實踐Spring Cloud的過程中，使用Gateway作為路由組件，并且基于Gateway實現權限的驗證、攔截、過濾，對于下游微服務的響應結果，我們總會有需要修改以統一數據格式，或者修改過濾用戶沒有權限看到的數據信息，這時候就需要有一個能夠修改響應體的Filter。

Spring Cloud Gateway 版本為2.1.0

在當前版本，ModifyRequestBodyGatewayFilterFactory是官方提供的修改響應體的參考類，This filter is BETA and may be subject to change in a future release.，類的注釋中說明這個類在以后版本中會改進，實際使用可以參考實現功能，但是性能影響較大，不過沒有別的選擇還是得選擇這個。

官方文檔：

最終代碼

先貼最終代碼

public class ResponseDecryptionGlobalFilter implements GlobalFilter, Ordered { private static Logger log = LoggerFactory.getLogger(ResponseDecryptionGlobalFilter.class); @Override public int getOrder() { // 控制在NettyWriteResponseFilter后執行return NettyWriteResponseFilter.WRITE_RESPONSE_FILTER_ORDER - 1; } @Override public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {return processResponse(exchange, chain); } private Mono<Void> processResponse(ServerWebExchange exchange, GatewayFilterChain chain) {// 路由中如果不需要過濾則不進行過濾if (!BooleanUtils.isTrue()) { return chain.filter(exchange);}ServerHttpResponseDecorator responseDecorator = new ServerHttpResponseDecorator(exchange.getResponse()) { @Override public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {String originalResponseContentType = exchange.getAttribute(ORIGINAL_RESPONSE_CONTENT_TYPE_ATTR);HttpHeaders httpHeaders = new HttpHeaders();httpHeaders.add(HttpHeaders.CONTENT_TYPE, originalResponseContentType);ResponseAdapter responseAdapter = new ResponseAdapter(body, httpHeaders);DefaultClientResponse clientResponse = new DefaultClientResponse(responseAdapter, ExchangeStrategies.withDefaults());Mono<String> rawBody = clientResponse.bodyToMono(String.class).map(s -> s);BodyInserter<Mono<String>, ReactiveHttpOutputMessage> bodyInserter = BodyInserters.fromPublisher(rawBody, String.class);CachedBodyOutputMessage outputMessage = new CachedBodyOutputMessage(exchange, exchange.getResponse().getHeaders());return bodyInserter.insert(outputMessage, new BodyInserterContext()).then(Mono.defer(() -> { Flux<DataBuffer> messageBody = outputMessage.getBody(); Flux<DataBuffer> flux = messageBody.map(buffer -> {CharBuffer charBuffer = StandardCharsets.UTF_8.decode(buffer.asByteBuffer());DataBufferUtils.release(buffer);// 將響應信息轉化為字符串String responseStr = charBuffer.toString();if (StringUtils.isNotBlank(responseStr)) { try {JSONObject result = JSONObject.parseObject(responseStr);System.out.println(dataFilter(result));if (result.containsKey('data')) { responseStr = dataFilter(result);} else { log.error('響應結果序列化異常:{}', responseStr);} } catch (JSONException e) {log.error('響應結果序列化異常:{}', responseStr); }}return getDelegate().bufferFactory().wrap(responseStr.getBytes(StandardCharsets.UTF_8)); }); HttpHeaders headers = getDelegate().getHeaders(); // 修改響應包的大小，不修改會因為包大小不同被瀏覽器丟掉 flux = flux.doOnNext(data -> headers.setContentLength(data.readableByteCount())); return getDelegate().writeWith(flux);})); }};return chain.filter(exchange.mutate().response(responseDecorator).build()); } /** * 權限數據過濾 * * @param result * @return */ private String dataFilter(JSONObject result) {Object data = result.get('data');return result.toJSONString(); } private class ResponseAdapter implements ClientHttpResponse {private final Flux<DataBuffer> flux;private final HttpHeaders headers;@SuppressWarnings('unchecked')private ResponseAdapter(Publisher<? extends DataBuffer> body, HttpHeaders headers) { this.headers = headers; if (body instanceof Flux) {flux = (Flux) body; } else {flux = ((Mono) body).flux(); }}@Overridepublic Flux<DataBuffer> getBody() { return flux;}@Overridepublic HttpHeaders getHeaders() { return headers;}@Overridepublic HttpStatus getStatusCode() { return null;}@Overridepublic int getRawStatusCode() { return 0;}@Overridepublic MultiValueMap<String, ResponseCookie> getCookies() { return null;} }}踩過的坑 響應體報文過大: 起初直接讀取buffer的響應信息，包小的情況沒有問題，但是包大了會拋出json無法轉換異常，因為沒能讀取完整的響應內容，參考ModifyRequestBodyGatewayFilter，等待buffer全部讀完再轉為數組，然后執行處理。本質原因是底層的Reactor-Netty的數據塊讀取大小限制導致獲取到的DataBuffer實例里面的數據是不完整的。 修改響應信息后，響應的ContentLength會發生變化，忘記修改response中的Content-Length長度，導致前端請求無法獲取修改后的響應結果。

