AEM integration with webp

A question from my colleagues in regards to AEM’s support for webp started a research path. Since, I took more than 1 year pause from AEM, I started looking around for the possibility of serving also webp images, for all the images already in DAM.

As a first step I started ask the community on stackoverflow and Adobe Forum. The answer received was to use a webp java library that provides support for reading and writing webp images .

Note: You will notice I have usedcom.github.nintha library. At the end of the article I will explain the reasoning for it and how I actually ditched it to work.

The steps for resolving this were:

  1. To add the 3rd party jar to AEM
  2. Create a simple servlet that receives as queryparam the image path as and returns the webp image.

Adding the 3rd party jar

In AEM one can install via in Apache Felix only bundled jar, for the simple jars, one can embed them using the maven-bundle-plugin in tree steps:

  1. Add the library jar to your application pom.xml (the main one)

2. Modify the pom.xml from the core app to add the dependency and embed the jar. The core/pom.xml will have something like:


Things to mention: the Embed-Dependency tag needs to be populated with the artifactId. The <Embed-Transitive> tag specifies to embed also the dependencies of the embedded jar. (eg. the webp-imageio-core has as dependency org.scijava – native-lib-loader, which will be embedded as well)

In order to test that your 3rd party was successfully embedded, one can take a look at the bundle information:

Verify that:
– Bundle Classpath includes the 3rd party jar
– The manifest header contains the embedded dependencies, artifacts and transitive set as expected

Create the Servlet to transform to webp

For the purposes of this POC, it will be only a basic Servlet, it can be enhanced, of course to work with image renditions, or to work receive the path as a suffix – which would be the right way as we want the images to be cached.

package andra.core.servlets;

import com.luciad.imageio.webp.WebPWriteParam;
import org.apache.felix.scr.annotations.Properties;
import org.apache.felix.scr.annotations.Property;
import org.osgi.framework.Constants;

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.servlet.ServletException;
import java.awt.image.BufferedImage;

@SlingServlet(paths = "/bin/webpTransformer",
methods = HttpConstants.METHOD_GET
@Property(name = Constants.SERVICE_DESCRIPTION, value = "WebP Transformer Servlet")
public class WepServlet extends SlingSafeMethodsServlet {

public static final String IMAGE_WEBP = "image/webp";

protected void doGet(SlingHttpServletRequest request, SlingHttpServletResponse response) throws ServletException, IOException {

BufferedImage image = getImage(request);

// Obtain a WebP ImageWriter instance
ImageWriter writer = ImageIO.getImageWritersByMIMEType(IMAGE_WEBP).next();

// Configure encoding parameters
WebPWriteParam writeParam = new WebPWriteParam(writer.getLocale());
ImageOutputStream outputStream = new MemoryCacheImageOutputStream(

// Configure the output on the ImageWriter

// Encode
writer.write(null, new IIOImage(image, null, null), writeParam);


private BufferedImage getImage(SlingHttpServletRequest request) throws IOException {
ResourceResolver resourceResolver = request.getResourceResolver();
String path = request.getParameter("path");
Resource res = resourceResolver.getResource(path);
Asset asset = res.adaptTo(Asset.class);


Why and how nintha ?

A question I would ask is why use nintha over luciad, as in the end nintha is just a luciad wrapper. Of course, I always try to use the standard lib, where possible, however when embedding luciad compiled on my machine I would get the following error:

Could not initialize class com.luciad.imageio.webp.WebPEncoderOptions
Cannot serve request to /bin/webpTransformer in andra.core.servlets.WepServlet

java.lang.NoClassDefFoundError: Could not initialize class com.luciad.imageio.webp.WebPEncoderOptions
at com.luciad.imageio.webp.WebPWriteParam.(
at com.luciad.imageio.webp.WebPWriter.getDefaultWriteParam(

After a couple of days, I decided to give nintha a go. However, it did not go as smooth as I wanted, as know I would receive:

org.scijava.nativelib.NativeLibraryUtil Problem with library

Meaning, that the native library included in nintha was not compatible with the OS the app was running. So, I had to add compile the native app on my local machine, add it manually to the nintha library and recomile. This is not a solution I like as it would be a downside when migration to another server – the library needs to encapsulate the native app for the specific environment.

