As posted in the Spring Cloud Gateway Github issue mentioned by g00glen00b, until the library develops a Filter for this, I resolved it using the ModifyResponseBodyGatewayFilterFactory in my own custom Filter.
Just in case it's useful for anyone else, I provide the base implementation here (it may need some rework, but it should be enough to make the point).
Simply put, I have a "base" service retrieving something like this:
[
{
"targetEntryId": "624a448cbc728123b47d08c4",
"sections": [
{
"title": "sadasa",
"description": "asda"
}
],
"id": "624a448c45459c4d757869f1"
},
{
"targetEntryId": "624a44e5bc728123b47d08c5",
"sections": [
{
"title": "asda",
"description": null
}
],
"id": "624a44e645459c4d757869f2"
}
]
And I want to enrich these entries with the actual targetEntry data (of course, identified by targetEntryId).
So, I created my Filter based on the ModifyResponseBody one:
/**
* <p>
* Filter to compose a response body with associated data from a second API.
* </p>
*
* @author rozagerardo
*/
@Component
public class ComposeFieldApiGatewayFilterFactory extends
AbstractGatewayFilterFactory<ComposeFieldApiGatewayFilterFactory.Config> {
public ComposeFieldApiGatewayFilterFactory() {
super(Config.class);
}
@Autowired
ModifyResponseBodyGatewayFilterFactory modifyResponseBodyFilter;
ParameterizedTypeReference<List<Map<String, Object>>> jsonType =
new ParameterizedTypeReference<List<Map<String, Object>>>() {
};
@Value("${server.port:9080}")
int aPort;
@Override
public GatewayFilter apply(final Config config) {
return modifyResponseBodyFilter.apply((c) -> {
c.setRewriteFunction(List.class, List.class, (filterExchange, input) -> {
List<Map<String, Object>> castedInput = (List<Map<String, Object>>) input;
// extract base field values (usually ids) and join them in a "," separated string
String baseFieldValues = castedInput.stream()
.map(bodyMap -> (String) bodyMap.get(config.getOriginBaseField()))
.collect(Collectors.joining(","));
// Request to a path managed by the Gateway
WebClient client = WebClient.create();
return client.get()
.uri(UriComponentsBuilder.fromUriString("http://localhost").port(aPort)
.path(config.getTargetGatewayPath())
.queryParam(config.getTargetQueryParam(), baseFieldValues).build().toUri())
.exchangeToMono(response -> response.bodyToMono(jsonType)
.map(targetEntries -> {
// create a Map using the base field values as keys fo easy access
Map<String, Map> targetEntriesMap = targetEntries.stream().collect(
Collectors.toMap(pr -> (String) pr.get("id"), pr -> pr));
// compose the origin body using the requested target entries
return castedInput.stream().map(originEntries -> {
originEntries.put(config.getComposeField(),
targetEntriesMap.get(originEntries.get(config.getOriginBaseField())));
return originEntries;
}).collect(Collectors.toList());
})
);
});
});
}
;
@Override
public List<String> shortcutFieldOrder() {
return Arrays.asList("originBaseField", "targetGatewayPath", "targetQueryParam",
"composeField");
}
/**
* <p>
* Config class to use for AbstractGatewayFilterFactory.
* </p>
*/
public static class Config {
private String originBaseField;
private String targetGatewayPath;
private String targetQueryParam;
private String composeField;
public Config() {
}
// Getters and Setters...
}
}
For completeness, this is the corresponding route setup using my Filter:
spring:
cloud:
gateway:
routes:
# TARGET ENTRIES ROUTES
- id: targetentries_route
uri: ${configs.api.tagetentries.baseURL}
predicates:
- Path=/api/target/entries
- Method=GET
filters:
- RewritePath=/api/target/entries(?<segment>.*), /target-entries-service$\{segment}
# ORIGIN ENTRIES
- id: originentries_route
uri: ${configs.api.originentries.baseURL}
predicates:
- Path=/api/origin/entries**
filters:
- RewritePath=/api/origin/entries(?<segment>.*), /origin-entries-service$\{segment}
- ComposeFieldApi=targetEntryId,/api/target/entries,ids,targetEntry
And with this, my resulting response looks as follows:
[
{
"targetEntryId": "624a448cbc728123b47d08c4",
"sections": [
{
"title": "sadasa",
"description": "asda"
}
],
"id": "624a448c45459c4d757869f1",
"targetEntry": {
"id": "624a448cbc728123b47d08c4",
"targetEntityField": "whatever"
}
},
{
"targetEntryId": "624a44e5bc728123b47d08c5",
"sections": [
{
"title": "asda",
"description": null
}
],
"id": "624a44e645459c4d757869f2",
"targetEntry": {
"id": "624a44e5bc728123b47d08c5",
"targetEntityField": "somethingelse"
}
}
]
