Friday, November 7, 2014

Alfresco Summit 2014 - London - My Takeaways!

Alfresco summit 2014 started on 7th October (which was also my birthday and my Zaizi first year anniversary!!!) at London Hilton Metropole hotel.

This was my first Alfresco summit experience, which turned out to be very exciting and rewarding.

On the first day, I got the opportunity to attend full day Alfresco training by Rui Fernandes, Alfresco international trainer, to get hands-on experience with web scripts.

Then, we had the "partner drinks" event, which was a networking event for all the Alfresco partners. (Special thanks for Zaizi London friends who wished me for my birthday and and sang happy birthday song in the event to make me feel home, and also for Zaizi Colombo friends who sent me surprise birthday gifts!)

There, people were interested about Zaizi - Connecting Intelligence slogan and they were so curious to know what we are doing with semantics, NLP and machine learning at Zaizi.
.
The summit sessions were officially started next day followed by the product keynote by Thomas DeMeo, the VP of product management for Alfresco

The first session I attended was " Activiti in the Event-Driven Architecture" by Robin Bramley Chief Scientific Officer for Ixxus. It was about using complex event processing in BPM for business activity monitoring (infer co-related event or patterns). The solution uses Activiti, Apache Camel and Esper. It was interesting to see how organisations can gain meaningful insight for business operations using their day to day events.

The next session was "Whats new in Alfresco 5 search?” Andy Hind and Mike Farman from Alfresco
. There, the presenters explained the new search enhancements such as Alfresco faceted search, auto-suggest and spelling and performance improvements, achieved using new SOLR4 features.

The next session, namely "Declarative configuration of share session” by Dave Draper from Alfresco focused on creating dynamic UI component design using Akiue framework. There was thunderous applause from the audience, when the speaker created a simple 'things to do' UI application in 3 mins.

Next one was the lightening talks session. It was a challenging session for speakers, because the slides were auto playing and each speaker got only 5 mins to talk, yet it was fun for the audience. The "easy edit" application, which helps to open the documents in their native application itself (E.g., MS doc in MS Office) for edit was a cool feature. I exactly do not remember if this was the session which the speakers took off their shirts to release their new product. ;)

The last session for the day was "Top 10 tricks to improve Alfresco performance” by Sergio from Zaizi. Using his experience with Alfresco, he explained different SOLR settings, Alfresco configuration settings and clustering mechanisms for share and alfresco that should be in place to improve Alfresco performance.

Also, he mentioned one more important thing that applies not only with Alfresco performance, but with anything we do in our lives. That is…  “What ever you do, do it with passion!”

After that, we attended the awesome evening party at Palace Suite, with The band Sway Allstars.
Too bad I missed the Zaizi after party at Apres London, as I had to go back to hotel for my speech preparation for next day. #LastMinutePanic

Next day, I presented in the session “Set your content straight” which talks about applying machine learning techniques in Alfresco to enhance metadata and search capabilities.

Then, Ainga, CEO Zaizi explained few customer use cases where we can take the advantage of technologies such as content analytics, data linking, intelligence search and machine learning to solve business problems in his session "Content Intelligence: Advanced Information Technologies for Alfresco"
.
Another session that I was interested about was "Indexing and searching speech contained in audio and video content” by Romain Guinot from Alfresco.

There, they have integrated Pocketsphinx : speech-to-text engine with Alfresco transformations to enable video and audio content indexing and search. Audio and video provides better help when it comes to grasp a particular perception effectively, yet they are consuming more network bandwidth than other medias such as text.

So, this provides a nice solution for the above issue by indexing the actual content of the audio or video files and make them available for searching.

Then, Lucas was presenting the session on "Scale Audit & Reporting with a NoSQL Architecture”.

Last but not least: Bringing Alfresco to Google glass! In this presentation, it was demonstrated how google glass can be used as a wearable device to publish Alfresco content using GDK - Glass Development Kit for this. After the session, we could try out the Google glass too! :)

On the whole, it was a great opportunity to see how people are using cutting edge technologies and customising Alfresco to change the way enterprises manage and interact with their documents.

