Sample code demonstrating how to parse the XMP metadata in an image using javax.imageio.metadata. Written to answer this stackoverflow question: http://stackoverflow.com/a/13748517/1002469

imgmeta.java

import java.io.*;
import java.util.*;

// for imageio metadata
import javax.imageio.*;
import javax.imageio.stream.*;
import javax.imageio.metadata.*;

// for xml handling
import org.w3c.dom.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;

import javax.xml.parsers.*;

public class imgmeta {
  // Very lazy exception handling
	// This is just a quick example
	public static void main(String[] args) throws Exception {
		String filename = args[0];
		
		File file = new File(filename);
		ImageInputStream imagestream = ImageIO.createImageInputStream(file);
		
		// get a reader which is able to read this file
        Iterator<ImageReader> readers = ImageIO.getImageReaders(imagestream);
		ImageReader reader = readers.next();
        
		// feed image to reader
		reader.setInput(imagestream, true);

		// get metadata of first image
		IIOMetadata metadata = reader.getImageMetadata(0);
		
		// get any metadata format name
		// (you should prefer the native one, but not all images have one)
		// String mdataname = metadata.getNativeMetadataFormatName(); // might be null
		String[] mdatanames = metadata.getMetadataFormatNames();
        
		String mdataname = mdatanames[0];
        
		Element metadatadom = (Element) metadata.getAsTree(mdataname);
		
		// String metadata_in_xml = xmlToString(metadatadom);
		
		// now print it:
		Document xmp = getXMP(metadatadom);
		System.out.print(transformXML(xmp));
	}
	
	
	public static String transformXML(Node xml) throws Exception {
		// now let's serialize to an XML string
		// javax.xml.transform.Transformer takes xml sources
		// in one representation and transforms them to xml
		// in another representation
		// Representations include: DOM, JAXB, SAX, stream, etc
		StringWriter writer = new StringWriter();
		
		Transformer transformer = TransformerFactory.newInstance().newTransformer();
		transformer.transform(new DOMSource(xml), new StreamResult(writer));
		
		return writer.toString();
	}
	
	public static Document transformXML(String xml) throws Exception {
		StringReader reader = new StringReader(xml);
		Document doc = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
		Transformer transformer = TransformerFactory.newInstance().newTransformer();
		
		transformer.transform(new StreamSource(reader), new DOMResult(doc));
		return doc;
	}
	
	public static Document getXMP(Element metadata_dom) throws Exception {
		// There are many more robust ways of selecting nodes
		// (e.g. javax.xml.xpath), but this is for a simple example
		// that only uses the native DOM methods
		
		// This is very brittle because we're making assumptions about
		// the metadata_dom structure. There are two sources of brittleness:
		
		// 1. The metadata format from `metadata.getMetadataFormatNames()`.
		//    You should probably settle on a standard one you know will
		//    exist, like 'javax_imageio_1.0'
		// 2. How the image stores the metadata. Usually XMP data will
		//    be in a text field with keyword 'XML:com.adobe.xmp', but
		//    I don't know that this is *always* the case.
		
		// the code below assumes "javax_imageio_png_1.0" format
		NodeList iTXtEntries = metadata_dom.getElementsByTagName("iTXtEntry");
		Element iTXtEntry = null;
		Element entry = null;
		for (int i = 0; i < iTXtEntries.getLength(); i++) {
			entry = (Element) iTXtEntries.item(i);
			// System.out.print(entry.getAttribute("keyword")+"\n");
			// System.out.print(com_adobe_xmp+"\n");
			if (entry.getAttribute("keyword").equals("XML:com.adobe.xmp")) {
				iTXtEntry = entry;
				break;
			}
		}
		if (iTXtEntry == null) {
			return null;
		}
		
		String xmp_xml_doc = iTXtEntry.getAttribute("text");
		// xmp_xml_doc is now an xml document string
		
		// If you want to parse it as an XML document, use an XML
		// parser.
		Document xmp_doc = transformXML(xmp_xml_doc);
		
		return xmp_doc;
		
	}
}