Javaist learning Python – Part 2 – conditions

I will write about what something I found funny – the conditions

  1. Python has a elif statement. This makes the code easier to read. Python you have a +1 from me for this
  2. Ok… now we go to the part where we find that one does not need to check for a boolean condition. Not only it does not need to check for this, it is advised NOT to check against False, True or None (a singleton that is somehow similar to the null in Java). Everything except the next statements are considered True(This reminded me of highschool and C++):
    • None
    • False
    • zero – for numeric types
    • empty dictionaries, sequences
    • 0 returned when calling __length__
    • False returned when __nonzero__ is called
  3. Now, an even stranger thing: one can have an else after a for… say whaat? yep… One can face something like
    for loop:
        if condition:
    So, what is this all about? The statement is executed when after the program finished the loop… Every time, with one exception: when a break was executed inside the loop. I still have mixed feelings about this, but probably after using more of it, it will come natural.

This was all from my Python adventure till this moment.

Javaist learning Python – Part 1

I always enjoyed stuff that had to do with programming languages and learning how to set your mind to new things/paradigms. One of my favourite courses in the University was Logic and Functional Programming – learning Prolog and LISP (Let’s Insert Some Parenthesis :D).

I played a little bit with Python for my Mater’s Thesis (Static vs Dynamic Typed Programming Languages) some years ago and I always wanted to go a little bit more in depth with it. So, now I considered it to be a great time to restart playing with Python.

The syntax I consider it to be pretty straightforward and there is quite a good documentation on the internet. But, somehow I felt I was missing the Java API docs format. For me it is more convenient to search for something and see what else I can do with that object. Also, the font size seems to be kind of unfriendly – small and a little bit cramped(I know one can resolve this with zoom on the page). I will probably get used to the documentation, but in the meantime I will crave for Java documentation.

Even though, I knew it is not a pure object oriented programming language, is it still funny to white something “outside an object”, but this did not bother me at all, on the contrary, I found it really easy to get started writing code.

Another thing I really like the command line interpretor, that can be run from the command line. Having this is really helpful for the people that have their first contacts with Python. One can actually test something before adding it to a program.

That’s all for now, but I will keep posting further impressions :).

Collections quick review

There are times in our developer lives when we just settle with a range of implementations without thinking of the reasons behind it, or without having any valid argument in order to use one implementation over another.

Some time ago I was having a discussion with a friend [which is a big data developer] about the importance of choosing the right collection. He gave an example on how using the wrong implementation a job took over 3 hours, after changing the implementation of the collection used the same job needed 5 minutes to complete.

Below can be seen a table with basic information about different implementations of collections

Implementation Ordered Sorted Syncronized Nulls Notes
HashMap One null key andno null values
Hashtable* No null keys and no null values
TreeMap Accepts nulls as keys and value
LinkedHashMap Accepts nulls as keys and value Faster iterations than HashMap but slower inserts and remove
HashSet Accepts null
TreeSet Accepts null
LinkedHashSet Accepts null
ArrayList Accepts null Fast iterations
Vector Accepts null
LinkedList Accepts null Fast iterations and deletion
PriorityQueue Accepts null

* There is not a typo: Hashtable is the special kid that does not have camel case

PS: This is just a quick review for more about how each works, I suggest visiting the API.