If you miss this event, the recorded sessions will be available in Alfresco summit site and Youtube after some time, so it’s worth downloading and watching them.




Java Game Development - Part 2: Developing multi user game



Extending the game as multi-user application


When extending this game as multi-user game, another player baby fish is added to the game. In addition to escaping from enemy fish and meeting friendly fish, the baby fish players should compete with each other to go home sooner than the other while getting maximum number of points.

Design

Client - server architecture

Client server architecture is used instead of peer-to-peer approach to due to its simplicity and ease of development. 

In a client-server architecture all the game players (baby fishes), or "clients", are connected to a central machine, the Fish game server. 

The server is responsible for important decisions such as creating game friend/ enemy fish collection, managing state and broadcasting this information (x, y coordinates of players and non-players) to the individual clients. 

As a result, the server becomes a key bottleneck for both bandwidth and computations.
However, this approach will consume more network bandwidth. 



Concurrent game playing using multi-threading


Multi- threading approach is used to enable multiple users to play the game concurrently. A separate thread will represent each client.

Network Access using socket communication


TCP/ IP Socket communication (low level network communication) is used for two-way communication between server and clients. Remote Method Invocation (RMI) approach is not used here, as it will incur additional processing overhead.
Using encapsulation to support multiple network protocols

FishServer class and FishClient interface do not include any TCP/ IP networking specific programming. This generic design will support different network protocols with out changing the core game logic. 

Class Diagram


 Sequence Diagram


Implementation

Threading in Java

Synchronized keyword

Since game server is accepting different threads that request or send messages, which access same resources (E.g., objects, variables), for preventing thread interference and memory consistency errors.

Runnable interface

Runnable interface is used to implement what each player client thread is supposed to do once executed.

Networking in Java

Serializable Interface

We need to send the game information such as game scores and player/ non-player x, y coordinates across network.

To achieve the above, state of the objects is transmitted across network by converting objects to byte arrays.

Classes are serialized before sending through network and de-serialized once received using Serializable interface.

Socket and ServerSocket


ServerSocket object is created to listen for incoming game player client connections.
The accept method is used to wait for incoming connections. 

The accept method returns an instance of a Socket class, which represents the connection to the new client.

ObjectOutputStream/ ObjectInputStream methods (writeObject, readObject) are used to get object streams to reading from and writing to the new client. 

UI









 



Java Game Development - Part 1: Developing a single user game using strategy design pattern

Introduction


The Game

The lost fish is a simple educational game for children to learn about behaviors and characteristics of different sea creatures such as fishes and plants in a fun and challenging way.

E.g., Dolphin is an innocent, friendly sea animal, whereas shark is harmful

Also, it is intended to make the children aware of common characteristics of the sea creatures, which belongs to a particular category.

E.g., harmful animals will scream furiously and look angry

In this game, player is a baby fish that has lost in the sea. Baby fish has to find its way home passing different barriers, while escaping from harmful animals.

Game Rules


Assume, before starting the game, baby fish will be given some knowledge on the sea creatures by its mother fish. But, mother fish will not be able to tell about “all” the sea creatures.

If the baby fish collides with a harmful creature, the baby fish will get weak. (Loose energy)

If the baby fish identifies and meet friendly fish it will gain energy. If energy level is below zero, baby fish will die and the game is over.

Baby fish will get bonus points if it reach/find home soon.

Win the Game


Baby fish has to reach home with maximum energy level with maximum bonus points, to win the game.

Design

This game is designed with the intention of improving further with a variety of sea animals with different appearances and behaviors. Then, game will keep the players interested and also this will lead to a good learning resource as well.

Design Decisions

OOP concepts such as encapsulation, inheritance and polymorphism are used to improve the reusability, maintainability and the extendibility of the game.

 Strategy Design Pattern

Strategy design pattern is used to effectively extend the game with new sea creatures with diverse behaviors, to keep the player entertained. Also, different behaviors can be dynamically invoked using this approach.

