@Override
    public Object decode(@NonNull DataBuffer dataBuffer,
                         @NonNull ResolvableType targetType,
                         MimeType mimeType,
                         Map<String, Object> hints) throws DecodingException {
        try (ByteArrayOutputStream os = new ByteArrayOutputStream();
                InputStream in = dataBuffer.asInputStream()) {
            byte[] buf = new byte[1 << 16];
            for (; ; ) {
                int len = in.read(buf);
                if (len == -1) {
                    break;
                }
                if (len > 0) {
                    os.write(buf, 0, len);
                }
            }
            Object value = JSON.parseObject(os.toByteArray(),
                    targetType.getType(),
                    this.config.getDateFormat(),
                    this.config.getReaderFilters(),
                    this.config.getReaderFeatures());
            logValue(value, hints);
            return value;
        } catch (JSONException ex) {
            throw new DecodingException("JSON parse error: " + ex.getMessage(), ex);
        } catch (IOException ex) {
            throw new DecodingException("I/O error while reading input message", ex);
        } finally {
            DataBufferUtils.release(dataBuffer);
        }
    }
Fastjson2 for Spring WebFlux.

@author Xi.Liu
@see AbstractJackson2Decoder
extension-spring6/src/main/java/com/alibaba/fastjson2/support/spring6/http/codec/Fastjson2Decoder.java