Work rules – loved it, please amend it

I am a happy iphone, ipad, Macbook Pro user that is just in love with Google: the products, the work, the culture(as much as I know about it: Who would not like to ride the bike inside the office?). It is no wander that the next day after I heard this interview with the  SVP, People Operations Laszlo Bock I got the Kindle edition of his book.
Actually “Work rules!” was my non-technical vacation book. (Yes, I read about work rules and how work [can] rule during my holidays ).
One cannot dislike a book in which the sincerity can be felt: Laszlo even admits the doubts he has when he became a Googler. Usually when I read a book/article, that is said to be about team management, I get kind of septic: same old tricks rephrased. Well, that was definitely not the case about “Work rules”. It provides not only lots of results form “experiments” that took place at Google (and as Antoine de Saint-Exupéry said: Grown-ups love numbers … ), but also some rules that could be applied in order to achieve having an awesome (Googlish) work place. There were plenty of times when I was asked: “Why are you giggling?” Do not get me wrong it is a serious book about a serious matter, but written in a way that it is easy to read, by inserting anecdotes from Googlers day by day work time.


There is something I do not entirely agree with: the cover of the book: It is said that it will change the way one lives and leads. Ok, I know the work is part of our life and the way we work is part of the way we actually live (see the below diagram)

but I felt this is not a book for managers or people that want to become managers/leaders. I felt that this is a book for everyone – no matter of the label she/he has. I am pretty sure that anyone can apply most of the rules stated in its regular working day. So, the amend I would like to do see is the cover to say : “THAT WILL TRANSFORM HOW YOU LIVE, WORK AND LEAD”.

Laszlo, I am looking forward to reading the second edition and hope it has the amended cover!
P.S. I hope the next one has some data analysis in regards to the number of people applying for a job at Google (before and after this book was released).

So what’s that difference again? Abstract class vs Interface

Everything was nice and pretty clear before beautiful Java 8 was born.  One could define:

(1) Abstract class as being a class declared abstract (usually, but not necessary, contains at least one abstract method).

(2) Abstract method as being one method that is declared, but for which no implementation was provided.

(3) Interface as a 100% abstract class.

Even though, not all the differences are explained in these statements, these would have been acceptable definitions.

And then Java 8 was brought into the world, and the new feature (considered by some the best new enhancement) : default and static methods for interfaces. Non-abstract methods defined directly in the interface. This implies that (3) became obsolete and the magic question arise:

What is the difference between an interface and abstract class? 

Abstract class Interface
Default methods any method that is not abstract can be considered defaultit is not marked with default modifier marked withdefault modifier
Static methods static modifier required see below examples static modifier required
Non-Constants variables can be defined all the variables are implicitly public static final
A Java class can extend just one class (abstract or concrete) implement multiple interfaces
A Java interface cannot extend/implement an abstract class can extend multiple interfaces
The first concrete class extending the abstract class must implement all abstract methods implementing the interface must implement all abstract methods
Implicit modifiers for variables No implicit modifiers public static final
Implicit modifier for methods No implicit modifiers the non-static & non-default methods are implicitly public abstract
When to use … ? when the code is shared amongst related classes when the code is shared among unrelated classes

So, let’s revisit the definition of an interface. I would like to go for this one:

Interfaces are abstract data types that provide a contract between its users and its providers.

Here you have a nice example to start discovering the differences between abstract classes and interfaces!

import static java.lang.System.out;
class Main {
 public static void main (String[] args) throws Exception { //Mother mother = new Mother(); DOES NOT COMPILE
 //AnInterface interface = new AnInterface(); DOES NOT COMPILE
 Mother child1 = new Child();
 AnInterface child2 = new Child();
 Child child3 = new Child();
 //calling static fields


 //caling static methods
 //calling default methods

 //child2.staticInterfaceMethod(); DOES NOT COMPILE
 //child3.staticInterfaceMethod(); DOES NOT COMPILE
 //Child.staticInterfaceMethod(); DOES NOT COMPILE
 //calling default methods



abstract class Mother {

 public static final String ABSTRACT_CLASS_NAME = "Mum name";

 public static void staticMotherMethod() { //the access modifier is not implied
 out.println("static Mother Method");

 public void defaultMotherMethod() { //the access modifier is not implied
 out.println("Mother default");

 public void defaultMotherMethod1() {
 out.println("Mother default 1"); //the access modifier id not implied

 public abstract void abstractMotherMethod() ;

interface AnInterface {

 String INTERFACE_NAME = "Interface name"; //implicit public static final

 default void defaultInterfaceMethod() { //implicit public
 out.println("default interface method");

