srini's tech journal

DOM XMLHTTPRequest

2012-01-18T08:07:00.000-05:00

XMLHttpRequest ready states: 0, 1, 2, 3, 4 0 - The object has been created, but not initialized (the open method has not been called). 1 - A request has been opened, but the send method has not been called. 2 - The send method has been called. No data is available yet. 3 - Some data has been received; however, neither responseText nor responseBody is available. 4 - All the data has been received.

Project Sedna - Part 1

2012-01-13T20:34:00.001-05:00

- Identify and create the rvm we want to use # switch to Ruby 1.9.3 $ rvm 1.9.3 $ ruby -v ruby 1.9.3p0 (2011-...) $ rvm list [...snipped...] => ruby-1.9.3-p0 [ x86_64 ] # create a new gem set $ rvm gemset create sedna # switch to new gemset $ rvm 1.9.3@sedna $ rvm list gemsets [...snipped...] => ruby-1.9.3-p0@sedna ... # show that

Clojure basics - Protocols and Datatypes

2012-01-07T07:35:00.000-05:00

- Clojure's split and slurp IO functions are built on two abstractions, reading and writing. This means we can use them on variety of destination types, including files, URLs, sockets, and they can extended to new types. - The slurp function takes an input source, reads the contents, and returns it as a string. - The split function takes an output destination and a value, converts the value to a

ZeroMQ basics

2012-01-06T11:39:00.000-05:00

http://www.zeromq.org/ - How to type a Ø in mac: Option + Shift + O Philosophy - Programming is a science dressed up as art, because most of us don't understand the physics of software, and it's rarely if ever taught. The physics of software is not algorithms, data structures, languages and abstractions. These are just tools we make, use, throw away. The real physics of software is the physics

Clojure basics - State

2011-12-30T09:23:00.001-05:00

A state is the value of an identity at a point in time. Clojure provides four reference types: - Refs manage coordinated, synchronous changes to shared state. - Atoms manage uncoordinated, synchronous changes to shared state. - Agents manage asynchronous changes to shared state. - Vars manage thread-local state. References and Software Transactional Memory (STM) - Most objects in Clojure are

Clojure basics - Functional Programming

2011-12-28T14:28:00.002-05:00

- Functional programming leads to code that is easier to write, read, test and reuse. - For effective functional programming Clojure makes use of: # Pure functions: >> Programs should be built out of pure functions. >> A pure function has no side effects; that is, it does not depend on anything but its arguments, and its only influence on the outside world is through its return value. >>

Clojure basics - Sequences

2011-12-28T11:27:00.004-05:00

- In Clojure, all data structures can be accessed through a single abstraction: the sequence (or seq - pronounced "seek"). - A seq is a logical list. It is not tied to implementation details of a list. - Collections that can be viewed as seqs are called seq-able (pronounced "seek-a-bull") - Clojure's sequence library is a set of functions that can work with any seq-able. It includes functions to

Clojure basics

2011-12-16T14:29:00.004-05:00

- Under the covers, Clojure is Java. - Clojure's complete API is at http://clojure.org/api - Clojure is homoiconic, which is to say that Clojure code is composed of Clojure data. - Clojure uses prefix notation to evaluate functions, which include mathematical operators. - Clojure data structures are immutable. - defn defines functions. - def is like defn but more general. It can used to define

Erlang basics

2011-11-11T16:58:00.001-05:00

Clean code is when you look at a routine and it's pretty much what you expected. - Ward Cunningham - In Erlang shell, expressions have to be terminated with period followed by whitespace (line break, a space etc.) - Variable names must begin with a capital letter. - Erlang has no such thing as a null value. - Erlang is about programming for the right cases: you only program for what you know

RabbitMQ - AMQP

2011-11-01T15:01:00.004-04:00

- A producer is a user application that sends messages. - A queue is a buffer that stores messages. - A consumer is a user application that receives messages - An exchange on one side receives messages from producer and on the other side it pushes them to the queues. The rules for exactly what exchange should do with messages it receives is defined by exchange type. Exchange Types: direct,

