Archive for the ‘Java’ Category

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Hashing Passwords

Wednesday, December 5th, 2007

Here is some code that you can use to hash passwords or other secrets in Java. I usually prefer to have such methods in a separate utility class:

protected static MessageDigest getDigest() throws NoSuchAlgorithmException {
	if (digest == null) {
		digest = MessageDigest.getInstance(&qout;MD5&qout;);
	}
	return digest;
}
 
public static byte[] digestString(String s) {
	if (s == null) return null;
	try {
		MessageDigest digest = getDigest();
		digest.update(s.getBytes());
		return digest.digest();
	} catch (Exception e) {
		log.error(&qout;Digesting problem:&qout;, e);
	}
	return null;
}
 
public static String encodePassword(String s) {
	byte b[] = digestString(s);
	if (b == null) return null;
	String rc = new String(Base64.encodeBase64(b));
	if (rc.length() > 50) rc = rc.substring(0, 50);
	return rc;
}

Use the function encodePassword() to hash your string. Please note that the hash value is limited to a length of 50 characters.

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Posted in Java | No Comments »

Configuring logging in a Java web application

Tuesday, December 4th, 2007

Here is a short HOWTO for making some initial configuring when using Commons logging or log4j. Additionally this post will describe how to set the default locale in a servlet environment.

First you will need to create a new class derived from HttpServlet.

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package mypackage;
 
import java.util.Locale;
 
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import org.apache.commons.logging.LogFactory;
import org.apache.log4j.PropertyConfigurator;
 
/**
 * Initializes log4j so it reads its configuration from WEB-INF directory and sets default locale.
 * @author Ralph Schuster
 *
 */
public class LogConfiguratorServlet extends HttpServlet {
 
   /**
    * Serial ID.
    */
   private static final long serialVersionUID = -5756062055681369027L;
 
   private static final String DEFAULT_FILE = "WEB-INF/log4j.properties";
 
   private static final String DEFAULT_LOCALE = "en_US"; // You can use "en", too.
 
   /**
    * Initializes log4j and sets default locale.
    */
   public void init() {
      // Do the log4j configuration
      String prefix =  getServletContext().getRealPath("/");
      String file = getInitParameter("config-file");
      // if the config-file is not set, then no point in trying
      String s = null;
      if (file != null) {
         s = prefix+file;
      } else {
         s = prefix+DEFAULT_FILE;
      }
      PropertyConfigurator.configure(s);
      LogFactory.getLog(getClass()).debug("log4j configuration file: "+s);
 
      // Do the locale configuration
      s = getInitParameter("locale");
      if (s == null) s = DEFAULT_LOCALE;
      Locale available[] = Locale.getAvailableLocales();
      for (int i=0; i<available.length; i++) {
         if (available[i].toString().equals(s)) {
            Locale.setDefault(available[i]);
         }
      }
      LogFactory.getLog(getClass()).debug("Default locale set to: "+Locale.getDefault());
   }
 
   /**
    * Does nothing.
    */
   public void doGet(HttpServletRequest req, HttpServletResponse res) {
   }
 
}

You then need to deploy the class in your servlet container and adjust the web.xml file:

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   <servlet>
      </servlet-name>log4j-init</servlet-name>
      <servlet-class>mypackage.LogConfiguratorServlet</servlet-class>
 
      <init-param>
         <param-name>config-file</param-name>
         <param-value>WEB-INF/log4j.properties</param-value>
      </init-param>
      <init-param>
         <param-name>locale</param-name>
         <param-value>de_DE</param-value>
      </init-param>
 
      <load-on-startup>1</load-on-startup>
   </servlet>

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SimpleCaptcha for Servers

Wednesday, November 21st, 2007

Currently there is a bug in SimpleCaptcha library that prevents it running in non-graphics environments. It will throw a java.awt.HeadlessException. Although the code does not rely on various graphics classes, they were left causing this problem.

I fixed the code and recompiled it. You can download the fixed JAR file here. Do not forget to set the system property java.awt.headless to true, e.g. by specifying Djava.awt.headless=true at command line.

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Posted in Java | 9 Comments »

TYPO3-like templating with Java

Tuesday, November 20th, 2007

Here is a class I wrote to apply TYPO3-like templating mechanism within Java. I am quite familiar with that kind of templates, so I decided to use it within one of my projects, too. The implementation requires Java 5.

Java Templating class

You need to adopt the class’ package though ;-)

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Posted in Java, Typo3 | 1 Comment »

URL Parameter Transforming

Friday, November 16th, 2007

Need to transform URL parameters and decode values such as “Hello%20World!”? Here is how:

Perl:

$s =~ s/%([\da-f][\da-f])/chr( hex($1) )/egi;

Java:

s = java.net.URLEncoder.encode(s, "UTF-8");

PHP:

$s = urldecode($s);

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Posted in Java, Perl, PHP | No Comments »

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