 default void defaultInterfaceMethod1() {
 out.println("default interface 1");

 static void staticInterfaceMethod() { //implicit public
 out.println("static inteface method");

 void abstractInterfaceMethod(); //implicit public abstract

class Child extends Mother implements AnInterface {
 public void abstractInterfaceMethod() {
 out.println("Child abstractInterfaceMethod");

 public void abstractMotherMethod() {
 out.println("Child abstractMumMethod");

 public void defaultMotherMethod1() {
 out.println("Child default method");

 public void defaultInterfaceMethod() {
 out.println("Child interface method");


Hope you had fun! 🙂 Till the next post hope you enjoy Java!

Everybody likes promotions

…of course, I talk about the Java numeric promotions. Probably everyone knows what she/he should do to get promoted, but what about the Java numeric promotions?

A. What does promotion mean?

The numeric promotion represents the automatically made conversion from a smaller numeric type to a wider numeric type when a binary aritmetic operation is made. [So it seems that this does not require hard work for some :D]

Just a small recap about the types and their length can be seen in the below table:

Type length in bytes length in bits
byte 1  1 * 8 = ?
short 2 please guess
int 4 hard one
long 8  ∞ * ∞ (reversed)
float 4 32
double 8 be my guest
char 2 16

B. What is required to get a promotion?

Just operands of the same type can be used for a binary operation. In order to achieve that there are some clear rules about how promotions occur:

1. When applying the operator for operands of different types: the smaller numeric type is promoted to the larger number type

2. When applying the operator for an integer value and a floationg point : the integer value is promoted to the floating point value.

3. Byte, short, char are automatically promoted to int when using binary operator.

4. The result of the operation has the type of the operands. [Mind the fact at the time the operator is applied the operands have the same type]

C. Tiny games with promotions

1. Let’s apply the above mentioned rules for the follwing example:

byte byteA = 1;
byte byteB = 2;
//byte byteSum = byteA + byteB;
//short shortSum = byteA + byteB;
int intSum = byteA + byteB;

Applying rule number 3 it is clear that the commented out lines of code result in a not very elegant compilation error:

 error: possible loss of precision
 byte byteSum = byteA + byteB;
 required: byte
 found: int

2.  Apply the rules and say the type .

int intA = 1;
float floatB = 2.0f;
byte byteC = 3;
____ sum = intA % byteC + floatB;

Yep, first rule number 1 is applied for byteC and the result of intA % byteC would be an integer, then this result is promoted to float and the returned value is float.

3. Let’s try another game. Take the following code:

byte byteA = 1;
byte byteB = 2;
byteB += byteA;

What happens? If you said “Compilation failure”, please, think again. As I said the promotion is applied only for binary arithmetic operations and += is actually considered a compound assignment operation, but that is another story 🙂

People tend do enjoy promotions ;). I bet you get a promotion every day, so enjoy today!

And I fell in love with the date…Java 8 Date

Love is in the air year after year in the period when winter and spring fight for power.

In the week that Java8 turns one I am going to speak about the date I fell in love with…Java 8 Date.

Even though I have never considered the previous implementation of Dates as being a pain (just a little bit verbose :p) I am really appreciative and using it made me fall instanlty in love with the new Date.

What do I really like about Date? You may find listed below some(not all) reasons:

  • The possibility to use classes specify/use exactly what you need:

Why should I be forced to store the specific date (usually 1st January 1970) when I just need the hours?  was a question that arose probably in many situations. [I would really want to know how many GB of data occupies the 1st January 1970]

Java 8 resolved the issue with adding specific classes LocalDateTime, LocalDate and LocalTime classes for the “un-timezoned” feature and for each of these provides the zoned class, which stores also the timezone for each of them.

Also, the precision one needs to use can be specified

  • The easiness to get a reference to a new instance of a Date.

