Senthil B Kumar

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since Feb 09, 2004
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Recent posts by Senthil B Kumar

I created a cookie in a java filter and added back to the response using response.addCookie() before returning to the client node.js application. This web application is accessed using a localhost URL in the browser. After reading about cookie domain issue while using 'localhost', i did not set any domain or path in the cookie, while creating it.

Now the Chrome or Firefox browsers don't show-up the cookie in the browser. All my URLs are http://localhost but, each page having different path.

Step 1: During a request to http://localhost/app/login cookie is created and set in the response
Step 2: When the page loads after response, no cookies are shown in Chrome
Step 3: During the next request http://localhost/app/customer the previously created cookie is not recieved when trying request.getCookies().
Step 4: Before returning back to client application, a cookie is created
Step 5: Now the cookie created in Step 4 is shown in Chrome
Step 6: The next request is also sent to http://localhost/app/customer , now the cookie created in step 4 is recieved in the server as well

If cookie creation for localhost is an issue, how does it work for Steps 4-6 only ?

How can i make the created cookie available to all paths under the localhost domain ? I tried using cookie.addPath("/") as mentioned in this post but, no change.

Note: Due to admin privilege issues in my development machine, i am not able to set-up a domain name to my localhost IP in etc/hosts file.

2 years ago
In a multi-channel supporting web application,

how can we detect and differentiate the user channel from which user request is coming from ?

By user channel, i mean it could be a thin client (web application) or thick client (native mobile app).

If it is a thin client, i can use 'user-agent' to identify and differentiate the browser from where the request was placed. But, how to distinguish between Thin and Thick client ?

Note: One approach we thought about is to use a custom Request Header but, then it could be easily faked by browser tools like firebug.
I am looking for a simple example/scenario explaining Buffer Overflow happening in JEE Web Application and how this specific scenario is prevented.

There could be N number of ways this could happen, I am just looking for any one example to help me to understand.

Note: I am having problem in visualizing a buffer overflow error in JEE based web application, that is the reason I am looking for a specific example.
2 years ago
While trying to understand the purpose of 'Spring Data' i came across this article and tried few examples with Gemfire/ Redis repositories and their corresponding Spring-Data components. Could someone help me with the following questions.

Scenario: When GemFire was my datastore, i had to use methods create, get and remove on the GemFireTemplate to perform the CRUD operations. When Redis was my datastore, I had to use methods .opsForHash().put , .opsForHash().get and .opsForHash().delete on the RedisTemplate to perform the same CRUD operations.


Isn't Spring-Data supposed to provide a level of abstraction to the underlying data store ? If i am expected to know the respective CRUD methods and have different APIs based on the underlying data store, what kind of abstraction does Spring-Data components bring in ? Can't I directly use a Jedis or Java client for Gemfire to perform these datatstore specific CRUD operations ?

This Article seems to explain that but, looks like i need some help in understanding it.

>> there is no general API to all the persistence stores. The differences are too fundamental. But the Spring Data project does provide a common programming model to access your data <<
3 years ago
I am trying to run this Spring Session example available here but, I've used Maven instead of Gradle. I get the following error both while a) Running the WAR file and b) Deploying the WAR in an WildFly8.2 server

A quick search suggests that the problem could be conflicting versions among various dependencies quoted in the pom.xml.

What is the root cause & solution for this error ?

Error while Running or Deploying the WAR


Here is my complete POM.xml

3 years ago
The source code of the project is available @

I haven't set-up Redis or written any detailed code for Redis. As per Spring Boot+Spring Session, an embedded Redis instance should have been started to which the Spring Session should have been persisted. but when i am running, the embedded Redis instance is not getting created.
3 years ago
I was trying to set-up this Spring-Session example using Spring Boot + Maven (the source in the GIT link is using Gradle).
There were no compilation error, the deploy-able WAR file also got generated using the repackage goal.

