Spring Interview Questions Part: 1

  • What is mean by Dependency Injection? Or What do you mean by Inversion of Control?

Dependency injection (DI) is a programming design pattern and architectural model, sometimes also referred to as inversion of control or IOC, although technically speaking, dependency injection specifically refers to an implementation of a particular form of IOC.

Dependancy Injection describes the situation where one object uses a second object to provide a particular capacity. For example, being passed a database connection as an argument to the constructor instead of creating one internally. The term "Dependency injection" is a misnomer, since it is not a dependency that is injected, rather it is a provider of some capability or resource that is injected. There are three common forms of dependency injection: setter-, constructor- and interface-based injection.

Dependency injection is a way to achieve loose coupling. Inversion of control (IOC) relates to the way in which an object obtains references to its dependencies. This is often done by a lookup method. The advantage of inversion of control is that it decouples objects from specific lookup mechanisms and implementations of the objects it depends on. As a result, more flexibility is obtained for production applications as well as for testing.

  • What are the modules in Spring?
  1. The core container:

    The core container provides the fundamental functionality of the Spring framework. In this module primary component is the BeanFactory, an implementation of the Factory pattern. The BeanFactoryapplies the Inversion of Control (IOC) pattern to separate an application’s configuration and dependency specification from the actual application code.

  2. Spring context module :

    TThe Spring context is a configuration file that provides context information to the Spring framework. The Spring context includes enterprise services such as e-mail, JNDI, EJB, internalization, validation, scheduling and applications lifecycle events. Also included is support for the integration with templating frameworks such as velocity.

  3. Spring AOP module:

    The Spring AOP module allows a software component to be decorated with additional behavior, through its configuration management feature. As a result you can easily AOP-enable any object managed by the Spring framework. The Spring AOP module provides transaction management services for objects in any Spring-based application. With Spring AOP you can incorporate declarative transaction management into your applications without relying on EJB components.

  4. Spring DAO module:

    The Spring DAO module provides a JDBC-abstraction layer that reduces the need to do tedious JDBC coding and parsing of database-vendor specific error codes. Also, the JDBC package provides a way to do programmatic as well as declarative transaction management, not only for classes implementing special interfaces, but for all your POJOs (plain old Java objects).

  5. Spring ORM module:

    : Spring provides integration with OR mapping tools like Hibernate, JDO and iBATIS. Spring transaction management supports each of these ORM frameworks as well as JDBC.

  6. Spring Web module:

    The Web context module provides basic web-oriented integration features builds on top of the application context module, providing contexts for Web-based applications. As a result, the Spring framework supports integration with Jakarta Struts. The Web module also eases the tasks of handling multi-part requests and binding request parameters to domain objects.

  7. Spring MVC framework module:

    Spring provides a pluggable MVC architecture. The users have a choice to use the web framework or continue to use their existing web framework. Spring separates the roles of the controller; the model object, the dispatcher and the handler object which makes it easier to customize them. Spring web framework is view agnostic and does not push the user to use only JSPs for the view. The user has the flexibility to use JSPs, XSLT, velocity templates etc to provide the view.

  • What is a BeanFactory and XMLBeanFactory?

Bean factory is a container. It configures, instantiates and manages a set of beans. These beans are collaborated with one another and have dependencies among themselves. The reflection of these dependencies are used in configuring data that is used by BeanFactory.

XMLBeanFactory is a bean factory that is loaded its beans from an XML file.

  • What are Inner Beans?

A bean inside another bean is known as Inner Bean. They are created and used on the fly, and can not be used outside the enclosing beans. The Id and scope attributes for inner beans are of no use.

  • What is DataAccessException?

DataAccessException is an unchecked RuntimeException. These type of exceptions are unforced by users to handle. This exception is used to handle the errors occurring when the details of the database access API in use, such as JDBC.

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A review of “Spring Web Flow 2 Web Development” book from Packt.

About Spring Web Flow

Spring Web Flow allowing us to represent the UI flow in (part of) a web application in a clear and simple way. It has several advantages:

  • The UI flow in a web application is clearly visible by looking at the corresponding web flow definition (typically in an XML file).
  • Web Flows can be designed to be self contained. This allows you to see a part of your application as a module and reuse it in multiple situations.
  • Web Flows can define any reasonable UI flow in a web application, always using the same consistent technique. You’re not forced into using specialized controllers for very particular situations.

About this book:

“Spring Web Flow 2 Web Development” by Markus Stäuble, Sven Lüppken (from Packt) is a very good book to start with Spring Web flow. I got a chance to go through this book and I thought of writing a small review about this book in my page.

