Java - MongoDB 不区分大小写，不检查完全匹配

Question

I'm trying to have case insensitive queries but by doing this, it's possible to find users by inputting parts of their username. ie a username types in "f" and there is a user with the username "foo" it will return foo's document.

I'm using this to check for case insensitive matches

private DBObject getQuery(String where, String whereValue)
{
    return new BasicDBObject(where, Pattern.compile(whereValue, Pattern.CASE_INSENSITIVE));
}

How can I check for exact matches but ignore case?

Answer 1

This is really all about your regex pattern you are using. For "foo" and only "foo" anywhere in the string, use this:

/\bfoo\b/i

Or specifically at the "start" of the string:

/^foo\b/i

Without the specifics you will not get a "specific" match.

MongoDB uses the pcre library ( or at least compatible ) so use expressions that match that constraint.

Of course that does include the "i" option for case insensitive as you asked. So this will match the "words" for "foo" and "FOO" as well as other possible case variations.

Also note, that when using MongoDB regex based queries, unless the string is "anchored" with the caret "^" to the start of the string, then the search is done over all documents in the collection, and not just only those that contain "foo" in some form somewhere.

Only the caret "^" can make use of an index, but then again the "case insensitive" option also blows this away.

For efficient searches, include a string in your document with "normalized" case, and hopefully be looking from the beginning of the string only.

Answer 2

Start your regular expression with ^ character and end with $ character and it will works fine.

private DBObject getQuery(String where, String whereValue)
{
    return new BasicDBObject("^" + where + "$", Pattern.compile(whereValue, Pattern.CASE_INSENSITIVE));
}

Answer 3

In given above answer one thing is mistaken. regex is applied on key rather than value. to rectify it we should apply regex on value rather than regex like code given below.

private DBObject getQuery(String where, String whereValue)
{
return new BasicDBObject(where, Pattern.compile("^" + whereValue + "$", Pattern.CASE_INSENSITIVE));
}

Now it will correctly make case insensitive search. Enjoy Dear :)