An example scenario is given below:

Assume we have to add two new sea animals (E.g., whale and jelly fish) with different/ existing sound behaviors to the game, with out doing major changes to the core game design and avoiding duplicate code. If we use the traditional inheritance approach, where all the sea animal behaviors (E.g., sound/ scream) inherit from parent class SeaAnimal, then the code will be duplicated for similar behaviors. But, the given approach will solve that problem using interface implementations for similar behaviors.

The current design supports the above scenario in two different ways.
•    Inheritance: New sea creatures can be created by extending “SeaAnimal” abstract class
•    Polymorphism: Novel sound behaviors can be added or existing sound behaviors can be reused using “Sound” interface.

Using Constants

Constant values are used wherever applicable to improve reusability and maintainability.

Class Diagram


Sequence diagrams






 UI Design


Here's the video: https://www.youtube.com/watch?v=ipv_6yYAUw4

References

[1] http://obviam.net/index.php/design-in-game-entities-object-composition-strategies-part-1/
-->



Tuesday, July 29, 2014

"Updating Maven Project". Unsupported IClasspathEntry kind=4

To fix the issue,

  1. Right click on the project
  2. Maven > Remove maven nature
  3. Right click on the project
  4. Run as > Run configurations
  5. eclipse : clean
  6. Right click on the project
  7. Maven > Convert to maven projects

Friday, July 25, 2014

Apache Tomcat 7 displays blank page Mac OSX 10.9

After installing Apache Tomcat 7 using the following excellent tutorial,
http://wolfpaulus.com/jounal/mac/tomcat7/, the default page in http://localhost:8080 returned a blank page.

There can be several reasons that is causing this issue, and mine got fixed when I changed the default Tomcat port from 8080 to 8081 (It can be any available port) following http://www.mkyong.com/tomcat/how-to-change-tomcat-default-port/

To check the availability of ports and verify Tomcat is running in 8081, use the following command:
netstat -anf inet

The required change to change the port (In /conf/server.xml) in given below:

  port="8181" protocol="HTTP/1.1" 
               connectionTimeout="20000" 
               redirectPort="8443" />

Monday, May 19, 2014

org.alfresco.service.cmr.dictionary.DictionaryException: Could not import bootstrap model XXX.xml

To solve the above issue, check for typo/ syntax issues in model.xml

Error creating bean with name 'XXX' defined in class path resource [XXX/context/service-context.xml]: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Class {XXX}XXX has not been defined in the data dictionary

I got the above error while adding custom behavior related to custom aspect using AMP (Alfresco Module Package) with Alfresco Maven SDK.

This is how I resolved that:

Each module requires a module context file (module-context.xml). This loads the Spring configuration for the module. 

Custom content models can be bootstrapped into the repository via Spring configuration added to the module context file.

You need to either import your custom-model-context.xml here or directly define the bean configuration for the custom model here as given below. 

  

References:

Module context file:http://docs.alfresco.com/4.2/index.jsp?topic=%2Fcom.alfresco.enterprise.doc%2Fconcepts%2Fdev-extensions-modules-module-context.html

Adding module data:
http://docs.alfresco.com/4.2/index.jsp?topic=%2Fcom.alfresco.enterprise.doc%2Fconcepts%2Fdev-extensions-modules-custom-model.html


Monday, April 14, 2014

How to show Sinhala characters in Mac OS X Terminal?

 
UTF-7 is the character encoding that represents Sinhala text.

    • Terminal > Preferences > Settings > Advanced 
    • International
    • Set Character encoding as Unicode (UTF-7)

    Tuesday, April 8, 2014

    Basic SOLR concepts explained with a simple use case

    This is an example scenario to understand the basic concepts behind SOLR/ Lucene indexing and search using advertising web site[4].

    Use case:

    Searcher: I want to search cars by different aspects such as car model, location, transmission, special features etc. Also, I want to see the similar cars that belong to same model as recommendations.

    SOLR uses index which is an optimized data structure for fast retrieval.

    To create an index, we need to come up with a set of documents with fields in it. How do we create a document for the following advertisement?



