Spring Cloud Gateway 修改请求体、响应体

在Spring Cloud Gateway中，修改请求体和响应体可以通过自定义过滤器来实现。以下是一个简单的例子，展示如何创建一个自定义过滤器来修改请求体和响应体。

1. 创建一个自定义的Gateway过滤器工厂：

import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferFactory;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.http.server.reactive.ServerHttpRequestDecorator;
import org.springframework.http.server.reactive.ServerHttpResponseDecorator;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
 
import java.nio.charset.StandardCharsets;
 
@Component
public class ModifyBodyGatewayFilterFactory extends AbstractGatewayFilterFactory<ModifyBodyGatewayFilterFactory.Config> {
    public ModifyBodyGatewayFilterFactory() {
        super(Config.class);
    }
 
    @Override
    public GatewayFilter apply(Config config) {
        return (exchange, chain) -> {
            // 修改请求体
            ServerHttpRequestDecorator decorator = new ServerHttpRequestDecorator(exchange.getRequest()) {
                @Override
                public Flux<DataBuffer> getBody() {
                    // 返回修改后的数据
                    return Flux.just(exchange.getResponse().bufferFactory().wrap(config.modifyRequestBody().getBytes()));
                }
            };
            exchange = exchange.mutate().request(decorator).build();
 
            // 修改响应体
            ServerHttpResponseDecorator responseDecorator = new ServerHttpResponseDecorator(exchange.getResponse()) {
                @Override
                public Mono<Void> writeWith(Flux<? extends DataBuffer> body) {
                    // 在这里可以对响应体进行修改，但是注意这里的body已经被读取了，如果需要读取和修改，需要使用cache()操作符
                    return super.writeWith(body.map(buffer -> {
                        byte[] content = new byte[buffer.readableByteCount()];
                        buffer.read(content);
                        // 修改响应内容
                        byte[] modifiedContent = config.modifyResponseBody(new String(content, StandardCharsets.UTF_8)).getBytes(StandardCharsets.UTF_8);
                        DataBuffer modifiedBuffer = exchange.getResponse().bufferFactory().wrap(modifiedContent