支持url传参方式
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 @Configuration public class WebArgumentResolversConfig implements WebFluxConfigurer { @Autowired ConfigurableApplicationContext applicationContext; @Override public void configureArgumentResolvers (ArgumentResolverConfigurer configurer) { configurer.addCustomResolver(new FormDataMethodArgumentResolver (applicationContext.getBeanFactory(), ReactiveAdapterRegistry.getSharedInstance(), true )); } class FormDataMethodArgumentResolver extends RequestParamMethodArgumentResolver { public FormDataMethodArgumentResolver (ConfigurableBeanFactory factory, ReactiveAdapterRegistry registry, boolean useDefaultResolution) { super (factory, registry, useDefaultResolution); } @Override protected Object resolveNamedValue (String name, MethodParameter parameter, ServerWebExchange exchange) { MultiValueMap<String, String> requestParams = exchange.getRequest().getQueryParams(); Object value = resolveParameterByParam(name, parameter, requestParams); MultiValueMap<String,Object> formMap = (MultiValueMap<String,Object>)exchange.getAttributes().get(RequestBodyReadMoreFilter.FORM_DATA_ATTR); if (value == null && formMap != null ) { value = resolveParameterByForm(name, parameter, formMap); } return value; } private Object resolveParameterByParam (String name,MethodParameter parameter,MultiValueMap<String,String> data) { List<String> values = data.get(name); if (values != null && values.size() > 0 && parameter.getParameterType() == List.class) { return values; } else if (values != null && values.size() > 0 ) { return data.getFirst(name); } return null ; } private Object resolveParameterByForm (String name,MethodParameter parameter,MultiValueMap<String,Object> data) { List<Object> values = data.get(name); if (values != null && values.size() > 0 && parameter.getParameterType() == List.class) { return values; } else if (values != null && values.size() > 0 ) { return data.getFirst(name); } return null ; } } }
通过实现WebFluxConfigurer接口，将我们自定义的ArgumentResolver注册到配置中去，在获取FormData的方式上，也是延用了上述的方式，从exchange的attribute中去获取，然后剩下的就是表单K/V对的赋值逻缉实现了，这个比较简单，就不在此赘述了。
