I’m working on a Java project that integrates with Google Documents API version 3.0. I’m having trouble with MD5 checksum handling when uploading files.
Here’s my current implementation:
DocumentEntry docEntry = new DocumentEntry();
docEntry.setFileContent(uploadFile, FileUtils.detectContentType(uploadFile));
docEntry.setFileName(documentName.getPlainText());
docEntry.setDocumentTitle(documentName);
docEntry.setDraftMode(false);
docEntry.setVisibility(!uploadFile.isHidden());
docEntry.setMd5Checksum(FileUtils.calculateMD5Hash(uploadFile));
The FileUtils.calculateMD5Hash(uploadFile) method definitely produces a correct MD5 hash in hexadecimal format. I’ve verified this multiple times.
The upload process works fine and the file appears in Google Docs. However, when I fetch the document later and call docEntry.getMd5Checksum(), it consistently returns null instead of the checksum I set.
I’ve also attempted setting other properties like ETag, ResourceID, and VersionID manually, but the API seems to ignore these values and either sets them to null or generates its own values.
Why isn’t the MD5 checksum being preserved during upload?
Google Docs API v3.0 doesn’t preserve the MD5 checksums you provide. When you upload a file, the checksum is used merely for verification that the upload was successful. After that, the API generates its own checksum based on how the document is processed and stored. This is particularly true for Google Docs files, where even minor metadata adjustments can alter the binary content leading to a different checksum. I faced a similar issue with a document management system and resolved it by creating a mapping table in my database to maintain the original file checksums, rather than relying on the API to retain them. This allowed for validation of files post-upload.
This is actually how Google Docs API v3.0 works. The MD5 checksum you upload is just for verifying the transfer went okay - Google doesn’t keep it. They recalculate checksums based on how they store the document internally after processing it. I hit this same issue building a backup system for our company docs. What worked was keeping the original checksums in our own database before uploading, then using Google’s revision API to track changes instead of comparing MD5s. For checking if documents changed, use the revision timestamp and file size instead. They’re way more reliable than checksums in Google’s system.
Yeah, hit the same issue migrating old docs. Google dumps your MD5 right after upload verification and creates their own during internal processing. They recalculate the checksum when converting/storing the file. I store original hashes separately now and use ETags for change detection - way more reliable than matching checksums.