SpringCloud gateway How to Modify Returned Data

Version description

开源软件	版本
springboot	2.1.6.RELEASE
jdk	11.0.3

gradle

springboot 2.1 and lombok are mainly introduced

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}"
    }
}

yaml

Define the route and filter test-route route. When Path is/users, go to the link http://127.0.0.1: 8123/users configured in uri. Use UnionResult to filter

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

filter

The name of filter configured in yaml, plus "GatewayFilterFactory", is the corresponding filter Java class

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;/**
 * description
 *
 * @author buddie.wei
 * @date 2019/7/20
 */
@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  The original data type can be specified as a specific data type, which I specify here as Object, Is to deal with multiple data types. 
        //                       Of course, it supports multi-interface to return multi-data type system 1 Modify, yaml Configuration in, path,uri Need to make relevant adjustments 
        // outClass  Target data type 
        // rewriteFunction  Content rewriting method 
        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());
    }
}

model

package cn.buddie.demo.springcloudgateway.model;import lombok.Builder;
import lombok.Getter;
import lombok.Setter;/**
 * description
 *
 * @author buddie.wei
 * @date 2019/7/20
 */
@Getter
@Setter
@Builder
public class UnionResult {
    private String requestId;
    private Object result;
}

SpringCloud gateway Modify the returned response body

Problem description:

Modify the returned response body in gateway and add the following code in the global Filter:

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;
 }
}

Set up a response decorator (custom) via. response (decorator), and the following is the concrete implementation of the decorator:

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  Response decorator (reconstruct response body) 
 */
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);//  Release memory 
    
    String bodyStr = new String(content, Charset.forName("UTF-8"));                // Modify the response body 
    bodyStr = modifyBody(bodyStr);    getDelegate().getHeaders().setContentLength(bodyStr.getBytes().length);
    return bufferFactory().wrap(bodyStr.getBytes());
   }));
  }
  return super.writeWith(body);
 }    // You can override this function 
 private String modifyBody(String jsonStr){
  JSONObject json = new JSONObject(jsonStr);
        //TODO... Modify the response body 
  return json.toString();
 }
}