gcsfileupload.java

    public void upload() {
        byte[] buffer = new byte[4096];

        BlobInfo build = BlobInfo.newBuilder("some-bucket", "samplefile1.txt").build();
        Field uploadIdField = BaseWriteChannel.class.getDeclaredField("uploadId");
        ReflectionUtils.makeAccessible(uploadIdField);

        try (WriteChannel writer = storage.writer(build)) {
            String uploadId = (String) ReflectionUtils.getField(uploadIdField, writer);
            String changedHostUploadId = changeHost(uploadId, "myinternalhost.test.com");
            ReflectionUtils.setField(uploadIdField, writer, changedHostUploadId);

            try (InputStream input = this.getClass().getResourceAsStream("/samplefile.txt")) {
                int limit;
                while ((limit = input.read(buffer)) >= 0) {
                    writer.write(ByteBuffer.wrap(buffer, 0, limit));
                }
            }
        }
    }
    
    private String changeHost(String uploadId, String newAuthority) {
        URI uri = URI.create(uploadId);
        try {
            URI newUri = new URI(uri.getScheme(), newAuthority, uri.getPath(), uri.getQuery(), uri.getFragment());
            return newUri.toString();
        } catch (URISyntaxException e) {
            throw new RuntimeException(e);
        }
    }