    Title: Toyota Rav4 for sale
    Category: Jeeps
    Location: Seeduwa
    Model: Toyota Rav4
    Transmission: Automatic
    Description: find later


    SOLR document:


    document 1

    Toyota Rav4 for sale


    Jeeps
    Seeduwa
    Toyota Rav4
    Automatic
    Brought Brand New By Toyota Lanka-Toyota Rav4 ACA21, YOM-2003, HG-XXXX Auto, done approx 79,500 Km excellent condition, Full Option, Alloy Wheels, Hood Railings,
    call No brokers please.


    Some more documents based on advertisements...

    document 2

    Nissan March for sale

    Cars
    Dankotuwa
    K11
    Automatic
    A/C, P/S, P/W, Center locking, registered year 1998, full option, Auto, New battery, Alloys, 4 doors, Home used car, Mint condition, Negotiable,

    document 3

    Nissan March K12 for rent
    Cars
    Galle
    K12
    Automatic
    A/C, P/S, P/W, Center locking, registered year 2004, full option, Auto, New battery, Alloys, 4 doors, cup holder, Doctor used car, Mint condition, Negotiable,

    Inverted Index


    Then SOLR creates an inverted index as given below: (Lets take example field as Title)

    toyota doc1(1x)
    rav4 doc1(1x)
    sale doc1(1x) doc2(1x)
    nissan doc2(1x)
    march doc2(1x)

    1x means the term frequency of the document for that particular field.


    Lucene Analyzers


    Note that “for” term here is eliminated during Lucene stop word removal process using Lucene text analysers. You can come up with your own analyser based on your preference as well.

    Field configuration and search

    You can configure, which fields your documents can contain, and how those fields should be dealt with when adding documents to the index, or when querying those fields using schema.xml.

    For example, if you need to index description field as well and the description value of the field should be retrievable during search, what you need to do is add the following line in schema.xml [1].

    Now, assume a user search for a vehicle.

    Search query: “nissan cars for rent”

    SOLR query would be /solr/select/?q=title:”nissan cars for rent"

    Ok what about the other fields (Category, location, transmission etc. ?)?

    By default, SOLR standard query parser can only search one field. To use multiple fields such as title and description and give them a weight to consider during retrieval based on their significance (boosts) we should use Dismax parser [2, 3]. Simply said, using Dismax parser you can make title field more important than description field. 



    Anatomy of a SOLR query


    q - main search statement
    fl - fields to be returned
    wt - response writer (response format)

    http://localhost:8983/solr/select?q=*:*&wt=json
    - select all the advertisements

    http://localhost:8983/solr/select?q=*:*&fl=title,category,location,transmission&sort=title desc
    - select title,category,location,transmission and sort by title in descending order

    wt parameter = response writer
    http://localhost:8983/solr/select?q=*:*&wt=json - Display results in json format
    http://localhost:8983/solr/select?q=*:*&wt=xml - Display results in XML format

    http://localhost:8983/solr/select?q=category:cars&fl=title,category,location,transmission -
    Give results related to cars only

    more option can be found at [5].

    Coming up next...

    • Extending SOLR functionality using RequestHandlers and Components
    • SOLR more like this
    References:
    [1] http://wiki.apache.org/solr/SchemaXml
    [2] https://wiki.apache.org/solr/DisMax
    [3] http://searchhub.org//2010/05/23/whats-a-dismax/
    [4] Ikman.lk
    [5] http://wiki.apache.org/solr/CommonQueryParameters

    Wednesday, April 2, 2014

    How would you decide if a class should be abstract class or interface?

    It depends :)

    In my opinion, to implement methods in abstract class you need to inherit the abstract class.One of the key benefits of inheritance is to minimise the amount of duplicate code by implement common functionalities in parent classes. so if the abstract class have some common generic behaviour that can be shared with its concrete classes, then using abstract class would be optimal.

    However, if all methods are abstract and those methods do not represent any unique/significant behaviour related to  the class instances, it may be better to use interface instead.

