Spring Cloud Gateway 如何修改HTTP响应信息

Spring Cloud Gateway 如何修改HTTP响应信息

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 {

prihttp://vate 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 filter(ServerWebExchange exchange, GatewayFilterChain chain) {

return processResponse(exchange, chain);

}

private Mono 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 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 rawBody = clientResponse.bodyToMono(String.class).map(s -> s);

BodyInserter, 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 messageBody = outputMessage.getBody();

Flux 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 http://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 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 getBody() {

return flux;

}

@Override

public HttpHeaders getHeaders() {

return headers;

}

@Override

public HttpStatus getStatusCode() {

return null;

}

@Override

public int getRawStatusCode() {

cDXoRszB return 0;

}

@Override

public MultiValueMap 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;

@Component

public class RequestGlobalFilter implements GlobalFilter, Ordered {

//...

@Override

public Mono 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 writeWith(Publisher extends DataBuffer> body) {

if(body instanceof Flux) {

Flux fluxBody = (Flux) 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();

}

}

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