为什么mongoTemplate返回的数字类型(int)列值是双精度的?

我试图从以下文档中获取uniq account_Number。

{
    "_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类型是number,我希望使用Spring Mongo模板将其获取为int。

 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());

上面的代码正在返回列表帐户。查看调试结果

 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"

简短的问题是-如何从文档中获取int类型列表,以及为什么返回双类型?

这是文档的POJO,我是否需要在字段中定义一些内容?

@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;