如何从 Java 中的 MongoDB 集合中检索特定字段的值

Question

I have a MongoDB database and I need to retrieve the list of values in a field. I have tried with:

     FindIterable<Document> findIterable = collection.find(eq("data", data)).projection(and(Projections.include("servizio"), Projections.excludeId()));
        ArrayList<Document> docs = new ArrayList();

        findIterable.into(docs);

        for (Document doc : docs) {
            nomeServizioAltro += doc.toString();
        }

but it prints

Document{{servizio=Antoniano}}Document{{servizio=Rapp}}Document{{servizio=Ree}}

While I want an array with these strings:

Antoniano,Rapp,Ree

Is there a way to do it?

Answer 1

You can try java 8 stream to output a list of servizio values.

List<String> res = docs.stream().
       map(doc-> doc.getString("servizio")).
       collect(Collectors.toList());

Using for loop

List<String> res = new ArrayList();
for(Document doc: docs) {
  res.add(doc.getString("servizio"));
}