The Code

This simple Java program accepts a query term, builds the appropriate Yahoo! Search Web Services URL with that term, and parses the response. Then the program lists the top 10 URLs for that search term. The code uses XPath queries to pick out the total results available and each URL in the response.

Save the following code to a file called WebSearch.java and be sure to include a unique application ID:

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.text.MessageFormat;

/**
*Simple demonstration of the Yahoo! Web Search Service using Java 1.5's
*XML support.
*/
public class WebSearch {
// Need to have an application ID to call the Yahoo! services.
private static final String APPLICATION_ID = "insert app ID";

// URL format for the request. The simplest request includes the 
// application ID and the query. See the service documentation for 
// a list of additional parameters. 
private static final String WEB_SEARCH_URL_FORMAT =
		"http://api.search.yahoo.com/WebSearchService/V1/
 webSearch?appid={0}&query={1}";
/**

*
*Main program that takes a query and executes it as a web search
*using the Yahoo! Web Search Service.
*
*@param args Command line arguments. There should be at least 1. 
*/ 
public static void main(String[] args) throws UnsupportedEncodingException,
	MalformedURLException, XPathExpressionException,
	ParserConfigurationException {
// Make sure a query was given.
String query = null;
if(args.length == 0) {
	System.out.println("Usage: java WebSearch <query>");
	System.exit(1);
}
else {
	// Construct the query from the command line arguments. 
	query = prepareQuery(args); }

// Construct the URL. Inject the URL encoded application ID and
// the search query.
URL url = new URL(MessageFormat.format(WEB_SEARCH_URL_FORMAT,
	new Object[]{URLEncoder.encode(APPLICATION_ID, "utf-8"), 
	URLEncoder.encode(query, "utf-8")}));        
System.out.println("Request URL = " + url.toString());

// Create an XPath engine.
XPath xpath = XPathFactory.newInstance().newXPath( );

// Execute the query.
Document responseDocument = null;
try {

	// We need a Document to use XPath.            
	DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
    responseDocument = builder.parse(url.openStream()); 
} 
catch (IOException e) {
	// Error calling the service.
	System.err.println("Error calling the service: " + e.toString());
e.printStackTrace(System.err);
System.exit(1);
}
catch (SAXException e) {
// Error parsing the XML.
	System.err.println("Error parsing the XML: " + e.toString());
	e.printStackTrace(System.err);
	System.exit(1);

}
// Query the XML for the total results available.
String totalResultsAvailable = (String) xpath.evaluate( 
		"/ResultSet/@totalResultsAvailable", 
		responseDocument, 
		XPathConstants.STRING);
System.out.println("Total results available for '" + query + "' is "
		+ totalResultsAvailable);

// Query the XML for the URLs. 
NodeList urls = (NodeList) xpath.evaluate("/ResultSet/Result/Url", 
		 responseDocument, XPathConstants.NODESET);
for(int i = 0; i < urls.getLength(); i++) { 
	Node urlNode = urls.item(i); 
	System.out.println("URL " + (i + 1) + ": "
			+ urlNode.getTextContent());
   }

}
/**
* Simple method that stitches together an array of strings into
* a single string. Used to take multiple command line arguments
* and turn it into a single query string.
*
*@param args The individual strings to stitch together.
*@return A new string containing each of the strings passed in, all
*seperated by spaces. 
*/
private static String prepareQuery(String[] args) {
	String query;
	StringBuffer queryBuffer = new StringBuffer();
	for (int i = 0; i < args.length; i++) {
		queryBuffer.append(args[i]);
		if((i + 1) < args.length) {
			queryBuffer.append(" ");

		}
	}
	query = queryBuffer.toString();
	return query;

 }

}

To compile this code, open up a command prompt and type the following:

javac WebSearch.java

This should create the compiled WebSearch.class, which you can now run.