Scala: Tail Recursion

Tail recursion is a basic but important concept in Functional programming. Recursive functions has always been a pain point for me. I would be eliminated out of several interview rounds if interviewers places emphasis on recursion. In Java world thankfully, most people I know hate recursion because when nesting goes too deep, it impacts the…

Understanding Java 8 Lambda final finally variable

I am a little late to the java 8 party and was trying to quickly get some hands on with lambdas and ran into an issue where I got the error message Variables used in lambda should be final or effectively final   . I know what final is but what is effectively final. Here…

How to set up Apache Storm on mac using brew

I am learning about Apache Storm and the guide had long and winding instructions on how to install Apache Storm.  I installed the single node using brew and it was a breeze. I did not had to spend time figuring out out if I was installing latest version. Pre-requisites: Make sure that you have ‘HomeBrew‘ installed. One…

Waffle : Windows Single Sign On

Last week, I was working on an application where I had to do LDAP authentication. My cmpany has been using a very old jar file that had the required code for authenticating and authorizing users. There were two problems for me. 1. I had to revisit the documentation on LDAP setting in Jboss 4 and…

4 ways to set up datasources in Jboss AS 7

Last year my company decided to move from JBoss 4.x/5.x to Jboss AS 7. We use Maven and IZPack plugin to create automated deployment to Jboss 4. As a part of IZPack plugin, we would write the install.xmls for various environment, which would help us deploy war files, log.xml, jars, properties file in respective folders….

Install Or Manage multiple versions of Java on OS X

A few weeks ago my Mac hard drive crashed and I had to get a new grad drive. As part of upgrade, I had to wipe my drive clean and install Yosemite. What I did not realize was that Apple had goofed up Java instlation on Mac, as result of which my IntelliJ idea compalained…

Restful Webservice in 7 Steps using Spring boot

Last week I was working on a new application which required me to build a web service to access it’s functionality. I decided to check out Spring 4 RestController. I was amazed at how far we have come from writing all the boiler template code, xmls etc for making a restful call. With Spring4 boot,…

A quick tutorial on SAAJ API

We ran into an issue last week. I had to call a third party web service that was built in PHP. Anyone who wokrs with Java will tell you that calling a web service is not more 15 minutes coding. You take the wsdl, run wsdl2Java command from Axis2 and start calling the service. Like…

Read / Write Excel file in Java using Apache POI

About a year or two ago I was working with finance team where they wanted to pull the credit card transactions for all the customer using various combinations. Ex – – Get the credit card txns for today or certain date. – Get the txns for customer who used Mastercard or Visa. However they wanted…

13 Most Common Java Keytool Keystore Commands

I was working on a project last month where I had to call a third-party web service. The third-party web service wanted me to add a SSL keystore and I struggled. I could have gone to my UNIX Admin and asked him to do this job but decided to learn about all about keystores. I…