Spring data Mongo db Convert from Document to Criteria

Question

So from a Criteria we have getCriteriaObject which returns Document and then you are able to do some operations on the document, but then I wanna use the results by converting back to a Criteria, I couldn't really find how.

Of course let's take in consideration complex Criteria with multiple operators etc. Any ideas?

Answer 1

Short answer: No

Criteria has Querydsl-Like syntax which allows the generation of type-safe queries. Reading from Document may introduce MongoDB incompatible commands or syntax for the current MongoDB version.

Long answer: Yes

We can implement walkaround with Java reflection to add Document key:value into Criteria private fields.
Warning: You assume your Document has compatible operators with correct syntax.

Add this helper method into your class (souce):

public static Criteria from(Document document) {
    Criteria c = new Criteria();

    try {

        Field _criteria = c.getClass().getDeclaredField("criteria");
        _criteria.setAccessible(true);

        @SuppressWarnings("unchecked")
        LinkedHashMap<String, Object> criteria = (LinkedHashMap<String, Object>) _criteria.get(c);

        for (Entry<String, Object> set : document.entrySet()) {
            criteria.put(set.getKey(), set.getValue());
        }

        Field _criteriaChain = c.getClass().getDeclaredField("criteriaChain");
        _criteriaChain.setAccessible(true);

        @SuppressWarnings("unchecked")
        List<Criteria> criteriaChain = (List<Criteria>) _criteriaChain.get(c);
        criteriaChain.add(c);

    } catch (Exception e) {
        // Ignore
    }

    return c;
}

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Now create new instance for Criteria from Document:

Criteria newCriteria = from(criteria.getCriteriaObject());

//You have full-compatible Criteria instance
newCriteria.and("foobar").elemMatch(Criteria.where("field").is("value"));