RoR - App with MongoDB

2011-10-13T14:45:00.002-04:00

- rails new mdn -T --skip-active-record - # Add the dependencies for MongoMapper

Keep-up with concepts

2011-09-14T06:58:00.001-04:00

Big-endian Vs Little-endian: What is the difference? Which one is more widely used? IP addresses: IPv4 vs IPv6 CIDR (Classless Inter-Domain Routing): System of grouping IP addresses into prefixes for routing tables. BGP (Border Gateway Protocol): Used by routers to negotiate updates to their routing tables. NAT (Network Address Translation): Used by ports to allow multiple hosts to use an IP

Setting up Rails environment in Mac

2011-08-29T16:09:00.007-04:00

Uninstall MacPorts: So that ... Install Xcode: So that ... Fix OS X Named streams issue Set up your bash environment (.bashrc, .bash_profile) Install Homebrew: So that... Use homebrew to install git, macvim, wget, proctools, ack, ctags-exuberant, markdown git - version control wget - is a package for retrieving files using HTTP, HTTPS and FTP, the most widely-used Internet protocols. It

Rails open source contribution opportunities

2011-08-25T17:18:00.000-04:00

- gem to help with internationalization of rails applications? - fork and update rails-erd to work for mongo. ~

Monaco gems

2011-08-19T17:15:00.011-04:00

Application bson_ext C extensions to accelerate the Ruby BSON serialization. bundler Bundler manages an application's dependencies through its entire life across many machines systematically and repeatably. builder Builder provides a number of builder objects that make creating structured data (mainly XML) simple to do. carmenA simple collection of geographic names and abbreviations for

Working with Splunk

2011-08-11T16:16:00.001-04:00

Installation dir: /opt/splunk To start Splunk: /opt/splunk/bin/splunk start To use Splunk web interface: http:/srinidev:8080 For documentation go to: http://www.splunk.com/r/docs

Learning jQuery

2011-05-24T13:33:00.004-04:00

Book: jQuery: Novice to Ninja from Earle Castledine and Craig Sharkie jQuery - Each jQuery command is made up of four parts: the jQuery function (or its alias '$'), selectors, actions, and parameters. Example command: jQuery('p').css('color', 'blue'); Breakdown: selector: jQuery('p'); action: .css; parameters: ('color', 'blue')Which means: We've asked the selector to select all paragraph tags

Shared Services Dev Trail

2011-04-13T15:32:00.055-04:00

> project creation - rails new shared_services - # edit Gemfile - bundle install - rails generate rspec:install > version control - # create repository in GitHub - # update readme - # add and commit changes - # push to github and heroku > static pages - # create rspec tests for static pages - # create static pages for Home, Contact and About Us - # update routes to simplify links - # add style

RoR Sample App Trail

2011-03-15T13:37:00.004-04:00

- rails new sample_app -T - # why -T option? - cd sample_app - # edit Gemfile with righ sqllite version and Rspec - bundle install - rails generate rspec:install - # edit .gitignore file - git init - git add . - git commit -m "Initial commit" - # create git repository in github - git remote add origin git@github.com:username/sample_app.git - git push -u origin master - # edit readme file and save

RoR Demo App Trail

2011-03-14T13:41:00.022-04:00

- rails new demo_app - cd demo_app - vi Gemfile - git init - git add . - git status - git commit -m "Initial commit" - create repository in github - git remote add origin git@github.com:username/demo_app.git - git push origin master - vi README - git mv README README.markdown && git commit -am "Improved README" - git push - git status - rails generate scaffold User name:string email:string - rake

RoR First App Trail

2011-03-10T17:41:00.036-05:00

- ruby - rails new first_app - bundle install - bundle show - rails server - git config --global user.name "FN LN" - git config --global user.email email - cd first_app - git init - git add . - git status - git commit -m 'initial commit' - git log - git remote add origin git@github.com:username/first_app.git - git push -u origin master - git checkout -b modify_README - rm -rf apps - git

Ruby Install

2011-03-08T15:39:00.002-05:00

This is how I installed Ruby 1.9.2 from source on linux. - Download latest source from http://www.ruby-lang.org/en/downloads/ ------ ruby-1.9.2-p180.tar.gz will be downloaded - cd to the folder that has downloaded file - gzip -d ruby-1.9.2-p180.tar.gz - tar -xvf ruby-1.9.2-p180.tar - cd ruby-1.9.2-p180 - Make sure your user has sudo permissions or run the rest of these as root. - sudo ./

