我们公司最近在升级springCloud2.X，由于Spring-Cloud-Gateway为官方推荐使用，所以最近在研究Spring-Cloud-Gateway，但是在实际开发过程中遇到了种种问题，其中耗时最长的为获取multipart/form-data里面的json字符串，在网上尝试了各种解决方案都无法成功获取，最终在GitHub的issue找到了一个大佬将此问题解决，废话不多说，直接上代码：

package com.XXX.center.gateway.filter;

import java.util.Collections;
import java.util.List;

import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.core.ResolvableType;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.codec.HttpMessageReader;
import org.springframework.http.codec.multipart.FormFieldPart;
import org.springframework.http.codec.multipart.Part;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpRequestDecorator;
import org.springframework.stereotype.Component;
import org.springframework.util.MultiValueMap;
import org.springframework.web.reactive.function.server.HandlerStrategies;
import org.springframework.web.server.ServerWebExchange;

import com.XX.center.gateway.entity.GatewayContext;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

/**
 * 获取请求内容.
 * 此版本为是优化后的，在之前的版本中读取文件速度会变得很慢，导致响应时间过长。
 *
 * @author zyb
 */
@Component
public class GatewayContextFilter extends BaseFilter {

    /**
     * default HttpMessageReader.
     */
    private static final List<HttpMessageReader<?>> MESSAGE_READERS = HandlerStrategies.withDefaults().messageReaders();

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        final ServerHttpRequest request = exchange.getRequest();
        final String path = request.getPath().pathWithinApplication().value();
        // GatewayContext中目前只有一个String的path和String的requestBody，如果需要别的参数在GatewayContext中追加即可，因为这只是一个实体类，所以就不放源码了，各位需要什么就往里面放什么即可
        final GatewayContext gatewayContext = new GatewayContext();
        gatewayContext.setPath(path);
        // GatewayContext.CACHE_GATEWAY_CONTEXT是一个常量定义，至于常量的值是什么，只要保证key值唯一即可，各位随便定义
        // 此处的作用为将我们需要的值放入Attributes中，以便在别的filter中使用，如果需要在别的地方使用，只需要exchange.getAttributes.get(GatewayContext.CACHE_GATEWAY_CONTEXT)即可
        exchange.getAttributes().put(GatewayContext.CACHE_GATEWAY_CONTEXT, gatewayContext);
        return DataBufferUtils.join(exchange.getRequest().getBody()).flatMap(dataBuffer -> {
            DataBufferUtils.retain(dataBuffer);
            final Flux<DataBuffer> cachedFlux = Flux.defer(() -> Flux.just(dataBuffer.slice(0, dataBuffer.readableByteCount())));
            final ServerHttpRequest mutatedRequest = new ServerHttpRequestDecorator(exchange.getRequest()) {
                @Override
                public Flux<DataBuffer> getBody() {
                    return cachedFlux;
                }
            };
            final ServerWebExchange mutatedExchange = exchange.mutate().request(mutatedRequest).build();
            return cacheBody(mutatedExchange, chain, gatewayContext);
        });
    }

    @SuppressWarnings("unchecked")
    private Mono<Void> cacheBody(ServerWebExchange exchange, GatewayFilterChain chain, GatewayContext gatewayContext) {
        final HttpHeaders headers = exchange.getRequest().getHeaders();
        if (headers.getContentLength() == 0) {
            return chain.filter(exchange);
        }
        final ResolvableType resolvableType;
        if (MediaType.MULTIPART_FORM_DATA.isCompatibleWith(headers.getContentType())) {
            resolvableType = ResolvableType.forClassWithGenerics(MultiValueMap.class, String.class, Part.class);
        } else {
            resolvableType = ResolvableType.forClass(String.class);
        }
        return MESSAGE_READERS.stream().filter(reader -> reader.canRead(resolvableType, exchange.getRequest().getHeaders().getContentType())).findFirst()
            .orElseThrow(() -> new IllegalStateException("no suitable HttpMessageReader.")).readMono(resolvableType, exchange.getRequest(), Collections.emptyMap()).flatMap(resolvedBody -> {
                if (resolvedBody instanceof MultiValueMap) {
                    final Part partInfo = (Part) ((MultiValueMap) resolvedBody).getFirst("info");
                    if (partInfo instanceof FormFieldPart) {
                        gatewayContext.setRequestBody(((FormFieldPart) partInfo).value());
                    }
                } else {
                    gatewayContext.setRequestBody((String) resolvedBody);
                }
                return chain.filter(exchange);
            });
    }
}

参考：https://github.com/xurui8691413/sping-cloud-gateway-read-multipart-filter/blob/master/spring-cloud-gateway-sample

望能帮助到大家