从嵌套哈希图中检索值

发布于 2024-11-05 14:44:01 字数 2349 浏览 0 评论 0原文

我有一个包含许多表节点结构副本的 XML 文件，如下所示：

<databasetable TblID=”123” TblName=”Department1_mailbox”>
<SelectColumns>
    <Slno>dept1_slno</Slno>
    <To>dept1_to</To>
    <From>dept1_from</From>
    <Subject>dept1_sub</Subject>
    <Body>dept1_body</Body>
    <BCC>dept1_BCC</BCC>
    <CC>dept1_CC</CC>
</SelectColumns>
<WhereCondition>MailSentStatus=’New’</WhereCondition>
<UpdateSuccess>
    <MailSentStatus>’Yes’</MailSentStatus>
    <MailSentFailedReason>’Mail Sent Successfully’</MailSentFailedReason>
</UpdateSuccess>
<UpdateFailure>
    <MailSentStatus>’No’</MailSentStatus>
    <MailSentFailedReason>’Mail Sending Failed ’</MailSentFailedReason>
</ UpdateFailure>
</databasetable>

由于每次遍历文件以获取程序中查询的每个节点的详细信息并不是一种有效的方式，因此我使用了嵌套哈希图概念来首次遍历 XML 文件时存储详细信息。我使用的结构如下：

MapMaster
Key     Value
123     MapDetails
        Key         Value
        TblName         Department1_mailbox
        SelectColumns       mapSelect
                    Key         Value
                    Slno            dept1_slno
                    To          dept1_to
                    From            dept1_from
                    Subject         dept1_sub
                    Body            dept1_body
                    BCC         dept1_BCC
                    CC          dept1_CC
        WhereCondition      MailSentStatus=’New’
        UpdateSuccess       mapUS
                                    MailSentStatus      ’Yes’
                                    MailSentFailedReason    ’Mail Sent Successfully’
        UpdateFailure       mapUF
                                    MailSentStatus      ’No’
                                    MailSentFailedReason    ’Mail Sending Failed’

但我现在面临的问题是关于使用嵌套键检索值部分。例如，

如果我需要 Slno Key 的值，我必须以嵌套形式指定 TblID、SelectColumns、Slno，如下所示：

Stirng Slno = ((HashMap)((HashMap)mapMaster.get(“123”))mapDetails.get(“SelectColumns”))mapSelect.get(“Slno”);

这在程序中使用不方便。请提出一个解决方案，但不要告诉迭代器可用。因为我必须根据程序的需要从地图中获取单独的值。

编辑：我的程序必须获取有权发送邮件的部门的 ID，然后将这些 ID 与 XML 文件中的 ID 进行比较。仅从 XML 中获取这些 ID 的信息，相比之下返回 true。这就是我的全部计划。请帮忙。

提前致谢，维舒

原文

I have a XML file with many copies of table node structure as below:

<databasetable TblID=”123” TblName=”Department1_mailbox”>
<SelectColumns>
    <Slno>dept1_slno</Slno>
    <To>dept1_to</To>
    <From>dept1_from</From>
    <Subject>dept1_sub</Subject>
    <Body>dept1_body</Body>
    <BCC>dept1_BCC</BCC>
    <CC>dept1_CC</CC>
</SelectColumns>
<WhereCondition>MailSentStatus=’New’</WhereCondition>
<UpdateSuccess>
    <MailSentStatus>’Yes’</MailSentStatus>
    <MailSentFailedReason>’Mail Sent Successfully’</MailSentFailedReason>
</UpdateSuccess>
<UpdateFailure>
    <MailSentStatus>’No’</MailSentStatus>
    <MailSentFailedReason>’Mail Sending Failed ’</MailSentFailedReason>
</ UpdateFailure>
</databasetable>

As it is not an efficient manner to traverse the file for each time to fetch the details of each node for the queries in the program, I used the nested hashmap concept to store the details while traversing the XML file for the first time. The structure I used is as below:

MapMaster
Key     Value
123     MapDetails
        Key         Value
        TblName         Department1_mailbox
        SelectColumns       mapSelect
                    Key         Value
                    Slno            dept1_slno
                    To          dept1_to
                    From            dept1_from
                    Subject         dept1_sub
                    Body            dept1_body
                    BCC         dept1_BCC
                    CC          dept1_CC
        WhereCondition      MailSentStatus=’New’
        UpdateSuccess       mapUS
                                    MailSentStatus      ’Yes’
                                    MailSentFailedReason    ’Mail Sent Successfully’
        UpdateFailure       mapUF
                                    MailSentStatus      ’No’
                                    MailSentFailedReason    ’Mail Sending Failed’

But the problem I’m facing now is regarding retrieving the Value part using the nested Keys. For example,

If I need the value of Slno Key, I have to specify TblID, SelectColumns, Slno in nested form like:

Stirng Slno = ((HashMap)((HashMap)mapMaster.get(“123”))mapDetails.get(“SelectColumns”))mapSelect.get(“Slno”);

This is unconvinent to use in a program. Please suggest a solution but don’t tell that iterators are available. As I’ve to fetch the individual value from the map according to the need of my program.

EDIT:my program has to fetch the IDs of the department for which there is privilege to send mails and then these IDs are compared with the IDs in XML file. Only information of those IDs are fetched from XML which returned true in comparison. This is all my program. Please help.

Thanks in advance,
Vishu

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橘香 2024-11-12 14:44:01

永远不要转换为特定的 Map 实现。最好使用转换为 Map 接口，即
((Map)one.get("foo")).get("bar")
不要在您的情况下使用强制转换。您可以使用泛型定义集合，因此编译器将为您工作：
地图<字符串，地图> one = new HashMap();
Map<字符串、整数> Two = new HashMap();

现在你可以说：

int n = one.get("foo").get("bar");

没有转换，没有问题。

但更好的解决方案是根本不使用嵌套表。创建自定义类，例如 SelectColumns、WhereCondition 等。每个类都应该有适当的私有字段、getter 和 setter。现在解析您的 XML 创建这些类的实例。然后使用getter来遍历数据结构。

顺便说一句，如果您想使用 JAXB，您几乎不需要做任何事情！像下面这样：

Unmarshaller u = JAXBContext.newInstance(SelectColumns.class, WhereCondition.class).createUnmarshaller();
SelectColumns[] columns = (SelectColumns[])u.unmarshal(in);

Never cast to specific Map implementation. Better use casting to Map interface, i.e.
((Map)one.get("foo")).get("bar")
Do not use casting in your case. You can define collection using generics, so compiler will do work for you:
Map<String, Map> one = new HashMap<String, Map>();
Map<String, Integer> two = new HashMap<String, Integer>();

Now your can say:

int n = one.get("foo").get("bar");

No casting, no problems.

But the better solution is not to use nested tables at all. Create your custom classes like SelectColumns, WhereCondition etc. Each class should have appropriate private fields, getters and setters. Now parse your XML creating instance of these classes. And then use getters to traverse the data structure.

BTW if you wish to use JAXB you do not have to do almost anything! Something like the following:

Unmarshaller u = JAXBContext.newInstance(SelectColumns.class, WhereCondition.class).createUnmarshaller();
SelectColumns[] columns = (SelectColumns[])u.unmarshal(in);

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