    Use abstract classes to define planned inheritance hierarchies. Classes with already defined inheritance hierarchy can extend their behavior in terms of the “roles” they can play, which are not common to its parents all the other children, using interfaces. Abstract classes will not help in this situation because of multiple inheritance restriction in  java language.

    How interfaces avoid “Deadly Diamond of Death” problem?

    A key difference between interface and abstract class is, “Interfaces simulate multiple inheritance” for languages where multiple inheritance is not supported due to “Deadly Diamond of Death” problem.

    How interfaces avoid “Deadly Diamond of Death” problem?

    Since interface methods do not have their underlying implementation, unlike the inherited class methods, there won’t be this problem as there can be multiple method signatures that are same, but there can be only one implementation for a particular class instance as duplicate methods cannot be compiled without any errors.

    Reference:
    Head First Java

    Thursday, March 13, 2014

    Constructor() has private access in Class

    If it is obvious for you that this has nothing to do with an issue on granting access, check for version incompatibilities of the .class or the related class.

    package java.nio.file does not exist in Mac OSX

    This is new addition in java 1.7, so if by default JDK is set as older version, this exception will be given. However, when I check java -version and it says java version "1.7.0_45".

    If you have java version specific code in your maven application add the following section in your pom.xml
               

        

       
       










    Still it will give the following error:
    [ERROR] Failed to execute goal X.plugins:maven-compiler-plugin:2.5.1:compile (default-compile) on project X: Compilation failure
    [ERROR] Failure executing javac, but could not parse the error:
    [ERROR] javac: invalid target release: 1.7
    [ERROR] Usage: javac
    [ERROR] use -help for a list of possible options


    To solve this issue, set the JAVA_HOME variable to the following using any of the following methods:

    // Set JAVA_HOME for one session
    export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk/Contents/Home

    OR

    // Set JAVA_HOME for permanently
    vim ~/.bash_profile
    export JAVA_HOME=$(/usr/libexec/java_home)
    source .bash_profile
    echo $JAVA_HOME

    Now compile the application

    For those who are curious...

    When deciding which JVM to consider for compiling, path specified in JAVA_HOME is used. Here's how to check that.
    echo $JAVA_HOME

    If it is not specified in JAVA_HOME, using  the following command, you can see where JDK is located in your machine:
    which java

    It will give something like this: /usr/bin/java

    Try this to find where this command is heading to.
    ls -l /usr/bin/java

    This is a symbolic link to the path /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands

    Now try the following command:
    cd /System/Library/Frameworks/JavaVM.framework/Versions
    ls

    Check where "CurrentJDK" version is linked to. (Right click > Get info)
    Mine it was  /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents.

    Version specified as the "currentJDK" will determine which JVM should be used from the available JVMs.

    So, this is why I got the "package java.nio.file does not exist" at the first place, as the default referenced JDK is older than 1.7.

    How to point Current JDK to correct version?

    cd /System/Library/Frameworks/JavaVM.framework/Versions
    sudo rm CurrentJDK
    sudo ln -s /Library/Java/JavaVirtualMachines/jdk1.7.0_21.jdk/Contents/ CurrentJDK

    Additional info...

    Also, use the following command to verify from where the Java -version is read. (for fun!.. :))
    sudo dtrace -n 'syscall::posix_spawn:entry { trace(copyinstr(arg1)); }' -c "/usr/bin/java -version"

    It will output something like this:
    dtrace: description 'syscall::posix_spawn:entry ' matched 1 probe
    dtrace: pid 7584 has exited
    CPU     ID                    FUNCTION:NAME
      2    629                posix_spawn:entry   /Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk/Contents/Home/bin/java



    Saturday, February 22, 2014

    Named Entity Recognition using Conditional Random Fields (CRF)

    Named Entity Recognition

    Name Entity Recognition (NER) is a significant method for extracting structured information from unstructured text and organize information in a semantically accurate form for further inference and decision making.

    NER has been a key pre-processing step for most of the natural language processing applications such as information extraction, machine translation, information retrieval, topic detection, text summarization and automatic question answering tasks.