Ruby basics

2011-03-04T13:37:00.158-05:00

This whole notes is based on a Ruby tutorial in http://rubylearning.org by Satish Talim. - Ruby is a scripting language Features:- Free format: start writing your program from any line and column. - Case Sensitive - Comments: Start with # or in between =begin, =end. - Statement delimiters: Semi-colon (;) only needed if writing more than one statement in a line. A linefeed is treated like a

JVM Memory

2011-02-25T07:52:00.003-05:00

Heap and Non-heap Memory The JVM manages two kinds of memory: heap and non-heap memory, both created when it starts. Heap memory is the runtime data area from which the JVM allocates memory for all class instances and arrays. The heap may be of a fixed or variable size. The garbage collector is an automatic memory management system that reclaims heap memory for objects. Non-heap memory

Usage terms

2011-02-22T07:17:00.001-05:00

Syntactic sugar: Programmers use the term syntactic sugar to refer to special rules that let you write your code in a way that doesn't correspond to the normal rules but that is easier to remember how to do and looks better.

Startup and Shutdown oracle instance

2010-12-20T09:33:00.005-05:00

sh> su - oraclesh> export ORACLE_SID=MYDBsh> sqlplus /nologsql> connect / as sysdbasql> shutdown immediatesql> startup

HTML5

2010-12-13T16:56:00.007-05:00

Interesting updates going on with HTML5. Just finished reading "Dive into HTML5" by Mark Pligrim. Liked it.

Unicode and Character Sets

2010-12-06T05:43:00.002-05:00

Here is a good article on this.The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!) - by Joel Spolsky

SSH Tunneling

2010-11-17T10:27:00.010-05:00

Wikipedia says "Computer networks use a tunneling protocol when one network protocol (the delivery protocol) encapsulates a different payload protocol. By using tunneling one can (for example) carry a payload over an incompatible delivery-network, or provide a secure path through an untrusted network."Some good articles on tunneling.Tunneling protocol from WikipediaSSH Tunneling made easy by

Photo book printing

2010-09-29T15:41:00.009-04:00

Was looking for the best option to print a photo book for our Key West trip. Found this review to be very helpful.Who Makes The Best Photo Books? by Jason Dunn from "Digital Home Thoughts"

Modem to Router connection

2010-09-24T18:40:00.008-04:00

Had hard time setting up zone alarm router until I came across this article.http://en.kioskea.net/forum/affich-19114-motorola-2210-dsl-modem-with-wrt54g-linksys#17Most router settings are good but didn't get internet connection until I did the MAC cloning.--------------------------Updated the router configuration to work without MAC cloning. The problem is that some ISPs want to allocate a single

Find duplicate rows

2010-09-23T16:23:00.006-04:00

If you want to delete duplicate rows from TEST_TABLE table based on data in column DUPCOL.-- Find the information about duplicate entries firstselect dupcol, count(*) num_of_dupsfrom test_tablegroup by dupcolorder by num_of_dups desc;-- Now delete the duplicate entries leaving the latest entry for each one in table-- If we convert max(rowid) to min(rowid) we can keep the first of the duplicate

Installing JBossWS-CXF in JBoss

2010-08-27T16:23:00.009-04:00

Need to have JAVA_HOME set.Need to have ant installed.If you haven't installed JBoss yet, install it first. For this example, let's say we have jboss-5.1.0.GA installed in /usr/local dir.Steps:Download supported JBossWS-CXF stack that is compatible with JBoss we have. In this case, let's say that is jbossws-cxf-3.3.1.GA. If we choose the zip download, it is going to be jbossws-cxf-3.3.1.