When trying to deploy the WAR file in my WildFly server, i get the following error related to Redis.
I do not have Redis server running in my machine (since i assume that an embedded Redis instance will be created as part of the application, even in an deployed WAR file)


Caused by:

Environment: WildFly8.2 running in Domain Mode (3 nodes running in Full-HA profile) Application: Spring Boot + Spring Session + Maven

Question: Is this error because an embedded Redis instance cannot be created while the WAR file is deployed to a container ?
I haven't tried running this as executable WAR file yet.

Complete Error Stack:

3 years ago
Can i manage the complete HTTPSession lifecycle (Creation, Update, Destroy and Expiry) only with Spring Session and without using Spring Security ?

Reason i got this question is that, Spring Security states that it provides 'Session Auto-Expiry' & 'Concurrent Session' features. Wouldn't 'Session Auto-Expiry' be available in 'Spring Session' itself ?
3 years ago
Spring documentation says that Spring Session can transparently leverage Redis to back a web application’s HttpSession when using REST endpoints.

Does anyone know if Spring supports GemFire in this place instead of Redis to back a web application's HttpSession ? I know there is a Spring-Data-Gemfire component that help us to use Spring Data to write to GemFire but, i want to write my SpringSession to GemFire.

3 years ago
One last question on this line, are there any differences between the Scala implementation & Java implementation in terms of the following attributes ?

1) Ease of adoption & learning curve.
2) Scalability & performance
3) Resiliency
4) Industry feedback and adoption rate.
5) Modularity and cloud readiness.
3 years ago
my recent read is all about building web applications with technologies moving away from monolithic architecture to micro-service based reactive & scalable applications.

With too many 'Jargons-Overload' and to bring some sanity to my thinking, I am trying to think out aloud by documenting my understandings and raising questions (however trivial/stupid it could be).

Please do share your thoughts/feedback/comments/amswers around these. Feel free to correct any of my incorrect understanding.

  • Spring MVC - to build RESTfull services (which will contain different business functionality implemented as multiple services
  • API Gateway - to validate calls to these RESTfull services (aka API calls) and to Orchestrate across multiple services/APIs
  • Servlet 3 (Async) - to build Asynchronous Server side (especially Servlets) code
  • RxJava - to build Asynchronous Server side code (can be tied with Spring MVC to provide Async feature)
  • Futures , Observables - No clarity yet. I am still reading
  • Play , Akka & Scala - A web framework, message driven run-time and programming language to develop reactive applications (meaning high performance, scalable & event driven)
  • WebSockets - to send messages to a server and receive event-driven responses without having to keep continuously polling the server for a reply
  • Node.js/Backbone.js - a) to utilize the RESTfull services built as Microservices b) Redirect updated Model/Data to multiple views for multiple user channels c) API gateway could also be built using this server side javascript

  • Question # 1 Could somebody help in putting together complete architecture picture of where, how all these technologies fit and/or compliment each other ? I will give a shot and update a picture later.

    Question # 2 Is the combination of Play, Akka & Scala equivalent and replacement to the combination of Spring MVC + Servlet 3 Async + RxJava ?

    Question # 3 If i use Node.js/Backbone.js , do they support the WebSockets functionality, or do i have to use a another library that could support it ? If so, for what purpose will i use WebSockets for ?

    Question # 4 How do I use Servlet 3 (Async) to build my micro-services ? Instead of writing plain Servlets in Servlet3.0 spec, should I use RxJava along with SpringMVC for this asynchronous feature ?

    Question # 5 If I can bring concurrency in Controler layer (Servlet/SpringMVC), how can I bring it in rest of the layers after it ? Else, would it truly give me the due advantage ?

    Question #6 What are Java Futures, Observables ? Are they components or Libraries used to implement the Message/Event driven architecture in my other layers ?

    Question #7 Where would Client-Side-MVC fit in this whole picture ? and what advantage it could offer in such a scenario ?
    Are there version of Play & Akka which supports plain Java programming language as well?
    3 years ago
    I understand that Typeface is a company that provides support for both Scala and Akka framework. Are these 2 different flavors of the Play framework or each are totally different framework for different purposes ?

    3 years ago
    Is Scala another scripting language or another framework like Struts/Spring.. etc ?

    What is the use case for Scala ?
    3 years ago