    In NER tasks frequently detected entities are Person, Location, Organization, Time, Currency , Percentage, Phone number, and ISBN.

    E.g., When translating "Sinhala text to English text", we need to figure out what are person names, locations in that text, so that we can avoid the overhead of finding corresponding English meaning for them. This is also helpful in question answering scenarios such as "Where Enrique was born?"

    Different methods such as rule based systems, statistical and gazetteers have been used in NER task, however, statistical approaches have been more prominent and other methods are used to refine the results as post processing mechanism.

    In computational statistics, NER has been identified as sequence labeling task and Conditional Random Fields (CRF ) has been successfully used to implement this.

    In this article I will use CRF++ to explain how to implement a named entity recognizer using a simple example.

    Consider the following input sentence:
    "Enrique was born in Spain"

    Now, by looking at this sentence any human can understand that Spain is a Location. But machines are unable to do so without previous learning.

    So, to learn the computer we need to identify a set of features that links the aspects of what we observe in this sentence with the class we want to predict, which in this case "Location". How can we do that?

    Considering the token/ word "Spain" itself is not sufficient to decide that it is a location in a generic manner. So, we consider its "context" as well which includes the previous/ next word, it's POS tag, previous NE tag etc. to infer the NE tag for token "Spain".

    Feature Template  and Training dataset

    In this example, I will use "previous word" as the feature. So, we will define this in feature template as given below:

    # Unigram
    U00:%x[-1,0]

    # Bigram
    B

    U00 is unique id to identify the feature. 

    I will explain %x[row, column]  using the following sentence that we going to train the model.
    I live in Colombo

    First, we need to define the sentence according to the following format. (training.data)
    I O
    live O
    in O
    Colombo Location

    current word: Colombo
    -1: in
    0: first column (Here, I have given only one column. But new columns are added when we define more features such as POS tag)
    In the above training file last column refers to the answers we give to model NE task.

    So, this feature indicates the model that after the word "in", it is "likely" to find a "Location".
    Now we train the model:

    crf_learn template train.data model

    Model file is generated using feature template and the training data file.

    Inference

    Now we need to know if the following sentence has any important entities such as Location.
    "Enrique was born in Spain"

    We need to format input file also according to the above format. (test.data)
    Enrique
    was
    born
    in
    Spain

    Now we use the following command to test the model.

    crf_test  -m model test.data

    Outcome would be the following:

    Enrique O
    was O
    born O
    in O
    Spain Location

    Likewise, the model will give predictions on entities present in the input files based on the given features and available training data.

    Note: Check the Unicode compatibility for different languages. E.g., for Sinhala Language it's UTF-7.

    Coming up next...
    • Probabilistic Graphic Models
    • Conditional Probability 
    • Finite State Automata
    • First order markov independence assumption

    Source code:
    https://bitbucket.org/jaywith/sinhala-named-entity-recognition

    Jayani Withanawasam

    Sunday, February 2, 2014

    Better approach to load resources using relative paths in Java

    FileInputStream (Absolute path)


    To load a resource file such as x.properties for program use, first thing that we would consider will be specifying the absolute file path as given below:

    InputStream input = new FileInputStream("/Users/jwithanawasam/some_dir/src/main/resources/
    config.properties”);

    However, when ever we moved the project to another location, this path has to be changed, which is not acceptable.

    FileInputStream (Relative path)


    So, the next option would be to use the relative file path as given below, instead of giving absolute file path:

    InputStream input = new FileInputStream("src/main/resources/config.properties”);

    This approach seems to solve the above mentioned concern.

    However, problem with this is the relative path is depending on the current working directory, which JVM is started. In this scenario, it is "/Users/jwithanawasam/some_dir". But, in a different deployment setting this may change, which leads to change the given relative path accordingly. Moreover, we, as developers do not have much control over JVMs current working directory.


