How can I read Flux<DataBuffer> content? - spring-boot

Question

I want to read mulitpart/formdata, one part is application/JSON. I can't get them to Map<String,String>, Is there any way to parse Part to String?
private Map<String, String> getFormData(String path, MultiValueMap<String, Part> partMultiValueMap) {
if (partMultiValueMap != null) {
Map<String, String> formData = new HashMap<>();
Map<String, Part> multiPartMap = partMultiValueMap.toSingleValueMap();
for (Map.Entry<String, Part> partEntry : multiPartMap.entrySet()) {
Part part = partEntry.getValue();
if (part instanceof FormFieldPart) {
formData.put(partEntry.getKey(), ((FormFieldPart) part).value());
} else {
String bodyString = bufferToStr(part.content());
formData.put(partEntry.getKey(), bodyString);
}
}
return formData;
}
return null;
}
extra Flux
private String bufferToStr(Flux<DataBuffer> content){
AtomicReference<String> res = new AtomicReference<>();
content.subscribe(buffer -> {
byte[] bytes = new byte[buffer.readableByteCount()];
buffer.read(bytes);
DataBufferUtils.release(buffer);
res.set(new String(bytes, StandardCharsets.UTF_8));
});
return res.get();
}
Subscribe is async; bufferToStr value may be null?

Answer 1

You could do it in non-blocking way with StringDecoder
Basically you could write your code to return Mono<Map<>>
Note: I'm using Pair class here to return key-value and later collect them to Map
Pair I'm using here is from package org.springframework.data.util.Pair
public Mono<Map<String, String>> getFormData(MultiValueMap<String, Part> partMultiValueMap) {
Map<String, Part> multiPartMap = partMultiValueMap.toSingleValueMap();
return Flux.fromIterable(multiPartMap.entrySet())
.flatMap(entry -> {
Part part = entry.getValue();
if (part instanceof FormFieldPart) {
return Mono.just(
Pair.of(entry.getKey(), ((FormFieldPart) part).value()) // return Pair
);
} else {
return decodePartToString(part.content()) // decoding DataBuffers to string
.flatMap(decodedString ->
Mono.just(Pair.of(entry.getKey(), decodedString))); // return Pair
}
})
.collectMap(Pair::getFirst, Pair::getSecond); // map and collect pairs to Map<>
}
private Mono<String> decodePartToString(Flux<DataBuffer> dataBufferFlux) {
StringDecoder stringDecoder = StringDecoder.textPlainOnly();
return stringDecoder.decodeToMono(dataBufferFlux,
ResolvableType.NONE,
MimeTypeUtils.TEXT_PLAIN,
Collections.emptyMap()
);
}