SpringCloud gateway如何修改返回数据

plugins {
    id 'org.springframework.boot' version '2.1.6.RELEASE'
    id 'java'
    id "io.freefair.lombok" version "3.6.6"
}apply plugin: 'io.spring.dependency-management'group = 'cn.buddie.demo'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '11'repositories {
    mavenCentral()
}ext {
    set('springCloudVersion', "Greenwich.SR2")
}dependencies {
    implementation 'org.springframework.cloud:spring-cloud-starter-gateway'
    compile 'org.projectlombok:lombok:1.18.8'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}dependencyManagement {
    imports {
        mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
    }
}

spring:
  cloud:
    gateway:
      enabled: true
      routes:
      - id: test-route
        uri: http://127.0.0.1:8123/users
        predicates:
        - Path=/users
        filters:
        - UnionResult

package cn.buddie.demo.springcloudgateway.filter;import cn.buddie.demo.springcloudgateway.model.UnionResult;
import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.factory.rewrite.ModifyResponseBodyGatewayFilterFactory;
import org.springframework.cloud.gateway.filter.factory.rewrite.RewriteFunction;
import org.springframework.stereotype.Component;
import reactor.core.publisher.Mono;
@Component
public class UnionResultGatewayFilterFactory extends ModifyResponseBodyGatewayFilterFactory {
    @Override
    public GatewayFilter apply(Config config) {
        return new ModifyResponseGatewayFilter(this.getConfig());
    }
    private Config getConfig() {
        Config cf = new Config();
        // Config.setRewriteFunction(Class<T> inClass, Class<R> outClass, RewriteFunction<T, R> rewriteFunction)
        // inClass 原数据类型，可以指定为具体数据类型，我这里指定为Object,是为了处理多种数据类型。
        //                      当然支持多接口返回多数据类型的统一修改，yaml中的配置，path,uri需要做相关调整
        // outClass 目标数据类型
        // rewriteFunction 内容重写方法
        cf.setRewriteFunction(Object.class, UnionResult.class, getRewriteFunction());
        return cf;
    }    private RewriteFunction<Object, UnionResult> getRewriteFunction() {
        return (exchange, resp) -> Mono.just(UnionResult.builder().requestId(exchange.getRequest().getHeaders().getFirst("cn-buddie.demo.requestId")).result(resp).build());
    }
}

package cn.buddie.demo.springcloudgateway.model;import lombok.Builder;
import lombok.Getter;
import lombok.Setter;
@Getter
@Setter
@Builder
public class UnionResult {
    private String requestId;
    private Object result;
}

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<Void> 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;
 }
}

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;
public class ResponseDecorator extends ServerHttpResponseDecorator{
 public ResponseDecorator(ServerHttpResponse delegate){
  super(delegate);
 } @Override
 @SuppressWarnings(value = "unchecked")
 public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {  if(body instanceof Flux) {
   Flux<DataBuffer> fluxBody = (Flux<DataBuffer>) 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();
 }
}