How to use ReadBodyPredicateFactory to cache payload data - spring

Question

I have Spring Boot microservice, and sending large payload using swagger. At the server I get only 15000 chars and reset 2000 chars are not read.
How can I use ReadBodyPredicateFactory to cache the body message text?
I am using springcloudgateway and added filters. In the filter in apply method I am trying to read the payload json using
DefaultServerRequest serverRequest = new DefaultServerRequest(exchange);
body = serverRequest.bodyToMono(String.class).toFuture().get();
Sometimes it hangs.
I tried with Flux and then i get only half message
Flux body = request.getBody();
body.subscribe(buffer -> {
try {
System.out.println("byte count:" +
buffer.readableByteCount());
byte[] bytes = new byte[buffer.readableByteCount()];
buffer.read(bytes);
DataBufferUtils.release(buffer);
String bodyString = new String(bytes, StandardCharsets.UTF_8);
sb.append(bodyString);
} catch (Exception e) {
e.printStackTrace();
}

Answer 1

Recently, I needed the similar thing in my application and I've found that it can be achieved by Spring Cloud Gateway built-in caching in ServerWebExchangeUtils
Before filters that use request content in some business cases, I created a filter that only forces content caching:
#Component
class CachingRequestBodyFilter extends AbstractGatewayFilterFactory<CachingRequestBodyFilter.Config> {
public CachingRequestBodyFilter() {
super(Config.class);
}
public GatewayFilter apply(final Config config) {
return (exchange, chain) -> ServerWebExchangeUtils.cacheRequestBody(exchange,
(serverHttpRequest) -> chain.filter(exchange.mutate().request(serverHttpRequest).build()));
}
public static class Config {
}
}
In any of the subsequent filters, we can extract the content of the request body, as below:
// some ReadRequestBodyFilter filter
public GatewayFilter apply(final Config config) {
return (exchange, chain) -> {
final var cachedBody = new StringBuilder();
final var cachedBodyAttribute = exchange.getAttribute(CACHED_REQUEST_BODY_ATTR);
if (!(cachedBodyAttribute instanceof DataBuffer)) {
// caching gone wrong error handling
}
final var dataBuffer = (DataBuffer) cachedBodyAttribute;
cachedBody.append(StandardCharsets.UTF_8.decode(dataBuffer.asByteBuffer()).toString());
final var bodyAsJson = cachedBody.toString();
// some processing
return chain.filter(exchange);
};
}
Then the gateway configuration would look like this:
spring:
cloud:
gateway:
routes:
- [...]
filters:
- CachingRequestBodyFilter
- ReadRequestBodyFilter