MAC Address

2010-08-10T06:56:00.000-04:00

MAC - Media Access ControlA 6 byte IEEE MAC address shall conform to the format and characteristics ofhexadecimal representation per IEEE 802. See [IEEE802] for the hexadecimalrepresentation definition and additional information. The value format is xx-xxxx-xx-xx-xx, where each x represents a single hex character (0 through 9 and‘A’ through ‘F’ or ‘a’ through ‘f’). The uppercase hexadecimal

IPv4 vs IPv6

2010-08-10T06:50:00.002-04:00

An Internet Protocol (IP) version 4 address shall conform to the format andcharacteristics as defined by RFC 3986. See [RFC3986] for additional details.Typically, the address is represented in dot decimal notation (also known asdotted quad notation, i.e., nnn.nnn.nnn.nnn). Example below illustrates a few validinstances.A basic IPv4 address.171.70.222.82An IPv4 address in a URL.http://

SNMP Traps and NMS

2010-06-13T11:33:00.007-04:00

SNMP: Simple Network Management ProtocolNMS: Network Management SystemSNMP traps enable an agent to notify the management station of significant events by way of an unsolicited SNMP message.Understanding SNMP TrapsIf you have a systems installed at various customer sites and need to be monitored, the solution is to build an NMS that accepts SNMP traps from those systems and send notifications in

RPM Creation

2010-05-28T10:11:00.006-04:00

Here is a very good link that shows with example how to create an rpm.Tips:To build a noarch rpm, make sure spec file has "BuildArch: noarch"Newer rpmbuild expects keyword 'License' instead of 'Copyright'Sample RPM build process for Jboss 5------------------------------------------------------------------------Download jboss-5.1.0.GA.zipASSEMBLE_RPM_ROOT=/home/srini/

Where to put properties files in Glassfish v3.1?

2009-11-18T13:16:00.005-05:00

If you want the properties file should be visible to all applications deployed in the domain:- put it in ${domainBaseDir}/lib/classes. This is by default within the classpath, so the files in this directory will be accessible.* ${domainBaseDir} is typically like ${glassfishInstallDir}/domains/${appDomain}Where can I put a property file unique to my domain?If the properties file should be only

XSLT Fundamentals

2008-05-03T19:45:00.002-04:00

XSL consists of three parts: * XSLT - a language for transforming XML documents * XPath - a language for navigating in XML documents * XSL-FO - a language for formatting XML documentsXSLT is a language for transforming XML documents into XHTML documents or to other XML documents.XPath is a language for navigating in XML documents.

JavaScript Fundamentals

2008-01-25T10:32:00.000-05:00

JavaScript is case sensitive.Where to put the JavaSript?- Scripts to be executed when they are called, or when an event is triggered, go in the head section. When you place a script in the head section, you will ensure that the script is loaded before anyone uses it.- Scripts to be executed when the page loads go in the body section. When you place a script in the body section it generates the

Adobe Flex Builder

2008-01-07T09:08:00.001-05:00

Training on Monday Jan 07, 2008Flex builder only works with Eclipse 3.1 or later. Seems like other IDEs are not yet supported.To see the short cut keys in Eclipse Flex builder.Help --> Key Assist (Ctrl+Shift+L)Access levelspublic, private, protected, internalMost commonly used system events: creationComplete, initialize, showInvestigate embedded images.SVG images: Scalable Vector Graphics.Grid in

Spring Configuration

2007-12-31T17:35:00.000-05:00

Configuring AspectJ in Spring applicationWhen the application has a Spring-configured aspect, which is a AspectJ aspect, the application needs to run within an AspectJ-enabled JVM. The best way to AspectJ-enable a Java 5 JVM is to start it with the following JVM argument: -javaagent:/path/to/aspectjweaver.jarThis effectively tells the JVM to perform load-time weaving of any AspectJ aspects. To

Advanced Bean Wiring

2007-12-31T16:11:00.000-05:00

References: "Spring in Action" by Craig Walls: Advanced Bean Wiring - Chapter 3A look into how else we can configure Spring beyond basic wiring.Sub-beaningSub-beaning is commonly used to reduce the amount of XML required to declare aspects and transactions. To accommodate sub-beaning, the element provides two special attributes:- parent: The parent attribute is to what extends is to

Spring Messaging

2007-12-27T17:04:00.000-05:00

References: "Spring in Action" by Craig Walls: Spring Messaging - Chapter 10JMS- JMS is all about applications communicating with one another, just like other remoting options like RMI and Hessian/Burlap. However, it differs in how that communication happens. JMS provides Java applications with the option of communicating asynchronously.- There are two main concepts in JMS: message brokers and

