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 parsing of xml sax process
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XML Parsing:

  • A parser is a piece of program that takes a physical representation of some data and converts it into an in-memory form for the program as a whole to use.
  • Parsers are used everywhere in software.
  • An XML parser is a software library or package that provides interfaces for client applications to work with an XML document.
  • An XML Parser is a parser that is designed to read XML and create a way for programs to use XML.
 flow diagram of xml parser flow diagram of xml sax parser
android xml parser sample code

Types of XML Parsers

  • These are the two main types of XML Parsers:
    • DOM
    • SAX

1. DOM (Document Object Model)

  • A DOM document is an object which contains all the information of an XML document. It is composed like a tree structure. The DOM Parser implements a DOM API. This API is very simple to use.

2. SAX (Simple API for XML)

  • SAX (Simple API for XML) is an event-driven online algorithm for parsing XML documents, with an API developed by the XML-DEV mailing list.
  • SAX provides a mechanism for reading data from an XML document that is an alternative to that provided by the Document Object Model (DOM).
  • The SAX parser cannot be used to create the XML file, It can be used to parse the xml file only.

Advantage of SAX Parser over DOM:

  • It consumes less memory than DOM.

Disadvantages of SAX:

  • We have no random access to an XML document since it is processed in a forward-only manner
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Example of android SAX Xml parsing

activity_main.xml

  • Drag the one textview from the pallete.
  • Now the activity_main.xml file will look like this:
  • File: activity_main.xml
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<RelativeLayout xmlns:androclass="http://schemas.android.com/apk/res/android"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    tools:context=".MainActivity" >  
  
    <TextView  
        android:id="@+id/textView1"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignParentLeft="true"  
        android:layout_alignParentTop="true"  
        android:layout_marginLeft="75dp"  
        android:layout_marginTop="46dp"  
        android:text="TextView" />  
  
</RelativeLayout> 
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xml document

  • Create an xml file named file.xml inside the assets directory of your project.
  • File: file.xml
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<?xml version="1.0"?>  
<records>  
<employee>  
<name>Sachin Kumar</name>  
<salary>50000</salary>  
</employee>  
<employee>  
<name>Rahul Kumar</name>  
<salary>60000</salary>  
</employee>  
<employee>  
<name>John Mike</name>  
<salary>70000</salary>  
</employee>  
</records>  
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Activity class

  • Now write the code to parse the xml using sax parser.
  • File: MainActivity.java
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package com.wikitechy.saxxmlparsing;  
import java.io.InputStream;  
import javax.xml.parsers.SAXParser;  
import javax.xml.parsers.SAXParserFactory;  
import org.xml.sax.Attributes;  
import org.xml.sax.SAXException;  
import org.xml.sax.helpers.DefaultHandler;  
import android.app.Activity;  
import android.os.Bundle;  
import android.widget.TextView;  
public class MainActivity extends Activity {  
TextView tv;  
@Override  
  
public void onCreate(Bundle savedInstanceState) {  
super.onCreate(savedInstanceState);  
setContentView(R.layout.activity_main);  
tv=(TextView)findViewById(R.id.textView1);  
try {  
SAXParserFactory factory = SAXParserFactory.newInstance();  
  
SAXParser saxParser = factory.newSAXParser();  
  
  
DefaultHandler handler = new DefaultHandler() {  
  
boolean name = false;  
  
boolean salary = false;  
  
  
public void startElement(String uri, String localName,String qName,  
Attributes attributes) throws SAXException {  
if (qName.equalsIgnoreCase("name"))  
{  
name = true;  
}  
if (qName.equalsIgnoreCase("salary"))  
{  
salary = true;  
}  
}//end of startElement method  
public void endElement(String uri, String localName,  
String qName) throws SAXException {  
}  
  
public void characters(char ch[], int start, int length) throws SAXException {  
if (name) {  
  
tv.setText(tv.getText()+"\n\n Name : " + new String(ch, start, length));  
name = false;  
}  
if (salary) {  
tv.setText(tv.getText()+"\n Salary : " + new String(ch, start, length));  
salary = false;  
}  
}//end of characters  
 method  
};//end of DefaultHandler object  
  
InputStream is = getAssets().open("file.xml");  
saxParser.parse(is, handler);  
  
} catch (Exception e) {e.printStackTrace();}  
}  
}  
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Output:

 output of sax parser

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