Mongodb java driver query with binary _id

Question

I have a few entries in a mongodb database. They have binary _ids. If I query with a mongo client like robomongo I'm able to find the entry I'm looking for:

db.getCollection('comment').find({"_id" : new BinData(0,"nCgNlWhzJM9/lHDVQmXQrg==")})

However, I'm having serious issues with doing the same in java. Here is what I'm trying to do:

final MongoCollection<Document> mongoCollection = mongoDatabase.getCollection("comment");

mongoCollection
             .find(eq("_id", new Binary((byte) 0, "nCgNlWhzJM9/lHDVQmXQrg==".getBytes(StandardCharsets.UTF_8))))
             .first()

Sadly this is not working. Trying to find an item with a string type works (like eq("author", "someone) ).

David Hodgson · Accepted Answer · 2017-01-26 10:51:00Z

3

Your _id value nCgNlWhzJM9/lHDVQmXQrg== is shown Base64 encoded, so your java query should be written:

    Document doc = mongoCollection
    .find(eq("_id", new Binary((byte) 0, Base64.getDecoder().decode("nCgNlWhzJM9/lHDVQmXQrg=="))))
    .first();

To decode the key before using it to create the binary filter.

answered Jan 26, 2017 at 10:51

David Hodgson

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