    In any of the above cases, we will get java.io.FileNotFoundException error, which is a familiar exception for most java developers.


    class.getResourceAsStream


    At runtime, JVM checks the class path to locate any user defined  classes and packages. (In Maven, build artifacts and dependancies are stored under path given for M2_REPO class path variable. E.g., /Users/jwithanawasam/.m2/repository) The .jar file which is the deployable unit of the project will be located here.

    JVM uses class loader to load java libraries specified in class path.

    So, best thing we can do is load the resource specifying a path relative to its class path using class loader. Here, specified relative path will work  irrespective of the actual disk location the package is deployed.

    Following methods reads the file using class loader.

    InputStream input = Test.class.getResourceAsStream("/config.properties");

    Usually, in Java projects resources such as configuration files, images etc. are located in src/main/resources/ path. So, if we add a resource immediately inside this folder, during packaging, the file will be located in the immediate folder in .jar file.

    We can verify this using the following command to extract content of jar file:

    jar xf someproject.jar

    If you place the resources in another sub folder, then you have to specify the path relative to src/main/resources/ path.

    So, using this approach we can load resources using relative paths in a hard disk location independent manner. Once we package the application, it is ready to be deployed anywhere, as it it is, without the overhead of having to validate resource file paths, thus improving the portability of the application.

    ServletContext.getResourceAsStream for web applications


    For web applications, use the following method:

    ServletContext context = getServletContext();
        InputStream is = context.getResourceAsStream("/filename.txt");
     
    Here, file path is taken relative to your web application folder. (The unzipped version of the .war file)
    E.g., mywebapplication.war (unzipped) will have a hierarchy similar to the following.  
     
    mywebapplication
        META-INF
        WEB-INF
            classes
       filename.txt
     
    So, "/" means the root of this web application folder.  
    This method allows servlet containers to make a resource available to a servlet from any location, without using a class loader. 
    
    
    
    
     

    Wednesday, January 29, 2014

    Eclipse F5, F6 keyboard shortcuts do not work in Mac OSX?

    Option 1
    Use F5, F6 with fn key

    Option 2
    Mac > System Preferences > Keyboard > Keyboard > check "Use all F1, F2 etc. keys as standard function keys


    Friday, January 24, 2014

    How to synchronize Mac notes with Google/ Yahoo email account?

    •  Launch Mac notes application

    • Notes > Add account


    • Give email information


    • Select Notes

    • Click done.  You can move your notes to different sections to synchronize them with email accounts.
    • Now login to email account and check the "Notes" section (Lable in Google accounts).




    How to open two Eclipse instances in Mac


    Saturday, January 11, 2014

    Improve your Maths skills for artificial intelligence

    I want to pursue "Artificial Intelligence" as my future career. So, was thinking of a way improve my maths skills. Then I found this awesome site!

    https://www.khanacademy.org

    Khan academy will first give you are maths pretest to assess your skills. Based on that you will achieve some points. And then you got to do the other organized set or questions one by one. If you stuck in some question, then they will give you a  hint. If that does not work, there is a video demo for you to learn the area related to that question.

    I find it very effective way to learn, so try this out!

    Thank you so much Khan Academy, Good work!!!! :)

    Thursday, January 9, 2014

    How to add a file in local file system to SVN repository?

    Assume you have folder named "foldername" in your local file system and you need add that folder with its content to SVN repository.

    Following operation is a client side operation and it won't have any impact on the server:
    svn add foldername

    Once you commit files using following command, files, folders within the given folder will be added to the repository:
    svn commit foldername

    You can do both of the above given commands in one step using "svn import" as well.

    Additional notes:

    if you want to get rid of commit message in svn.commit.tmp, use the following command:
    svn commit Sensefy -F svn-commit.tmp

    If you get the following error:
    svn: Commit failed (details follow):
    svn: Could not use external editor to fetch log message; consider setting the $SVN_EDITOR environment variable or using the --message (-m) or --file (-F) options
    svn: None of the environment variables SVN_EDITOR, VISUAL or EDITOR are set, and no 'editor-cmd' run-time configuration option was found

    use following command to set vi editor as default editor.
    export SVN_EDITOR=vim