java - 如何将256个元素的数组检索到mongodb？

Question

我有一个像这样的集合数据格式，我现在传输 _id 和线路。如何返回256个元素的数组例如:传输_id:4行1045，返回行从(1045-256)到1045

{
  "_id" : 1,
  "fingerprint" : [ 
    {
        "line" : 1,
        "sub_finger" : "00000000"
    }, 
    {
        "line" : 2,
        "sub_finger" : "00000000"
    }, 
    {
        "line" : 3,
        "sub_finger" : "00000000"
    }, 
    {
        "line" : 4,
        "sub_finger" : "00000000"
    }, 
    {
        "line" : 5,
        "sub_finger" : "00000000"
    }, ...

Answer 1

您可以在 mongodb java 驱动程序中使用以下代码。

 MongoClient client = new MongoClient("localhost", 27017);
 MongoDatabase database = client.getDatabase("test");
 MongoCollection<Document> collection = database.getCollection("collection");
 Document result = collection.find(Filters.eq("_id", 4)).projection(Projections.slice("fingerprint", 1045-256, 256)).first()