场景： 前端传来了一个大的字符串 发现请求不通 一番调试发现SpringGateway 默认内存缓冲区262144字节
网上查了很多种常见的解决方案无效之后 直接重写底层

网友的解决方案

方案1（无效）

直接修改缓冲区大小

spring:codec:max-in-memory-size: 1048576

方案2（无效）

方案3 无效

gateway-2.2.3以上版本修复了该bug，在GatewayAutoConfiguration中加入了配置写入，但只限ReadBodyPredicateFactory类，如自定义类型需要使用方案二。

package org.springframework.cloud.gateway.handler.predicate;
...
public class ReadBodyPredicateFactoryextends AbstractRoutePredicateFactory<ReadBodyPredicateFactory.Config> {
...private final List<HttpMessageReader<?>> messageReaders;public ReadBodyPredicateFactory() {super(Config.class);this.messageReaders = HandlerStrategies.withDefaults().messageReaders();}/*** GatewayAutoConfiguration初始化配置写入相关配置*/public ReadBodyPredicateFactory(List<HttpMessageReader<?>> messageReaders) {super(Config.class);this.messageReaders = messageReaders;}
...}

方案4（无效）

重写ReadBodyPredicateFactory，注入ServerCodecConfigurer，使用ServerCodecConfigurer.getReaders()获取相关配置。

...
/*** @description: 自定义ReadBodyPredicateFactory，copy之ReadBodyPredicateFactory* @author: lizz* @date: 2020/6/8 14:22*/
@Component
public class GwReadBodyPredicateFactory extends AbstractRoutePredicateFactory<GwReadBodyPredicateFactory.Config> {/*** 获取Spring配置，解决最大body问题*/@AutowiredServerCodecConfigurer codecConfigurer;@Override@SuppressWarnings("unchecked")public AsyncPredicate<ServerWebExchange> applyAsync(GwReadBodyPredicateFactory.Config config) {
...return new AsyncPredicate<ServerWebExchange>() {@Overridepublic Publisher<Boolean> apply(ServerWebExchange exchange) {return ServerWebExchangeUtils.cacheRequestBodyAndRequest(exchange,(serverHttpRequest) -> ServerRequest.create(exchange.mutate().request(serverHttpRequest).build(), codecConfigurer.getReaders()).bodyToMono(inClass).doOnNext(objectValue -> exchange.getAttributes().put(CACHE_REQUEST_BODY_OBJECT_KEY, objectValue)).map(objectValue -> config.getPredicate().test(objectValue)));
...
}

方案5 有效

直接重写SpringGateway底层处理请求请求的 

org.springframework.core.codec.AbstractDataBufferDecoder类

/** Copyright 2002-2019 the original author or authors.** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at**      https://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/package org.springframework.core.codec;import java.util.Map;import org.reactivestreams.Publisher;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;import org.springframework.core.ResolvableType;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.MimeType;/*** 重写SpringWebFex底层 为了解决GateWay报错：Exceeded limit on max bytes to buffer : 262144 错误* Abstract base class for {@code Decoder} implementations that can decode* a {@code DataBuffer} directly to the target element type.** <p>Sub-classes must implement {@link #decodeDataBuffer} to provide a way to* transform a {@code DataBuffer} to the target data type. The default* {@link #decode} implementation transforms each individual data buffer while* {@link #decodeToMono} applies "reduce" and transforms the aggregated buffer.** <p>Sub-classes can override {@link #decode} in order to split the input stream* along different boundaries (e.g. on new line characters for {@code String})* or always reduce to a single data buffer (e.g. {@code Resource}).** @author Rossen Stoyanchev* @since 5.0* @param <T> the element type*/
@SuppressWarnings("deprecation")
public abstract class AbstractDataBufferDecoder<T> extends AbstractDecoder<T> {private int maxInMemorySize = 256 * 1024*10;protected AbstractDataBufferDecoder(MimeType... supportedMimeTypes) {super(supportedMimeTypes);}/*** Configure a limit on the number of bytes that can be buffered whenever* the input stream needs to be aggregated. This can be a result of* decoding to a single {@code DataBuffer},* {@link java.nio.ByteBuffer ByteBuffer}, {@code byte[]},* {@link org.springframework.core.io.Resource Resource}, {@code String}, etc.* It can also occur when splitting the input stream, e.g. delimited text,* in which case the limit applies to data buffered between delimiters.* <p>By default this is set to 256K.* @param byteCount the max number of bytes to buffer, or -1 for unlimited* @since 5.1.11*/public void setMaxInMemorySize(int byteCount) {this.maxInMemorySize = byteCount;}/*** Return the {@link #setMaxInMemorySize configured} byte count limit.* @since 5.1.11*/public int getMaxInMemorySize() {return this.maxInMemorySize;}@Overridepublic Flux<T> decode(Publisher<DataBuffer> input, ResolvableType elementType,@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {return Flux.from(input).map(buffer -> decodeDataBuffer(buffer, elementType, mimeType, hints));}@Overridepublic Mono<T> decodeToMono(Publisher<DataBuffer> input, ResolvableType elementType,@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {return DataBufferUtils.join(input, this.maxInMemorySize).map(buffer -> decodeDataBuffer(buffer, elementType, mimeType, hints));}/*** How to decode a {@code DataBuffer} to the target element type.* @deprecated as of 5.2, please implement* {@link #decode(DataBuffer, ResolvableType, MimeType, Map)} instead*/@Deprecated@Nullableprotected T decodeDataBuffer(DataBuffer buffer, ResolvableType elementType,@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {return decode(buffer, elementType, mimeType, hints);}}