爲什麼mongoTemplate返回數字類型（int）的列值是雙倍的？

Question

我想從以下文檔中獲取uniq account_numbers。

{ 
    "_id" : ObjectId("5825e49785a4caf2bfa64a2f"), 
    "profit" : "", 
    "account_number" : 10, 
    "m_number" : "", 
    "registration_number" : "", 
    "page_number" : "", 
    "entry_date" : ISODate("2016-04-01T07:35:35Z"), 
    "narration" : "By cash", 
    "voucher_number" : "", 
    "debit_credit" : 6150, 
    "account_code" : 2102, 
    "created_at" : ISODate("2016-04-01T07:35:35Z"), 
    "updated_at" : ISODate("2016-04-01T07:35:35Z"), 
    "employee_id" : 0, 
    "balance" : 0, 
    "credit" : 0, 
    "debit" : 0, 
    "particulars" : "", 
    "since_last" : 0, 
    "transaction_type" : 0, 
    "voucher_path" : "", 
    "branch" : "", 
    "auto_voucher_number" : "", 
    "check_book_series" : "" 
} 

account_number類型是數字，我想要使用Spring Mongo模板以int形式獲取它。

Query query = new Query(); 
    query.addCriteria(Criteria.where("account_code").is(accountCode).and("account_number").exists(true)); 
    return List accounts = mongoTemplate.getCollection("transaction").distinct("account_number", query.getQueryObject()); 

上面的代碼是返回列表帳戶。查看調試結果

accounts = {ArrayList@6192} size = 2815 
0 = {Double@6217} "1626.0" 
1 = {Double@6218} "1670.0" 
2 = {Double@6219} "2936.0" 
3 = {Double@6220} "2295.0" 
4 = {Double@6221} "1010.0" 
5 = {Double@6222} "1471.0" 
6 = {Double@6223} "3333.0" 
7 = {Double@6224} "1469.0" 
8 = {Double@6225} "3445.0" 
9 = {Double@6226} "3193.0" 
10 = {Double@6227} "219.0" 
11 = {Double@6228} "2509.0" 
12 = {Double@6229} "3750.0" 
13 = {Double@6230} "3425.0" 

簡短的問題是 - 如何從文檔中獲取int類型列表以及爲什麼返回雙類型？

這裏是文檔的POJO，可能是我需要在現場定義的東西？

@Document(collection = "transaction") 
public class Transaction implements Serializable { 

    private static final Long serialVersionUID = 1L; 

    @Id 
    //@GeneratedValue(strategy = GenerationType.IDENTITY) 
    @Field(value = "id") 
    private String id; 

    @Field(value = "account_code") 
    private Integer accountCode; 

    @Field(value = "account_number") 
    private Integer accountNumber; 

Answer 1

默認情況下，MongoDB中保存數值雙打：

對於db.coll.save({x: 1})：x將被表示（和你的Java驅動程序轉換）爲1.0雙。

要插入一個32位整數，你必須做到：

db.coll.save({x: NumberInt(1)})

和64個整數，這樣做：

db.coll.save({x: NumberLong(1)})

底層Java驅動程序也將1保存爲雙（我認爲）通過DBObject或Document。

如果你在你的代碼仔細看看：

mongoTemplate.getCollection("transaction") ...

這裏你落回DBCollection它返回account_number這是一個原始名單，是說，表示爲默認雙。 MongoTemplate映射和轉換在這裏沒有關係：它們用於整個文檔（例如find方法），這裏不是這種情況。

爲了在這裏使用int，你將不得不自己轉換爲List值，或改變account_number存儲值NumberInt。