Web search using Yahoo Web Search API

YahooWebSearchAPI.java

package jp.youtalk;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.text.ParseException;
import java.util.LinkedList;
import java.util.List;

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

public class YahooWebSearchAPI {
	private final String appid;
	private final int size;
	private final String url = "http://search.yahooapis.jp/WebSearchService/V2/webSearch";
	private final String charset = "UTF-8";
	private final XPath xpath = XPathFactory.newInstance().newXPath();

	public YahooWebSearchAPI(final String appid, final int size) {
		this.appid = appid;
		this.size = size;
	}

	public synchronized List<String> searchWikipediaSummary(final String query) {
		List<String> results = new LinkedList<String>();

		try {
			String xml = search(new URL(makeQuery(query + "+Wikipedia")));
			Document doc = xmlToDocument(xml);

			for (int i = 0, size = size(doc, "ResultSet/Result"); i < size; i++) {
				String s = value(doc, "ResultSet/Result[" + (i + 1) + "]/Summary");

				while (s.indexOf("（") != -1 && s.indexOf("）") != -1) // remove rubies
					s = s.substring(0, s.indexOf("（")) + s.substring(s.indexOf("）") + 1, s.length() - 1);
				if (s.indexOf("。") != -1) // extract leading one sentence
					s = s.substring(0, s.indexOf("。") + 1);

				results.add(s.trim().replace(" ", ""));
			}
		} catch (Exception e) {
			e.printStackTrace();
			return searchWikipediaSummary(query); // try again
		}

		return results;
	}

	public static void main(final String[] args) {
		YahooWebSearchAPI api = new YahooWebSearchAPI("appid here", 5);
		List<String> results = api.searchWikipediaSummary("奈良");

		for (String r: results)
			System.out.println(r);
	}

	private String makeQuery(final String sentence)
			throws UnsupportedEncodingException {
		return url + "?appid=" + appid +
			"&query=" + URLEncoder.encode(sentence, charset) + "&results=" + size;
	}

	private int size(final Document doc, final String expression)
			throws XPathExpressionException {
		NodeList list = (NodeList) xpath.evaluate(expression, doc, XPathConstants.NODESET);
		return list.getLength();
	}

	private String value(final Document doc, final String expression)
			throws XPathExpressionException {
		return xpath.evaluate(expression, doc);
	}

	private Document xmlToDocument(final String xml)
			throws IOException, SAXException, ParserConfigurationException {
		StringReader sr = new StringReader(xml);
		InputSource is = new InputSource(sr);
		Document doc = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(is);

		return doc;
	}

	private String search(final URL url)
			throws IOException, ParseException {
		HttpURLConnection connection = (HttpURLConnection) url.openConnection();
		connection.setRequestMethod("GET");
		connection.setDoOutput(true);
		connection.connect();

		InputStream is = connection.getInputStream();
		InputStreamReader isr = new InputStreamReader(is, charset);
		BufferedReader br = new BufferedReader(isr);
		StringBuilder sb = new StringBuilder();
		String line;

		while ((line = br.readLine()) != null) {
			sb.append(line);
			sb.append("\n");
		}

		br.close();
		connection.disconnect();

		return sb.toString();
	}

}