Spring Cloud Gateway 如何修改HTTP响应信息

实践Spring Cloud的过程中，使用Gateway作为路由组件，并且基于Gateway实现权限的验证、拦截、过滤，对于下游微服务的响应结果，我们总会有需要修改以统一数据格式，或者修改过滤用户没有权限看到的数据信息，这时候就需要有一个能够修改响应体的Filter。

Spring Cloud Gateway 版本为2.1.0

在当前版本，ModifyRequestBodyGatewayFilterFactory是官方提供的修改响应体的参考类，This filter is BETA and may be subject to change in a future release.，类的注释中说明这个类在以后版本中会改进，实际使用可以参考实现功能，但是性能影响较大，不过没有别的选择还是得选择这个。

官方文档：

最终代码

先贴最终代码

public class ResponseDecryptionGlobalFilter implements GlobalFilter, Ordered { private static Logger log = LoggerFactory.getLogger(ResponseDecryptionGlobalFilter.class); @Override public int getOrder() { // 控制在NettyWriteResponseFilter后执行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) {// 路由中如果不需要过滤则不进行过滤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);// 将响应信息转化为字符串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('响应结果序列化异常:{}', responseStr);} } catch (JSONException e) {log.error('响应结果序列化异常:{}', responseStr); }}return getDelegate().bufferFactory().wrap(responseStr.getBytes(StandardCharsets.UTF_8)); }); HttpHeaders headers = getDelegate().getHeaders(); // 修改响应包的大小，不修改会因为包大小不同被浏览器丢掉 flux = flux.doOnNext(data -> headers.setContentLength(data.readableByteCount())); return getDelegate().writeWith(flux);})); }};return chain.filter(exchange.mutate().response(responseDecorator).build()); } /** * 权限数据过滤 * * @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;} }}踩过的坑 响应体报文过大: 起初直接读取buffer的响应信息，包小的情况没有问题，但是包大了会抛出json无法转换异常，因为没能读取完整的响应内容，参考ModifyRequestBodyGatewayFilter，等待buffer全部读完再转为数组，然后执行处理。本质原因是底层的Reactor-Netty的数据块读取大小限制导致获取到的DataBuffer实例里面的数据是不完整的。 修改响应信息后，响应的ContentLength会发生变化，忘记修改response中的Content-Length长度，导致前端请求无法获取修改后的响应结果。

flux = flux.doOnNext(data -> headers.setContentLength(data.readableByteCount())); order值必须小于-1，因为覆盖返回响应体，自定义的GlobalFilter必须比NettyWriteResponseFilter处理完后执行。order越小越早进行处理，越晚处理响应结果。理解ServerWebExchange

先看ServerWebExchange的注释：

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.

翻译一下大概是：

ServerWebExchange是一个**HTTP请求-响应交互的契约。**提供对HTTP请求和响应的访问，并公开额外的服务器端处理相关属性和特性，如请求属性。

ServerWebExchange有点像Context的角色，我把它理解为http请求信息在Filter透传的容器，之所以称之为容器，因为它可以存储我们像放进去的数据。

注意：

ServerHttpRequest是一个只读类，因此需要通过下面例子的方法来进行修改，对于读多写少的场景，这种设计模式是值得借鉴的

ServerHttpRequest newRequest = request.mutate().headers('key','value').path('/myPath').build();ServerWebExchange newExchange = exchange.mutate().response(responseDecorator).build();Gateway 修改返回的响应体问题描述：

在gateway中修改返回的响应体，在全局Filter中添加如下代码：

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; }}

通过.response(decorator)设置一个响应装饰器（自定义），以下是装饰器具体实现：

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 响应装饰器（重构响应体） */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);// 释放掉内存String bodyStr = new String(content, Charset.forName('UTF-8'));//修改响应体 bodyStr = modifyBody(bodyStr); getDelegate().getHeaders().setContentLength(bodyStr.getBytes().length); return bufferFactory().wrap(bodyStr.getBytes()); })); } return super.writeWith(body); } //重写这个函数即可 private String modifyBody(String jsonStr){ JSONObject json = new JSONObject(jsonStr);//TODO...修改响应体 return json.toString(); }}

以上为个人经验，希望能给大家一个参考，也希望大家多多支持好吧啦网。