如何根据IP地址获取地理位置？

/**
     * 根据IP地址获取地理位置
     */
    public String getAddressByIP(String ip) {
        try {
            URL url = new URL("http://www.ip138.com/ips138.asp?ip=" + ip);
            URLConnection conn = url.openConnection();
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    conn.getInputStream(), "GBK"));
            String line = null;
            StringBuffer result = new StringBuffer();
            while ((line = reader.readLine()) != null) {
                result.append(line);
            }
            reader.close();
            char[] address=null;
            address = result.substring(result.indexOf("主数据：") + 4,
                    result.indexOf("</li><li>参考数据"));
            address = ip.toCharArray();
            System.out.println(address);//输出地址
        } catch (Exception e) {
            e.printStackTrace();
        }
        return address;
    }