java查询大量Mongo数据

public void cursorFind(){
        Bson query=new BasicDBObject();
//        Bson query1 = Filters.in("_id",digests);
        MongoCursor<Document> cursor = null;
        int count=0;
        try{
            FindIterable<Document> findIterable=mongoTemplate.getCollection("yldc-v2-payload").find(query);
            cursor = findIterable.iterator();
            while (cursor.hasNext()) {
                Map obj=cursor.next();
                mongoTemplate.save(obj,"env-v2-payload.bak");
                log.info("saving...:{}",count++);
            }
        }catch(Exception e){
            System.out.println("error");
        }
    }