Parallel & Distributed Computing

• Parallel computing      --> all processors have access to a shared memory. Shared memory can be used to exchange information between processors.
• Distributed computing --> each processor has its own private memory (distributed memory). Information is exchanged by passing messages between the processors

                a & b - Distributed computing

                c        - Parallel computing

Cloud Computiing

Cloud computing is internet based computing with shared computing resources that are virtualized and accessed as a service, through an API.The main Objective of cloud computing is to provide easy and scalable acess to computing resources and IT services and to share resources over the Internet without actually purchasing them.

Most cloud computing customers do not own the physical infrastructure. They usually rent usage from a third-party provider. Services in cloud computing infrastructure are delivered through common centers and built on servers. Clouds often operate as single points of access for all consumers' computing needs. There are three main characteristics which distinguish it from traditional hosting. Firstly the resources are consumed as a service and paid only for what is used like the traditional utility services. Then it is elastic which means a user can have as much or as little of a service as they want at any given time. Also the service is fully managed by the provider. So consumer needs to have only a personal computer and Internet access.

Public/ external, private/ internal , hybrid and community cloud are classifications of cloud computing. Several organizations with similar requirements can get together and establish a community cloud to share their infrastructure. You can get an idea about other clouds through the below diagram.

Amazon, Google, Microsoft are providing cloud computing services to the cloud.
Cloud computing concept is very essential for the future world. There the provider earn money by selling products. And also the client saves his/ her money as no need to purchase all needed infrastructure and services as we can burrow it for only the needed time.

Struts Vs Spring

Struts

It is an open source web application framework. It is used to design large scale applications promoting Model-View-Controller architecture. Framework consists of set of custom tag libraries that helps to build dynamic web applications.

Container first look for the web.xml file to determine what struts action servlets exists are. The container is responsible for mapping all the file request to the correct action Servlet. When a user made a request through a submitting a form then controller determines what action to be performed. Then it sends the relevant information to process using a action bean. Most of the struts applications have only one controller named ActionServlet. The key advantage of having a controller is its ability to control the flow of logic through the highly controlled, centralized points.

The one more responsibility of the controller is to check the struts.config.xml file to determine which module to be called upon an action request. Struts.config.xml file is a configuration file which stores mapping of actions.

Then data is processed in model. Struts provide the ActionForm and the Action classes which can be extended to create the model objects. After processed then data is passed to view. The view in struts framework is mainly a jsp page which is responsible for producing the output to the user.
Struts tag libraries are struts components helps us to integrate the struts framework within the project's logic. These struts tag libraries are used within the JSP page. This means that the controller and the model part can't make use of the tag library but instead use the struts class library for strut process control. Then the output is viewed to the user.

Spring

Spring is an open source application framework. It consists of modules such as MVC architecture, data access, transaction management, authentication and authorization, messaging testing and may more. The below diagram shows the seven major modules in spring framework.

Spring AOP -     To provide declarative enterprise services (declarative transaction management), To allow users to implement custom aspects, complementing their use of OOP with AOP

Spring ORM - The ORM package is related to the database access.

Spring Web - The Spring Web module is part of Spring’s web application development stack, which includes Spring MVC.

Spring DAO - support in Spring is primarily for standardizing the data access work using the technologies like JDBC, Hibernate or JDO.

Spring Web MVC -  This is the Module which provides the MVC implementations for the web applications.

Difference between Struts and Spring

refer : http://www.roseindia.net

JQuery

JQuery is a library consists of javascript functions. It reduces the javascript codes in an application as just need to call those functions included in the library.

First need to import the library before using it in the application.

   <script type="text/javascript" src="jquery.js"></script>

The below program hides the p tags when click the button. So this uses button click event.  

<html>
<head>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
  $("button").click(function(){
    $("p").hide();
  });
});
</script>
</head>
<body>
<h2>This is a heading</h2>
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
<button>Click me</button>
</body>
</html> 

Below are some other ways of using JQuery

$(this).hide()- hides current element
$("p").hide() - hides all paragraphs
$("p.test").hide() - hides all paragraphs withclass="test"
$("#test").hide() - hides the element withid="test"
 
$("[href]")  -select all elements with an href attribute. 
$("[href='#']") select all elements with an href value equal to "#".
$("[href!='#']") select all elements with an href attribute NOT equal to "#".
$("[href$='.jpg']") select all elements with an href attribute that ends with ".jpg".

the official web site   - http://jquery.com/
Can learn more on   http://www.w3schools.com/jquery/default.asp



 

Hibernate

Hibernate is an open source software written in java. It is a framework to map object oriented domain model to a  traditional relational database. It is an object relational mapping (ORM -programing technique for converting data between incompatible type systems in  object oriented programming languages).

It's primary feature is to map java classes to database tables. Mapping is accomplished through a xml file or java annotations. Also provide data retrieval and query facilities. To write queries against Hibernate data objects Hibernate has a language named Hibernate Query language (HQL) like SQL.

Hibernate can also be used in J2EE applications as well as standalone applications with servlets and EJB session beans.

You can refer http://www.hibernate.org for more information.
To learn Hibernate visit http://www.visualbuilder.com/java/hibernate/tutorial/