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Working With XML in Scala

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  • Difficulty Level : Medium
  • Last Updated : 28 Mar, 2022
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Data scientists and machine learning engineers are often unaware that the majority of the data they get is often in CSV or, at times, JSON file format. However, this is a positive development since we must deal with vast amounts of data, and any format that makes it simple to read and interpret data should be highly valued. And those who deal with CSV data formats are well aware of the advantages of this data format.

Having said that, it is possible that this is not always the case. Unless you are working in entirely another language (for example, Python), you are most likely working in a Java environment. We are also more likely to receive data in an XML format than in any other format since XML has long been the standard for data transfer. As a result, we will need to extract the data from XML files and create data pipelines from the information we have gathered.

What exactly is XML?

With XML, which stands for Extensible Markup Language, it was intended that both computers and people would be able to grasp the content of the document. It goes without saying that the designers took inspiration from the very popular HTML. Perhaps you are correct in claiming that no one understands HTML and that we just see the final result delivered by the browsers. It’s possible that it was expected that XML would be viewed solely by developers, and as a result, it should have worked. Later on, however, we moved on to Service Oriented Architecture (SOA), where XML has emerged as the de-facto standard data format for inter-service communication. Here we’ll look at how to parse XML in Spark-Scala, which will be covered in the next article.

What is the purpose of XML?

When producing an XML document, We may tag data in a manner that is similar to how we tag data when constructing an HTML document. XML combines many of the great characteristics of HTML but was also created to solve some of the shortcomings of HTML. XML tags are really created by the user and stored in a schema, which may be either a document type definition (DTD) or a document written in the XML Schema programming language. In addition, namespaces may assist guarantee you have distinct tags for our XML document. The syntax of XML has more constraints than HTML, however, this results in quicker and cheaper surfing. The option to construct our own tagging system offers us the freedom to classify and arrange data for both conveniences of retrieval and ease of presentation. Data storage and retrieval, data transfer across diverse systems, data transformation, and information presentation are all currently possible with XML, which is already being used for publication. As it matures and becomes more capable, XML may enable single-source data retrieval and data presentation.

Working with XML in Scala :

Scala respects XML as though it were a first-class member of the community. In this case, rather than embedding XML documents into strings, We may insert them directly into our code, just as We would an int or double number.

For eg: We may generate a val called XML and applied example XML content to it. A new instance of scala.xml is created when it has been parsed. Elem. The Scala package scala.xml offers classes to generate XML documents, process them, read them, and save them.

Scala




scala> val xml = <greet>Hi</greet>
xml: scala.xml.Elem = <greet>Hi</greet>
  
scala> xml.getClass
res2: Class[_ <: scala.xml.Elem] = class scala.xml.Elem


Let’s have a look at how we can decipher it. XPath is a strong tool for querying the contents of an XML file. Scala includes a query capability that is similar to XPath, with a few minor differences. In XPath, we employ forward slashes “/” and “//” to query the XML documents. However, in Scala, the “/” symbol is used as a division operator, whereas the “//” symbol is used to remark code. When interacting with an XML document, Scala likes to utilize the reverse slashes “” and “.”

As an example,

Scala




scala> val xmlDoc =
322
244


We’d want to get our hands on the symbol components. We may use the XPath query to do this.

Scala




scala> val children = xmlDoc \ "symbol"
scala> children: scala.xml.NodeSeq = NodeSeq(322, 244)


We used the () function on the XML element and instructed it to search for any symbol elements. It returns a scala.xml object as an instance. NodeSeq is a collection of XML nodes that represents a collection of XML nodes.

It is just the elements that are immediate descendants of the target element that are searched for by the() function (i.e symbol). If we want to search across all of the items in the hierarchy beginning with the target element, we can use the _() function to do this.

Scala




val grandChildren = xmlDoc \\ "units"
grandChildren: scala.xml.NodeSeq = NodeSeq(100, 315)


And we may access text nodes contained inside an element by using the text function.


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