flux = flux.doOnNext(data -> headers.setContentLength(data.readableByteCount())); order值必須小于-1，因為覆蓋返回響應體，自定義的GlobalFilter必須比NettyWriteResponseFilter處理完后執行。order越小越早進行處理，越晚處理響應結果。理解ServerWebExchange

先看ServerWebExchange的注釋：

Contract for an HTTP request-response interaction. Provides access to the HTTP request and response and also exposes additional server-side processing related properties and features such as request attributes.

翻譯一下大概是：

ServerWebExchange是一個**HTTP請求-響應交互的契約。**提供對HTTP請求和響應的訪問，并公開額外的服務器端處理相關屬性和特性，如請求屬性。

ServerWebExchange有點像Context的角色，我把它理解為http請求信息在Filter透傳的容器，之所以稱之為容器，因為它可以存儲我們像放進去的數據。

注意：

ServerHttpRequest是一個只讀類，因此需要通過下面例子的方法來進行修改，對于讀多寫少的場景，這種設計模式是值得借鑒的

ServerHttpRequest newRequest = request.mutate().headers('key','value').path('/myPath').build();ServerWebExchange newExchange = exchange.mutate().response(responseDecorator).build();Gateway 修改返回的響應體問題描述：

在gateway中修改返回的響應體，在全局Filter中添加如下代碼：

import org.springframework.core.Ordered;import org.springframework.cloud.gateway.filter.GlobalFilter;import org.springframework.cloud.gateway.filter.GatewayFilterChain;import org.springframework.stereotype.Component;import org.springframework.web.server.ServerWebExchange;import reactor.core.publisher.Mono;@Componentpublic class RequestGlobalFilter implements GlobalFilter, Ordered { //... @Override public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) { //... ResponseDecorator decorator = new ResponseDecorator(exchange.getResponse()); return chain.filter(exchange.mutate().response(decorator).build()); } @Override public int getOrder() { return -1000; }}

通過.response(decorator)設置一個響應裝飾器（自定義），以下是裝飾器具體實現：

import cn.hutool.json.JSONObject;import org.reactivestreams.Publisher;import org.springframework.core.io.buffer.DataBuffer;import org.springframework.core.io.buffer.DataBufferFactory;import org.springframework.core.io.buffer.DataBufferUtils;import org.springframework.core.io.buffer.DefaultDataBufferFactory;import org.springframework.http.server.reactive.ServerHttpResponse;import org.springframework.http.server.reactive.ServerHttpResponseDecorator;import reactor.core.publisher.Flux;import reactor.core.publisher.Mono;import java.nio.charset.Charset;/** * @author visy.wang * @desc 響應裝飾器（重構響應體） */public class ResponseDecorator extends ServerHttpResponseDecorator{ public ResponseDecorator(ServerHttpResponse delegate){ super(delegate); } @Override @SuppressWarnings(value = 'unchecked') public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) { if(body instanceof Flux) { Flux<DataBuffer> fluxBody = (Flux<DataBuffer>) body; return super.writeWith(fluxBody.buffer().map(dataBuffers -> { DataBufferFactory dataBufferFactory = new DefaultDataBufferFactory(); DataBuffer join = dataBufferFactory.join(dataBuffers); byte[] content = new byte[join.readableByteCount()]; join.read(content); DataBufferUtils.release(join);// 釋放掉內存String bodyStr = new String(content, Charset.forName('UTF-8'));//修改響應體 bodyStr = modifyBody(bodyStr); getDelegate().getHeaders().setContentLength(bodyStr.getBytes().length); return bufferFactory().wrap(bodyStr.getBytes()); })); } return super.writeWith(body); } //重寫這個函數即可 private String modifyBody(String jsonStr){ JSONObject json = new JSONObject(jsonStr);//TODO...修改響應體 return json.toString(); }}

以上為個人經驗，希望能給大家一個參考，也希望大家多多支持好吧啦網。