Reverse Regex Selection with Spring MongoDB

Question

I have a mongo collection with objects like these:

[
{
    "_id" : "a2d",
    "entityType" : "Location",
    "type" : "STRING",
},
{
    "_id" : "a1_order",
    "entityType" : "Order",
    "type" : "STRING",
}
]

Trying to append the _entityType to all document's id where it is not present at the end id the id (the first object in the above case).

Using mongo with Spring, but I'm already stuck with the first step, to get all the objects with no entityType in id.

Thinking about something like this, with regex, but I'm not sure how should it look like:

Query query = new Query();
query.addCriteria( Criteria.where( "id" ).regex( "here i need the entity type of the current document" ) );

TheLastOne · Accepted Answer · 2017-07-04 10:08:11Z

2

You can build your regex by '^' ('starts with' Regex).

So you need a function who point in all documents and check this filter

    List<Document> result = new ArrayList<Document>();
    StringBuilder idPrefix = new StringBuilder();
    idPrefix.append("^");
    idPrefix.append(idCode);
    idPrefix.append("_");
    List<Bson> filters = new ArrayList<Bson>();
    filters.add(Filters.regex("_id", keyPrefix.toString()));
    for (Document d : yourCollections.find(Filters.and(filters)))
        list.add(d);

answered Jul 4, 2017 at 10:08

TheLastOne

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Comments

Neil Lunn · Accepted Answer · 2017-07-04 08:53:57Z

You actually want a "reverse regex" here, as you need to use the data in the document in order to match on another field.

Presently you can really only do this with MongoDB using $where, which evaluates JavaScript on the server. So for spring mongo, you need the BasicQuery instead, so we can construct from BasicDBObject and Code primatives:

    BasicDBObject basicDBObject = new BasicDBObject("$where",
            new Code("!RegExp('_' + this.entityType + '$','i').test(this.id)"));

    BasicQuery query = new BasicQuery(basicDBObject);

That will test the "id" field in the document to see if it matches the value from entityType at the "end of the string" and without considering "case". The ! is a Not condition, so the "reverse" of the logic is applied to "not match" where the field actually did end that way.

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