Spring Questions

2007-12-27T11:56:00.000-05:00

Components of Spring? What's their purpose?Types of autowiring?Scoping options offered by Spring? What's the default?Bean attributes forDefining factory methodDefining init and destroy methodsFlavors of Spring AOP support

Managing Transactions

2007-12-11T18:54:00.000-05:00

References: "Spring in Action" by Craig Walls: Chapter 6ACID- Atomic: Atomicity ensures that all of the operations in the transaction happen or none of them happen- Consistent: Once the transaction ends, the system is left in a state that is consistent with the business that it models.- Isolated: Transactions should be isolated from each other, preventing concurrent reads and writes to the same

Accessing database (Using JPA)

2007-12-11T18:45:00.001-05:00

References: "Spring in Action" by Craig Walls: Chapter 5What's special about Spring's data access exceptions is that you don't have to catch them. They are all unchecked exceptions. Spring promotes the use of unchecked exceptions.The Template Method Pattern: A template method defines the skeleton of the process. In software terms, a template method delegates the implementation-specific portions

JPA Quick Reference

2007-12-04T10:17:00.000-05:00

JPA - Java Persistence APIJPA package - javax.presistence@Entity, @Column --> Annotations@Id --> Primary Key (GeneratedType.AUTO, IDENTITY, SEQUENCE, TABLE)EntityManager ---> has API to perform DDL and DML operations on EntitiesPersistenceContext ---manages---> EntityManager ---manages---> EntitiesPesistenceContext - Two types: Transaction scope, ExtendedDefault transaction type in JPA is JTA (

Advising beans

2007-10-31T17:45:00.000-04:00

References: "Spring in Action" by Craig Walls: Chapter 4In software development, functions that span multiple points of an application are called cross-cutting concerns. Typically, these cross-cutting concerns are conceptually separate from the application's business logic. Separating these cross-cutting concerns from the business logic is where aspect-oriented programming (AOP) goes to work.- DI

Basic bean wiring in Spring

2007-10-28T11:14:00.000-04:00

References: "Spring in Action" by Craig Walls: Chapter 2In a Spring-based application, your application objects (beans) will live within the Spring container. There is no single Spring container. Spring comes with several container implementations that can be categorized into two distinct types - Bean factories and Application contexts.Bean factories (org.springframework.beans.factory.BeanFactory

What is Spring?

2007-10-28T10:26:00.000-04:00

References: "Spring in Action" by Craig Walls: Chapter 1Spring- is a framework that helps you develop a loosely coupled application code.- is a lightweight dependency injection and aspect-oriented container and framework.- vital components are Dependency Injection (DI), Aspect Oriented Programming (AOP)Dependancy Injection (DI)Traditionally, each object is responsible for obtaining its own

JPA: Persistence Units

2007-10-24T15:46:00.000-04:00

- A persistence.xml file is used to manage one or more persistence units. Like web.xml for a servlet application and ejb-jar.xml for an EJB application, this persistence.xml is a must for an entity application to run.- The file persistence.xml exists to define the various persistence-units that are to be available for persistence using JPA. Each persistence-unit defines a set of

JPA: Operations on Entity Objects

2007-10-24T13:38:00.000-04:00

The following are the legal operations that can be performed on Entity objects with the help of EntityManager API.Persisting Entity Objects: persist(object)- Entity objects are like regular java objects until they become managed and made persistent by the EntityManager. The persist(entityObject) methods makes the entity persistent in the underlying database and managed within the persistence

JPA: The Query API (JPQL)

2007-10-24T13:30:00.000-04:00

Java Persistence Query Language (JPQL)- EntityManager serves as factory class for getting a reference to the Query objects. The query string that we specify for locating entity objects is called Java Persistent Query Language (JPQL).- The current version of the JPQL is 1.0 and it is more robust flexible and object-oriented than SQL.- The persistence engine will parse the query string, transform

JPA Exceptions

2007-10-24T13:29:00.001-04:00

Exceptions- Whenever the persist() method is called, the persistence engine will check for the existence of that object with the help of its unique identifier (which is represented in the form of primary key). If any duplicate object is found, then a run-time exception, EntityExistsException will be thrown.- A call to getSingleResult() will execute the query and returns a single row that matches

JPA Entities

2007-10-24T12:48:00.000-04:00

In JPA terms an entity refers to a persistent object which can be stored and retrieved from a persistent storage. Since entities form the heart of the JPA, they have some unique characteristics like persistability, identity and transactionability. The property of persistability deals with the storing and retrieving of entity from and to a persistent medium like database. Identity property is

Did you know?

