As you're using Spring Data, you could use a Query object to query all documents in the colletion and sort the results.
MongoOperations mongoOperations = mongoConfiguration.getMongoTemplate();
Query q = new Query().with(new Sort(Sort.Direction.ASC, "_id"));
List<Resource> resourceList = mongoOperations.find(q, Resource.class);
return resourceList;
Of course that you could iterate the list of results and sort it manually, or even use Collection.sort method, but I think if you have an index in the property that you're using to sort, it's faster to mongodb sort the results.