WebFlux（reactor）中获取完整response body数据

场景
使用Spring Cloud Gateway（SCG）时，想在网关日志中输出返回日志，但由于数据流只能被读取一次，必须使用特定方式进行重写才能正常返回到前端。

处理过程
起初使用fluxBody.map读取数据流，会出现多次输出的情况，由于使用的时reactor框架处理数据，导致会出现将一个结果集分为多次处理，会执行多次map，效果不理想。
Flux<? extends DataBuffer> fluxBody = (Flux<? extends DataBuffer>) body;
Mono<Void> newMono = super.writeWith(
fluxBody.map(dataBuffer -> {
String respBody = dataBuffer.toString(StandardCharsets.UTF_8);
if (respBody.length() > maxLogLength) {
respBody = respBody.substring(0, maxLogLength);
}
if (PathUtil.checkPath(request.getPath().value(), contentLengthUrls)) {
httpHeaders.setContentLength(respBody.length());
}
//匹配是否需要生成slat
if (PathUtil.checkPath(request.getPath().value(), loginUrls)) {
String salt = createSlat(JSON.parseObject(respBody).getString("token"));
if (StringUtils.isEmpty(salt)) {
logger.warn("CreateSalt error:id={}", request.getHeaders().getFirst(HEADER_REQUEST_ID));
} else {
httpHeaders.add("s", salt);
}
}
logger.info("fgwResponse : id={},body = {}", request.getHeaders().getFirst(HEADER_REQUEST_ID), respBody);
return bufferFactory.wrap(content);
})
);
//request中有salt则返回到response中
logger.info("fgwResponse : id={},resp = {}", request.getHeaders().getFirst(HEADER_REQUEST_ID), JSON.toJSONString(exchange.getResponse()));
return newMono;
最后查看github上的讨论，开发者给出DataBufferUtils.join(body) .doOnNext的方式。
@Component
public class LogRespFilter implements GlobalFilter, Ordered {

@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
ServerHttpResponse originalResponse = exchange.getResponse();
ServerHttpRequest request = exchange.getRequest();
ServerHttpResponseDecorator decoratedResponse = new ServerHttpResponseDecorator(originalResponse) {
@Override
public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
//修改header
HttpHeaders httpHeaders = originalResponse.getHeaders();
httpHeaders.add("xxxxxx","aaaaaa");
//输出返回结果
if (body instanceof Flux) {
Mono<Void> newMono = super.writeWith(
DataBufferUtils.join(body)
.doOnNext(dataBuffer -> {
String respBody = dataBuffer.toString(StandardCharsets.UTF_8);
//输出body
logger.info("fgwResponse : body = {}", respBody);
})
);
//输出response，不包含body
logger.info("fgwResponse : resp = {}", JSON.toJSONString(exchange.getResponse()));
return newMono;

}
return super.writeWith(body);
}
};
return chain.filter(exchange.mutate().response(decoratedResponse).build());
}
}

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原文链接：https://blog.csdn.net/lizz861109/article/details/106303929