2007-10-22T10:32:00.001-04:00

- Class initialization proceeds top to bottom, which means you have to be careful when defining the order of static blocks. Here is why.

volatile fields

2007-10-15T21:43:00.000-04:00

class Animator implements Runnable{ private boolean volatile stop = false; public void stop() stop= true; public void run() { while (!stop) { oneStep(); try { Thread.sleep(100); } catch ... } } private void oneStep() {...}}What happens if variable stop is not defined as volatile?- Typical compiler considers a one thread execution of the code and

Java Related Abbreviatoins

2007-10-15T21:09:00.001-04:00

JSR: Java Specification RequestNBR: Napkin Based RequirementsPOJO: Plain Old Java ObjectsJPI: Java Persistence APISOAP: Simple Object Access ProtocolAJAX: Asynchronous JavaScript And XML.XSL: EXtensible Stylesheet Language.

To be understood

2007-10-14T01:41:00.000-04:00

- Difference between Error and Exception?- Class initialization proceeds top to bottom.- Closures in Java (Possible Java 7 addition)javac.comgafter.blogspot.com- Aspect oriented programming- Wildcards in java 5- Lexical scope- volatile variables- Understand javadocs- namespaces- Scheme language- Executer patternJPA: dirty changes?- Diff between hibernate 2 vs 3.- iBATISUsing Hibernate to Persist

Java Persistence API

2007-10-11T16:38:00.000-04:00

JPA- Package: javax.persistence- Java Persistence API (JPA) provides POJO (Plain Old Java Object) standard and object relational mapping (OR mapping) for data persistence among applications. This API has borrowed many of the concepts and standards from leading persistence frameworks like Toplink (from Oracle) and Hibernate (from JBoss). One of the great benefits of JPA is that it is an

Remote debugging J2EE applications

2007-09-12T10:44:00.000-04:00

How to set-up remote debugging between application running in unix/linux and source code in windows environment (Eclipse IDE)? This is a two step process: 1. Set up the following JVM options and restart application server instance. Make sure the port (8001 in this example) is open. :JVMOption:-Xdebug -Xnoagent -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=n In

Interview Questions

2007-09-04T16:50:00.001-04:00

- What are the two basic ways in which classes that can be run as threads be defined?> By creating a sub-class of Thread or implementing a Runnable interface. Must implement the run() method in both cases.- What is the difference between list, set and map?> List interface provides support for ordered collection of objects.> Set interface provides support for unordered, unique collection of

J2SE 5.0 New Features

2007-09-04T13:23:00.000-04:00

J2SE(TM) 5.0 New FeaturesGeneric types have been widely anticipated by the Java Community and are now part of J2SE 5.0. One of the first places to see generic types in action is the Collections API. The user of a generified API has to simply declare the type used at compile type using the <> notation. No casts are needed and in this example trying to add a String object to an Integer typed

Ajax Fundamentals

2007-08-17T13:37:00.001-04:00

AJAX - Asynchronous JavaScript And XML.AJAX is based on JavaScript and HTTP requests.

What is Vitria?

2007-08-01T16:33:00.000-04:00

Vitria specializes in integration server software for enterprises. An integration server allows a company to mix packaged applications, custom software, and legacy programs across a network. Vitria competes with SeeBeyond, Tibco, webMethods, and others. . Vitria's leading product line is called BusinessWare. BusinessWare supports both message-bus and hub-and-spoke integration server models. The

BusinessWare Environments

2007-08-01T15:02:00.000-04:00

Design EnvironmentIn the design environment, the solution architect, business process modelers, and programers use the BusinessWare modeling tools to create graphical integration solutions. This environment, called the BME (Business Modeling Environment), allows you to develop and work with models that are visual representations of your solution that can be used through the entire solution