Spring Cloud Gateway 如何修改HTTP響應信息

更新時間：2021年07月16日 09:18:22 作者：帷幄庸者

這篇文章主要介紹了Spring Cloud Gateway 修改HTTP響應信息的方式，具有很好的參考價值，希望對大家有所幫助。如有錯誤或未考慮完全的地方，望不吝賜教

Gateway 修改HTTP響應信息

實踐Spring Cloud的過程中，使用Gateway作為路由組件，并且基于Gateway實現(xiàn)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(tǒng)一數(shù)據(jù)格式，或者修改過濾用戶沒有權限看到的數(shù)據(jù)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(xiàn)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：

實現(xiàn)

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(zhí)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(shù)據(jù)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();
            }
        }
        @Override
        public Flux<DataBuffer> getBody() {
            return flux;
        }
        @Override
        public HttpHeaders getHeaders() {
            return headers;
        }
        @Override
        public HttpStatus getStatusCode() {
            return null;
        }
        @Override
        public int getRawStatusCode() {
            return 0;
        }
        @Override
        public 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(shù)組，然后執(zhí)行處理。本質原因是底層的Reactor-Netty的數(shù)據(jù)塊讀取大小限制導致獲取到的DataBuffer實例里面的數(shù)據(jù)是不完整的。
修改響應信息后，響應的ContentLength會發(fā)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(zhí)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(shù)據(jù)。

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;
@Component
public 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(xiàn)：

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(shù)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(jīng)驗，希望能給大家一個參考，也希望大家多多支持腳本之家。

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