An HTTP utility library in Java

HttpUtils.java

package com.yujikosuga.http;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;

/**
 * This HttpUtils class has static utility methods for HTTP manipulation.
 * 
 * @author Yuji Kosuga
 * 
 */
public final class HttpUtils {

  /**
   * Adds HTTP headers specified in the <code>headers</code> parameter. The
   * <code>headers</code> is required to be defined in a String 2D array, such as
   * <code>{{"name","value"},{"name","value"}}</code>. .
   * 
   * @param conn the instance of HttpURLConnection to which the <code>headers</code> are added
   * @param headers the headers to be added
   */
  public static synchronized final void addHeadersToConnection(final HttpURLConnection conn,
      final String[][] headers) {
    if (conn != null && headers != null && headers.length > 0) {
      for (String[] header : headers) {
        String name = header[0];
        if (name == null)
          continue;
        String value = header[1];
        if (value == null)
          value = "";
        conn.addRequestProperty(name, value);
      }
    }
  }

  /**
   * Creates the default HTTP URL connection with the specified <code>url</code> and
   * <code>method</code>.
   * 
   * @param url the URL to be accessed
   * @param method the method
   * @return the instance of HttpURLConnection object
   * @throws IOException signals that an I/O exception has occurred
   */
  public static synchronized final HttpURLConnection createDefaultHttpURLConnection(
      final String url, final String method) throws IOException {
    URL u = new URL(url);
    HttpURLConnection conn = (HttpURLConnection) u.openConnection();
    // conn.setRequestProperty("Content-type", "text/plain");
    conn.setConnectTimeout(60000);
    conn.setRequestMethod(method);
    conn.setInstanceFollowRedirects(false);
    conn.setDoInput(true);
    conn.setDoOutput(true);
    return conn;
  }

  /**
   * Constructs a query string from a 2D array made up of a pair of an HTTP parameter and the value.
   * For example, <code>{{"a","b"},{"c","d"}}</code> becomes <code>a=b&amp;c=d</code>.
   * 
   * @param params the 2D array of query-strings
   * @return a query string
   */
  public static synchronized final String joinQueryString(final String[][] params) {
    StringBuilder sb = new StringBuilder();
    for (String[] param : params) {
      if (param.length > 0) {
        if (sb.length() > 0)
          sb.append("&");
        sb.append(param[0]); // Param name
        if (param.length > 1)
          sb.append("=").append(param[1]); // Param value
      }
    }
    return sb.toString();
  }

  /**
   * Encodes the specified string in HTTP character encoding, the default is UTF-8.
   * 
   * @param str the string to be encoded
   * @return the encoded string
   * @throws UnsupportedEncodingException if the "UTF-8" is not supported
   */
  public static synchronized String urlEncode(final String str) throws UnsupportedEncodingException {
    return URLEncoder.encode(str, "UTF-8");
  }

}