SPRING INTEGRATION - ENRICH

package org.springframework.integration.stackoverflow.enricher;

import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.http.HttpMethod;
import org.springframework.integration.dsl.IntegrationFlow;
import org.springframework.integration.dsl.IntegrationFlows;
import org.springframework.integration.dsl.Transformers;
import org.springframework.integration.http.dsl.Http;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
public class SpringIntegrationEnricherApplication {

public static void main(String[] args) {
        SpringApplication.run(SpringIntegrationEnricherApplication.class, args);
    }

@Bean
    public IntegrationFlow jsonEnricherFlow(RestTemplate restTemplate) {
        return IntegrationFlows.from(Function.class)
                .transform(Transformers.fromJson(Map.class))
                .enrich((enricher) -> enricher
                        .<Map<String, ?>>requestPayload((message) ->
                                ((List<?>) message.getPayload().get("attributeIds"))
                                        .stream()
                                        .map(Object::toString)
                                        .collect(Collectors.joining(",")))
                        .requestSubFlow((subFlow) ->
                                subFlow.handle(
                                        Http.outboundGateway("/attributes?id={ids}", restTemplate)
                                                .httpMethod(HttpMethod.GET)
                                                .expectedResponseType(Map.class)
                                                .uriVariable("ids", "payload")))
                        .propertyExpression("attributes", "payload.attributes"))
                .<Map<String, ?>, Map<String, ?>>transform(
                        (payload) -> {
                            payload.remove("attributeIds");
                            return payload;
                        })
                .transform(Transformers.toJson())
                .get();
    }

}