I am trying to create a zip file and upload that zip file in AWS S3 via a multipart upload route. However, I am facing an issue where the file is successfully getting generated however, the contents inside the files are getting corrupted.

Here is the error that I am getting when I am trying to unarchive the file :

Archive:  test2MB.zip
  End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
unzip:  cannot find zipfile directory in one of test2MB.zip or
        test2MB.zip.zip, and cannot find test2MB.zip.ZIP, period.

Here are the code snippets that I have written for this

private Single<List<CompletedPart>> zipAndUploadZipParts(String uploadId) {
        List<Single<CompletedPart>> uploadPartObservables = new ArrayList<>();
        final int[] partNumber = {Constants.START_PART_NUMBER};

        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        ZipOutputStream zipOutputStream = new ZipOutputStream(byteArrayOutputStream);
        return zipMetadata(zipOutputStream)
                .andThen(uploadZipPart(byteArrayOutputStream, uploadPartObservables, partNumber, uploadId)
                        .onErrorResumeNext(error -> {
                            this.contextRx.log().error(String.format("placeholder", partNumber[0], this.logIdentifier, error.getMessage()), error);
                            return Completable.error(new RuntimeException("Placeholder"));
                        }))
                .andThen(finalizeZipUpload(uploadPartObservables, zipOutputStream, byteArrayOutputStream));
    }

    private Completable zipMetadata(ZipOutputStream zipOutputStream) {
        return Completable.create(emitter -> {
            try {
                ZipEntry metadataEntry = new ZipEntry(Constants.METADATA_FILE_NAME);
                zipOutputStream.putNextEntry(metadataEntry);
                zipOutputStream.write(this.catalogObjectsMetadata.getBytes());
                zipOutputStream.closeEntry();
                emitter.onComplete();
            } catch (IOException exception) {
                this.contextRx.log().error(String.format(Constants.LOG_ERROR_ZIPPING_METADATA, this.logIdentifier, exception.getMessage()), exception);
                emitter.onError(new RuntimeException(String.format(Constants.ERROR_ZIPPING_METADATA)));
            }
        });
    }

    private Completable uploadZipPart(ByteArrayOutputStream byteArrayOutputStream, List<Single<CompletedPart>> uploadPartObservables, int[] partNumber, String uploadId) {
        return Completable.create(emitter -> {
            try {
                byte[] zipData = byteArrayOutputStream.toByteArray();
                uploadPartObservables.add(uploadPart(zipData, partNumber[0]++, uploadId));
                byteArrayOutputStream.reset();
                this.contextRx.log().info(String.format("Uploaded part %d for uploadId %s", partNumber[0] - 1, uploadId));
                emitter.onComplete();
            } catch (Exception exception) {
                emitter.onError(exception);
            }
        });
    }

private Single<List<CompletedPart>> finalizeZipUpload(List<Single<CompletedPart>> uploadPartObservables, ZipOutputStream zipOutputStream, ByteArrayOutputStream byteArrayOutputStream) {
        return Single.defer(() -> {
            try {
                zipOutputStream.finish();
            } catch (IOException e) {
                return Single.error(new RuntimeException("Error finishing zip output stream", e));
            } finally {
                try {
                    zipOutputStream.close();
                } catch (IOException e) {
                    return Single.error(new RuntimeException("Error closing zip output stream", e));
                }
                try {
                    byteArrayOutputStream.close();
                } catch (IOException e) {
                    return Single.error(new RuntimeException("Error closing byte array output stream", e));
                }
            }
            return Single.merge(uploadPartObservables)
                    .toList()
                    .doOnSuccess(parts -> this.contextRx.log().info(String.format(Constants.ALL_PARTS_UPLOADED, this.logIdentifier, parts)))
                    .onErrorReturnItem(new ArrayList<>());
        });
    }

Can someone guide what is wrong with my code which is corrupting my zip file?

Contents inside the zip file shouldn’t get corrupted.