Java AWS SDK S3 query string authentication

gistfile1.java

import java.util.Calendar;
import java.util.TimeZone;
import javax.crypto.Mac;
import javax.crypto.spec.*;
import org.apache.commons.codec.binary.Hex;
import java.security.NoSuchAlgorithmException;
import java.security.InvalidKeyException;
import java.net.URLEncoder;
import org.apache.commons.codec.binary.Base64;
import java.io.UnsupportedEncodingException;


/* method */
public String getS3Url(String filename) {

    // get your AWS credentials; remember to have AwsCredentials.properties at your resource load path
    AWSCredentials credentials = new ClasspathPropertiesFileCredentialsProvider().getCredentials();
  	String accessKey = credentials.getAWSAccessKeyId();
		String secretKey = credentials.getAWSSecretKey();
		
    // set the expiration to one hour later
		Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
		calendar.add(Calendar.HOUR, 1);
		long secondsSinceEpoch = calendar.getTimeInMillis() / 1000L;
		
		String canonicalizedResource = "/" + BUCKET_NAME + "/" + filename;
		
		String stringToSign = "GET" + "\n\n\n" + secondsSinceEpoch + "\n" + canonicalizedResource;
		
		String signature = null;
		
		try { 
			
			byte[] keyBytes = secretKey.getBytes();
			SecretKeySpec signingKey = new SecretKeySpec(keyBytes, "HmacSHA1");		
			
			Mac mac = Mac.getInstance("HmacSHA1");
			mac.init(signingKey);
			
			byte[] digest = mac.doFinal(stringToSign.getBytes());
			byte[] base64bytes = Base64.encodeBase64(digest);
			String signedString = new String(base64bytes, "UTF-8");
			
			signature = URLEncoder.encode(signedString, "UTF-8");
			
		} catch (NoSuchAlgorithmException nsae) {
			
		} catch (InvalidKeyException ike) {
			
		} catch (UnsupportedEncodingException uee) {
			
		}
		
		return "https://s3.amazonaws.com" + canonicalizedResource + "?AWSAccessKeyId=" + accessKey + "&Expires=" + secondsSinceEpoch + "&Signature=" + signature;
	}