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Gateway 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：
实现
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()); } 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;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(); }}感谢各位的阅读，以上就是“Spring Cloud Gateway怎么修改HTTP响应信息”的内容了，经过本文的学习后，相信大家对Spring Cloud Gateway怎么修改HTTP响应信息这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是编程网，小编将为大家推送更多相关知识点的文章，欢迎关注！
