harmony 鸿蒙XML Generation

2023-10-30
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XML Generation

XML is a widely supported data exchange format used by various systems and applications. For example, web services often transmit structured data in XML format.

XML can also serve as a messaging format for communication between nodes in distributed systems.

Precautions

XML tags must always appear in pairs: one start tag and one end tag.
XML tags are case sensitive, meaning that the case of the start and end tags must match.

How to Develop

The XML module provides the XmlSerializer class to generate XML data. This class takes a fixed-length ArrayBuffer or DataView object as input, which is used to store the generated XML data.

You can call various methods to write different content. For example, call startElement(name: string) to write the start tag of an element and setText(text: string) to write the tag value.

For details about the APIs of the XML module, see @ohos.xml (XML Parsing and Generation). By calling the appropriate functions as needed, you can generate a complete XML document.

Import the module.

   import { xml, util } from '@kit.ArkTS';

Create a buffer and construct an XmlSerializer object, either based on an ArrayBuffer or a DataView object.

   // Method 1: Create an XmlSerializer object based on ArrayBuffer.
   let arrayBuffer: ArrayBuffer = new ArrayBuffer(2048); // Create a 2048-byte ArrayBuffer.
   let serializer: xml.XmlSerializer = new xml.XmlSerializer(arrayBuffer); // Create an XmlSerializer object based on the ArrayBuffer.

   // Method 2: Create an XmlSerializer object based on DataView.
   // let arrayBuffer: ArrayBuffer = new ArrayBuffer(2048); 
   // let dataView: DataView = new DataView(arrayBuffer); 
   // let serializer: xml.XmlSerializer = new xml.XmlSerializer(dataView);

Call the functions to generate XML data.

   serializer.setDeclaration(); // Write the XML declaration.
   serializer.startElement('bookstore'); // Write the start tag of an element.
   serializer.startElement('book'); // Write the start tag of a nested element.
   serializer.setAttributes('category', 'COOKING'); // Write attributes and attribute values.
   serializer.startElement('title');
   serializer.setAttributes('lang', 'en');
   serializer.setText('Everyday'); // Write the tag value.
   serializer.endElement(); // Write the end flag.
   serializer.startElement('author');
   serializer.setText('Giana');
   serializer.endElement();
   serializer.startElement('year');
   serializer.setText('2005');
   serializer.endElement();
   serializer.endElement();
   serializer.endElement();

Use Uint8Array to manipulate the ArrayBuffer, use TextDecoder to decode the Uint8Array, and output it.

   let uint8Array: Uint8Array = new Uint8Array(arrayBuffer); // Use Uint8Array to read data from the ArrayBuffer.
   let textDecoder: util.TextDecoder = util.TextDecoder.create(); // Call the TextDecoder class of the util module.
   let result: string = textDecoder.decodeToString(uint8Array); // Decode the Uint8Array.
   console.info(result);

The output is as follows:

   <?xml version="1.0" encoding="utf-8"?><bookstore>
     <book category="COOKING">
       <title lang="en">Everyday</title>
       <author>Giana</author>
       <year>2005</year>
     </book>
   </bookstore>