Category: Programming

String replace with callback in Java (like in JavaScript)

Nick Russler

When you use JavaScript a lot you are more or less used to the callback-hell, but i hope you love the benefits of passing functions around as much as i do.

For example when replacing a portion of a string:

"test6test12test".replace(/\d+/g, function(str){
  return parseInt(str) * 2;
});

When doing such things in Java it can be a bit of a hassle, but Lambda-Expressions to the rescue!

Convert a ByteArrayOutputStream into a ByteArrayInputStream

Nick Russler

Often while programming you find yourself glueing pre-existing code fragments together. This works out sometimes but even more often it is rather annoying. These days i had to encrypt a pdf and do some other stuff with it in java and therefore put together some libraries i found. One of these libraries offered a method to encrypt the pdf and write the result into a ByteArrayOutputStream. Later then i had to push the encrypted pdf into another method that needed it as a ByteArrayInputStream. First i simply copied the content of the ByteArrayOutputStream as byte array into the ByteArrayInputStream, but this didn’t satisfy me since i knew that the ByteArrayInputStream just needed to be initialized with the internal buffer of the ByteArrayOutputStream. Since this internal buffer is hidden from outside i made up the ByteArrayInOutStream which is a ByteArrayOutputStream that has an additional method that returns a ByteArrayInputStream which is initialized with the internal buffer of the ByteArrayOutputStream. This allows for a instant ‘conversion’ that does not use up more memory than required.

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@Asynchronous does not work from inside the same EJB

Nick Russler

I recently needed to start a method asynchronously on the server start up.

I came up with this code (pseudocode):

@Singleton
@Startup
public StartupEJB {
   @PostConstruct
   private void postConstruct() {
      worker();
   }
 
   @Asynchronous
   public void worker() {
      // Do something heavy
   }
}

This approach failed, the worker() method was not executed asynchronously.

I then found out that the Application Server (in my case JBoss) calls the method directly when it is located inside the same EJB: source.

The solution was to use a seperate EJB that launched the worker Thread:

@Stateless
public class ExecutorBean {
 
   @Asynchronous
   public void execute(Runnable command) {
      command.run();
   }
}

and

@Singleton
@Startup
public StartupEJB {
   @EJB
   ExecutorBean executorBean;
 
   @PostConstruct
   private void postConstruct() {
      worker();
   }
 
   public void worker() {
      executorBean.execute(new Runnable() {
         @Override
         public void run() {
            // Do something heavy
         }        
      });      
   }
}

Beautiful CSS3 loading animation overlay with custom message

Nick Russler

I recently stumbled over a beautiful loading animation that is completely done in CSS3 (link):

Loader Animation GIF

All i had to do was fixing a small bug (link), adding some JavaScript and adding an semi-transparent overlay, so all credits go to Hugo Giraudel.

I centered the loading animation div and added a field to display a text message.

To allow for easy display and hiding i cooked up some JavaScript that shows the overlay and puts the text message (or a default message) in the right place.

Demo:
link
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Fetch all Languages of the World (ISO 639) as Java Array

Nick Russler

Recently i needed a Java Array of all Languages, containing some unique id.

I found that ISO 639 is exactly what i needed. The list is offered by the Library of Congress in a CSV like Format (link).

So i parsed this data and thought that maybe someone can use this, either the Java Array or the Code as Example for parsing external data with JavaScript.

 Demo:

To fetch the list i used Ben Almans JSONP Proxy and Ben Nadels CSVToArray Function.
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Remove certain item or clear whole OmniFaces cache

Nick Russler

The Omnifaces o:cache Component is a useful Tool when trying to speed up you jsf powered website.

But in some situations you need to remove a certain item from the cache or you want to clear the whole cache, while there seems to be a way (Example 4) to remove single items by Key we couldn’t find a ‘official’ way to clear the whole cache.

 

Here is our Solution to the Problem:

public static boolean removeOmniCacheItem(String key) {    	
	Map<string , Object> applicationMap = FacesContext.getCurrentInstance().getExternalContext().getApplicationMap();
 
	if (applicationMap.containsKey(DefaultCacheProvider.DEFAULT_CACHE_PARAM_NAME)) {
		synchronized (DefaultCacheProvider.class) {
			if (applicationMap.containsKey(DefaultCacheProvider.DEFAULT_CACHE_PARAM_NAME)) {
				((Cache)applicationMap.get(DefaultCacheProvider.DEFAULT_CACHE_PARAM_NAME)).remove(key);
				return true;
			}				
		}
	}
 
	return false;
}
 
public static boolean clearOmniCache() {    	
	Map</string><string , Object> applicationMap = FacesContext.getCurrentInstance().getExternalContext().getApplicationMap();
 
	if (applicationMap.containsKey(DefaultCacheProvider.DEFAULT_CACHE_PARAM_NAME)) {
		synchronized (DefaultCacheProvider.class) {
			if (applicationMap.containsKey(DefaultCacheProvider.DEFAULT_CACHE_PARAM_NAME)) {
				applicationMap.remove(DefaultCacheProvider.DEFAULT_CACHE_PARAM_NAME);
				return true;
			}				
		}
	}
 
	return false;
}
</string>

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