Java Mongodb regex query

Question

I have to run this query in Java

 db.Users.find({"name": /^ind/i})

My Java code is

Document findQuery = new Document();
findQuery.append("name", Pattern.compile("/^"+name+"/i"));
FindIterable<Document> iterable = db.getCollection("Users").find(findQuery);

It is not returning any data, I think the above java code is converting

> /^ind/i into "/^ind/i"

Thanks in advance.

Edit:

Based on stribizhev suggestion updated the query and its worked

db.Users.find({"name": {"$regex": /^ind/, "$options": "i"}})

Java code

Document regQuery = new Document();
regQuery.append("$regex", "^(?)" + Pattern.quote(name));
regQuery.append("$options", "i");

Document findQuery = new Document();
findQuery.append("name", regQuery);
FindIterable<Document> iterable = db.getCollection("Users").find(findQuery);

Answer 1

You cannot use regex delimiters in Java Pattern.compile, as there are other means in Java (e.g. flags) to do the same.

To enforce case-insensitive search, use inline modifier (?i). So, use "^(?i)"+Pattern.quote(name) instead of "/^"+name+"/i".

Pattern.quote just escapes all regex metacharacters so that they were treated as literals (same as \Q...\E).

Answer 2

I guess there is a more elegant way to do that in Java, by using the provided Filters in the MongoDB Java Driver (version 3 and above):

Document query = new Document("equipment","gloves");

//whatever pattern you need. But you do not need the "/" delimiters
String pattern = ".*" + query.getString("equipment") + ".*";

//find(regex("field name", "pattern", "options"));
collection.find(regex("equipment", pattern, "i"));

Answer 3

You could use Pattern -and Filters-

Pattern regex = Pattern.compile("ind", Pattern.CASE_INSENSITIVE);
Bson filter = Filters.eq("name", regex);

The object Pattern has some other flags, as you can see here