# 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)](../reference/apis-arkts/js-apis-xml.md). By calling the appropriate functions as needed, you can generate a complete XML document.

1. Import the module.

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

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

   ```ts
   // 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);
   ```

3. Call the functions to generate XML data.

   ```ts
   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();
   ```

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

   ```ts
   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>
   ```