@Override public CompletableFuture<List<FileProvenanceElement>> getHistory(String processIdentifier, String fileId) { CompletableFuture<AuthorizationInfo> authorizationTree = this.blockchain.getAuthorizationTree(processIdentifier); return this.blockchain .getProvenance(processIdentifier) .thenCombine(authorizationTree, (provenanceElements, authorizationInfo) -> { List<FileProvenanceElement> result; if (authorizationInfo != null) { result = getHistoryOfSingleFile(provenanceElements, fileId, authorizationInfo); } else { LOGGER.info(NO_AUTHORIZATION_DATA); FileProvenanceElement historyElement = new FileProvenanceElement("", 0, NO_AUTHORIZATION_DATA); historyElement.setAuthorized(false); historyElement.setFileName(fileId); result = Collections.singletonList(historyElement); } return result; }); }