Android XML Adventure – Create & Write XML Data

Article Series: Android XML Adventure

Author: Pete Houston (aka. `xjaphx`)

TABLE OF CONTENTS

1. What is the “Thing” called XML?
2. Parsing XML Data w/ SAXParser
3. Parsing XML Data w/ DOMParser
4. Parsing XML Data w/ XMLPullParser
5. Create & Write XML Data
6. Compare: XML Parsers
   
7. Parsing XML using XPath
   
8. Parsing HTML using HtmlCleaner
9. Parsing HTML using JSoup
10. Sample Project 1: RSS Parser – using SAXParser
11. Sample Project 1: RSS Parser – using DOM Parser
12. Sample Project 1: RSS Parser – using XMLPullParser
13. Sample Project 2: HTML Parser – using HtmlCleaner
14. Sample Project 2: HTML Parser – using JSoup
15. Finalization on the “Thing” called XML!

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Have you mastered with parsing XML stuffs well?

Today, I’d like to talk about writing XML file, just like a normal Java program, there’s no differences.

Our steps are going to be:

+ First, create XML string (which is residing in memory for later use).

+ Second, write the XML string to a file, which belongs to internal storage of an Android application.

About the second step, I assume that you’ve already known how to do it. Shortly, `Context.openFileOutput()` will do the job.

For the first thing, there various ways to do; however, I’d like to introduce only most three common ways.

1. A normal String format

Understand what I mean?

	public static String writeUsingNormalOperation(Study study) {
		String format =
				"<?xml version='1.0' encoding='UTF-8'?>" +
				"<record>" +
				"	<study id='%d'>" +
				"		<topic>%s</topic>" +
				"		<content>%s</content>" +
				"		<author>%s</author>" +
				"		<date>%s</date>" +
				"	</study>" +
				"</record>";
		return String.format(format, study.mId, study.mTopic, study.mContent, study.mAuthor, study.mDate);
	}

The Good:

• Very quick and easy.
• Not much code or custom objects required.

The Bad:

• Straightforwardly static string, if you want to output a list of XML tags, this way doesn’t work.
• Easy to make mistake while making the format for output.

2. Using DOM

	public static String writeUsingDOM(Study study) throws Exception {
		Document doc = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
		// create root: <record>
		Element root = doc.createElement(Study.RECORD);
		doc.appendChild(root);

		// create: <study>
		Element tagStudy = doc.createElement(Study.STUDY);
		root.appendChild(tagStudy);
		// add attr: id =
		tagStudy.setAttribute(Study.ID, String.valueOf(study.mId));

		// create: <topic>
		Element tagTopic = doc.createElement(Study.TOPIC);
		tagStudy.appendChild(tagTopic);
		tagTopic.setTextContent(study.mTopic);

		// create: <content>
		Element tagContent = doc.createElement(Study.CONTENT);
		tagStudy.appendChild(tagContent);
		tagContent.setTextContent(study.mContent);

		// create: <author>
		Element tagAuthor = doc.createElement(Study.AUTHOR);
		tagStudy.appendChild(tagAuthor);
		tagAuthor.setTextContent(study.mAuthor);

		// create: <date>
		Element tagDate = doc.createElement(Study.DATE);
		tagStudy.appendChild(tagDate);
		tagDate.setTextContent(study.mDate);

		// create Transformer object
		Transformer transformer = TransformerFactory.newInstance().newTransformer();
		StringWriter writer = new StringWriter();
		StreamResult result = new StreamResult(writer);
		transformer.transform(new DOMSource(doc), result);

		// return XML string
		return writer.toString();
	}

The Good:

• Implementable for dynamic data output.
• Flexible XML configuration.

The Bad:

• Too much object creations, using a lot.
• Performance gets worse if XML document is large.

3. Using XMLSerializer

	public static String writeUsingXMLSerializer(Study study) throws Exception {
		XmlSerializer xmlSerializer = Xml.newSerializer();
		StringWriter writer = new StringWriter();

		xmlSerializer.setOutput(writer);
		// start DOCUMENT
		xmlSerializer.startDocument("UTF-8", true);
		// open tag: <record>
		xmlSerializer.startTag("", Study.RECORD);
		// open tag: <study>
		xmlSerializer.startTag("", Study.STUDY);
		xmlSerializer.attribute("", Study.ID, String.valueOf(study.mId));

		// open tag: <topic>
		xmlSerializer.startTag("", Study.TOPIC);
		xmlSerializer.text(study.mTopic);
		// close tag: </topic>
		xmlSerializer.endTag("", Study.TOPIC);

		// open tag: <content>
		xmlSerializer.startTag("", Study.CONTENT);
		xmlSerializer.text(study.mContent);
		// close tag: </content>
		xmlSerializer.endTag("", Study.CONTENT);

		// open tag: <author>
		xmlSerializer.startTag("", Study.AUTHOR);
		xmlSerializer.text(study.mAuthor);
		// close tag: </author>
		xmlSerializer.endTag("", Study.AUTHOR);

		// open tag: <date>
		xmlSerializer.startTag("", Study.DATE);
		xmlSerializer.text(study.mDate);
		// close tag: </date>
		xmlSerializer.endTag("", Study.DATE);

		// close tag: </study>
		xmlSerializer.endTag("", Study.STUDY);
		// close tag: </record>
		xmlSerializer.endTag("", Study.RECORD);

		// end DOCUMENT
		xmlSerializer.endDocument();

		return writer.toString();
	}

The Good:

• Not like DOM, it requires only at least two objects to create XML document.
• The syntax is so damn easy to work with.
• The performance is pretty good.

The Bad:

• At this point, I’ve not faced any drawback of using this.

4. Simple Framework

Homepage: http://simple.sourceforge.net/

This is an amazing XML Serialization/De-serialization, it is really easy to use and having quite good performance on XML data structure.

However, I’m not going to talk about it here, so you might want to discover about it yourselves. Or maybe, I will give a quick look over this framework in another article.

Well, it’s end for today post, and happy learning!

Be await for the next article on the series.

Cheers,

Pete Houston