This is really not as complicated as other answers imply.
The only way to stream the data without buffering it all in memory is to use a pipe, as @jin-kwon suggested. However, it can be done very simply by using Spring's BodyExtractors and DataBufferUtils utility classes.
Example:
private InputStream readAsInputStream(String url) throws IOException {
PipedOutputStream osPipe = new PipedOutputStream();
PipedInputStream isPipe = new PipedInputStream(osPipe);
ClientResponse response = webClient.get().uri(url)
.accept(MediaType.APPLICATION.XML)
.exchange()
.block();
final int statusCode = response.rawStatusCode();
// check HTTP status code, can throw exception if needed
// ....
Flux<DataBuffer> body = response.body(BodyExtractors.toDataBuffers())
.doOnError(t -> {
log.error("Error reading body.", t);
// close pipe to force InputStream to error,
// otherwise the returned InputStream will hang forever if an error occurs
try(isPipe) {
//no-op
} catch (IOException ioe) {
log.error("Error closing streams", ioe);
}
})
.doFinally(s -> {
try(osPipe) {
//no-op
} catch (IOException ioe) {
log.error("Error closing streams", ioe);
}
});
DataBufferUtils.write(body, osPipe)
.subscribe(DataBufferUtils.releaseConsumer());
return isPipe;
}
If you don't care about checking the response code or throwing an exception for a failure status code, you can skip the block()
call and intermediate ClientResponse
variable by using
flatMap(r -> r.body(BodyExtractors.toDataBuffers()))
instead.
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