How to check Blob objects for equality?

Question

Rather disappointingly for Blobs this assertion fails:

System.assert(Blob.valueOf('abc') == Blob.valueOf('abc'));

though the Apex Expression Operators documentation over ambitiously says that:

Unlike Java, == in Apex compares object value equality, not reference equality, except for user-defined types.

So it seems that to test equality where the blobs have the same size requires the blobs to be put through EncodingUtil.base64Encode which may lead to heap limit problems e.g.:

private static Boolean eq(Blob b1, Blob b2) {
    if (b1.size() == b2.size()) {
        String s1 = EncodingUtil.base64Encode(b1);
        String s2 = EncodingUtil.base64Encode(b2);
        return s1 == s2;
    } else {
        return false;
    }
}

I there a better way to go?

Answer 1

The equals operator == does work as expected with Blob, so there's no reason to jump through extra hoops, such as your eq method. However, one possibility is that you may have had a different case in your code; since Blobs are binary data, they are case-sensitive in respect to equality:

Blob a = blob.valueof('hello world'),
    b = blob.valueof('Hello world');
system.assertequals(a, b); // Assertion fails

This is in contrast to normal String comparison, which is case-insensitive.