Seems like a dream not to use a Calendar class to get a new instance of a Date class:

LocalDateTime thisMoment =;

LocalDate java8LauchDate = LocalDate.of(18, Month.MARCH, 2014)

LocalDate forTheNostalgics = LocalDate.ofEpochDay(1);

  • The beauty of the Period and Duration

Until this moment we specified precise moment in time, but sometimes we need to use an interval rather than specific points in time.

Period oneYearTwoMonthsThreeDays = Period.of(1,2,3);

and Period’s little brother (used for intervals within a day):

Duration snoozeDuration = Duration.ofMinutes(10);

  • One can do maths![How can one not love that]

The addition/substraction of specific periods is just a bliss:

LocalDateTime now =;

  •  The usage of the “normal” number for the month.

Just imagine in a previous Java version my birthday would have been declared like. Ok, I am  a developer and used with 0-index, but I could not just set my brain to use 5 0 for my birthday[Now that you know when my birthday is, you can send me birthday cards or presents and I do not mind receiving them before of after my bithday…so it’s still not too late 🙂 ]

Happy birthday, Java8!

And for you: hope you all have dates as good as the Java 8 ones!

What if?

Being the first post I write about books I need to say something  about the relationship between books and I:

  1. I usually read 2 books at a time
  2. I choose the books by:
    •  friend’s recommandation
    • goodreads or other site’s newsletter/recommandations
    • beautiful cover in a library
    • title
  3. I usually give a book 100 pages to impress me. In case this does not happen I leave it behind without feeling sorry
  4. I buy as gifts for others books I want to borrow
  5. During the winter I enjoy reading near the fireplace or any other heating source :p

Goodreads recommended for me in October a book that seemed to be interesting : “What If? Serious Scientific Answers to Absurd Hypothetical Questions” by RANDALL MUNROE. The next minute I was on Amazon downloading the sample for this book, googling for information on the author( a former NASA roboticist, curently webcomic) I instantly felt inlove with the title, the idea behind this book and the way it was written. Even though it had to wait patinently in my pipeline till the winter holiday, when I came back to the rest of the book the same feeling reappeared. This is a book that:

  • makes you wonder/think ( sometimes I used google for further information about phisics topics I’ve forgotten since highschool)
  • makes you smile
  • and just gives you a hint of how perfect this universe is.

I was also impressed by the fact that there are also treated questions that usually are associated with philosophy rather than any exact science like: “is there only a soul-mate for a person?”
During the time I was reading it I asked myself several times : “wouldn’t a book like this make any kid more interested in mathematics, phisics or chemistry?” I did not get any answer, but in case the answer is “no” probably nothing would :).

p.s.: this is not a review. Here are just my thoughts on this book. I consider it to be a book that can be read by anyone from the students in secondary school without superior age limit.

Mule ESB create MongoDB 2dsphere Index

Mule ESB 3.5 works like a bliss with MongoDB 2.4.9,  providing an easy way to configure the connection. A template for MongoDB configuration looks like:

<mongo:config doc:name=”MongoDb”

The MongoDB connector provided, gives the user the possibility to easily configure almost any database operation.

But what should be done when the operation we want to perform is not quite straightforward? An example to this is creating a 2dsphere index. Even though, the MongoDB connector provides “Create Index” operation, one can configure just the order of the index, but not its type.

An approach for these situations without the necessity to  write custom code is to use the “Execute command” operation provided. This operation is a representation of db.runCommand.

So, comming back to the 2dsphere index, the creation using db.runCommand would normally look like:

db.runCommand( { eval :function() {db.collectionName.ensureIndex( {geolocation : ‘2dsphere’} ) } } )

In case we want to create the index using Mule the following connector configuration is to be done:

MongoDB mule

or if you prefer XML version, the previous photo is translated into:

<mongo:execute-command config-ref=”MongoDatabase” commandName=”eval” commandValue=”function(){db.collectionName.ensureIndex({geolocation : ‘2dsphere’})}” doc:name=”Mongo DB”/>

The usage of the “Execute command” operation seems to be straightforward, but at the moment this article was written the documentation for mule:execute-command was lacking a proper example.