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Help me understand this class so that I can modify it?

CyanBlue
CyanBlue used Ask the Experts™
on
Hi...  :)

I am following this blog post and try to update the class to get different data from the XML file...
   http://www.smnirven.com/?p=39

This is the actual call to the Geocoder class from the ReverseGeocodeLookupTask class...
localityName = Geocoder.reverseGeocode(currentLocation);

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The Geocoder class then calls Google Maps API to get the XML back...
InputStreamReader isr =  new InputStreamReader(connection.getInputStream());
InputSource source = new InputSource(isr);
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();
XMLReader xr = parser.getXMLReader();
GoogleReverseGeocodeXmlHandler handler = new GoogleReverseGeocodeXmlHandler();

xr.setContentHandler(handler);
xr.parse(source);

localityName = handler.getLocalityName();

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I see that it is calling GoogleReverseGeocodeXmlHandler class, which is shown below, but I don't really understand how this class works...
public class GoogleReverseGeocodeXmlHandler extends DefaultHandler
{
    private boolean inLocalityName = false;
    private boolean finished = false;
    private StringBuilder builder;
    private String localityName;
   
    public String getLocalityName()
    {
        return this.localityName;
    }
   
    @Override
    public void characters(char[] ch, int start, int length)
           throws SAXException {
        super.characters(ch, start, length);
        if (this.inLocalityName && !this.finished)
        {
            if ((ch[start] != '\n') && (ch[start] != ' '))
            {
                builder.append(ch, start, length);
            }
        }
    }

    @Override
    public void endElement(String uri, String localName, String name)
            throws SAXException
    {
        super.endElement(uri, localName, name);
       
        if (!this.finished)
        {
            if (localName.equalsIgnoreCase("LocalityName"))
            {
                this.localityName = builder.toString();
                this.finished = true;
            }
           
            if (builder != null)
            {
                builder.setLength(0);
            }
        }
    }

    @Override
    public void startDocument() throws SAXException
    {
        super.startDocument();
        builder = new StringBuilder();
    }

    @Override
    public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException
    {
        super.startElement(uri, localName, name, attributes);
       
        if (localName.equalsIgnoreCase("LocalityName"))
        {
            this.inLocalityName = true;
        }
    }
}

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The XML output looks like this...
<?xml version="1.0"?>
<AddressDetails xmlns="urn:oasis:names:tc:ciq:xsdschema:xAL:2.0" Accuracy="8">
	<Country>
		<CountryNameCode>US</CountryNameCode>
		<CountryName>USA</CountryName>
		<AdministrativeArea>
			<AdministrativeAreaName>CA</AdministrativeAreaName>
			<SubAdministrativeArea>
				<SubAdministrativeAreaName>Santa Clara</SubAdministrativeAreaName>
				<Locality>
					<LocalityName>Mountain View</LocalityName>
					<Thoroughfare>
						<ThoroughfareName>1600 Amphitheatre Pkwy</ThoroughfareName>
					</Thoroughfare>
					<PostalCode>
						<PostalCodeNumber>94043</PostalCodeNumber>
					</PostalCode>
				</Locality>
			</SubAdministrativeArea>
		</AdministrativeArea>
	</Country>
</AddressDetails>

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What I'd like to do is to get both localityName and countryNameCode at the same time...  
What I am not able to find is 'what' variable contains the whole XML string and how this GoogleReverseGeocodeXmlHandler class works since I don't see anything like a constructor and whatnot...

Thank you very much...  :)

CyanBlue
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Author

Commented:
My attempt was to call it twice like this where the handler.getLocalityName() somehow becomes null...
   localityName = handler.getCountryNameCode();
   localityName += " : " + handler.getLocalityName();

I've also attached my attempt on the GoogleReverseGeocodeXmlHandler class below...

Thanks...

CyanBlue
package com.example.geocoding;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class GoogleReverseGeocodeXmlHandler extends DefaultHandler 
{
	private boolean finished = false;
	
	private StringBuilder builder1;
	private String countryNameCode;
	private boolean inCountryNameCode = false;
	
	private StringBuilder builder2;
	private String localityName;
	private boolean inLocalityName = false;
	
	public String getCountryNameCode()
	{
		return this.countryNameCode;
	}
	
	public String getLocalityName()
	{
		return this.localityName;
	}
	
	@Override
	public void characters(char[] ch, int start, int length)
			throws SAXException {
		super.characters(ch, start, length);
		
		if (this.inCountryNameCode && !this.finished)
		{
			if ((ch[start] != '\n') && (ch[start] != ' '))
			{
				builder1.append(ch, start, length);
			}
		}
		
		if (this.inLocalityName && !this.finished)
		{
			if ((ch[start] != '\n') && (ch[start] != ' '))
			{
				builder2.append(ch, start, length);
			}
		}
	}
	
	@Override
	public void endElement(String uri, String localName, String name)
			throws SAXException 
	{
		super.endElement(uri, localName, name);
		
		if (!this.finished)
		{
			if (localName.equalsIgnoreCase("CountryNameCode"))
			{
				this.countryNameCode = builder1.toString();
				this.finished = true;
			}
			
			if (builder1 != null)
			{
				builder1.setLength(0);
			}
			
			if (localName.equalsIgnoreCase("LocalityName"))
			{
				this.localityName = builder2.toString();
				this.finished = true;
			}
			
			if (builder2 != null)
			{
				builder2.setLength(0);
			}
		}
	}
	
	@Override
	public void startDocument() throws SAXException 
	{
		super.startDocument();
		builder1 = new StringBuilder();
		builder2 = new StringBuilder();
	}
	
	@Override
	public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException
	{
		super.startElement(uri, localName, name, attributes);
		
		if (localName.equalsIgnoreCase("CountryNameCode"))
		{
			this.inCountryNameCode = true;
		}
		
		if (localName.equalsIgnoreCase("LocalityName"))
		{
			this.inLocalityName = true;
		}
	}
}

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Top Expert 2016
Commented:
All that is absolutely standard SAX parsing. It's easy to read up on it:

http://www.cafeconleche.org/books/xmljava/chapters/ch06.html

Author

Commented:
Awesome...  Now I understand(sorta) how those methods works and all...  Appreciate it...  ;)

CyanBlue
Top Expert 2016

Commented:
:)