Just like the main well known Spring books, this book is also approaching learning by doing a small project.  In the entire book we are developing a small project (bug tracking system) and through that we are trying to learn web flow.

The source code for the book can be download from HERE .
Publisher: Packt Publishing (March 20, 2009)
Language: English

star-rating

Authors: Markus Stäuble, Sven Lüppken

TO BUY THIS BOOK (Click on the Pic): 

Whats special in this Book?

  • The book is different in some cases like it does not only explain how to create flows with Spring Web Flow, but also shows the integration with other technologies like JavaServer Faces, EasyMock, Hibernate, Spring Security.
  • Explains web flow example project which is using so many other technologies, tools and frameworks like Maven/Ant, Eclipse/Netbeans IDE, Easymock, Apache Tiles etc etc.

Advantages:

  • More importantly it covers latest version and advantages of Spring Web Flow.
  • “Spring Web Flow 2 Web Development” is special in one case. They are started with the Installation and set-up of the whole environment. As a programmer it will help you very much. (although they are proving Code).
  • It starts from the very basics and moves on further.
  • Explains things with Maven/Ant, eclipse/Netbeans. This sounds very good.
  • This book explains the integration of Spring and Java Server Pages very clearly. And it  also explains the Spring web flow and Faces integration. This may consider an added advantage of this book.
  • Authors are given Class diagrams also for our reference in many framework class cases. This helps us to get a full idea about that class and the functionalities that provides.
  • It also also explains the essential modules of the complete Spring framework stack.
  • Given the complete configuration files and details of flows and others. This helps us to get the overall picture of the configurations.
  • Given so many reference links to follow. This also given at each specific parts of the book where that respective technology explains.
  • Explains Spring Java Script. It is really good to find some tutorial about that Library framework. Though it is coming through Spring Web Flow 2, a very few authors touches it in their books.
  • Another great advantage is it covers Spring Security. Gives us a chance to learn about this Library.
  • Apache Tiles integration and configuration is also covered although the book.
  • It also covers Unit testing of this Spring Web flow using EasyMock. This is really good point with respect to developers point of view.
  • It gives us an idea about running in the SpringSource dm Server (modular OSGi -Open Services Gateway initiative).

Disadvantages:

  • In the installation chapter we are coming across a lot of frameworks/tools. If you are a person who knows most of them then that chapter will be easy for you. Otherwise you need a bit more time to understand that.
  • Missing Spring IDE explanation.
  • Not much information about Spring basics. That’s seems to be Okay because they mentioned it as a book for the people who knows Spring.
  • The code mentioned in the book follows the same font. If they would have make the syntax/code highlighted/with some sort of separation  then that would have been great to read.
  • One basic thing about the formatting. Paragraphs are not JUSTIFIED. May be  that affects the code snippets. But surely this is making a bit bad look for the entire book in my view.

A really good Spring book from Packt! “Spring Web Flow 2 Web Development”

Spring Web Flow Book from Packt

If you know Spring Application Framework and keen to study its Web Strength specially its MVC and Web flow then this book will be a really better way for that. Packt published its latest book regarding one of the key member of Spring Family; “Spring Web Flow 2“.  It covers a lot many things like Spring Faces ( Specially its inegration with JSF), Spring Web Flow (With its very Latest version) and Spring Security…The key point about the book is, it describes everything, starting from the basics like Installing and configuring the web flow to its unit testing. 

Do visit the home of  this  book from Packt through this link. Click here

Find out the Table of contents here. You can also do a free download of one Chapter.

SpringSource Acquires G2One Inc (The company behind Groovy and Grails)

On November 11, 2008, SpringSource announced that it acquired G2One Inc Whats BIG in this? right? But once you hear more about the G2One then you will definitely get the importance of this acquiring. G2One is the company behind the popular  Groovy and Grails technologies. Groovy and Grails are the most popular application infrastructure solutions in the world. Groovy is one of the most popular alternative languages for the Java Virtual Machine (JVM), with more than 30,000 downloads per month.

More about Groovy and Grails from their Official Site:


Groovy dynamic language for the JVM

Groovy is a dynamic language for the Java Virtual Machine, that offers a flexible Java-like syntax all Java developers can learn in matter of hours, and provides features seen in other dynamic languages like Ruby, Python or Smalltalk. Groovy lets you leverage and protect your investments in developer skills, tooling or server software, while still allowing the creation of innovative software or business knowledge assets in the form of Domain-Specific Languages.

Grails agile web application framework

Grails is an advanced and innovative Web-application framework based on Groovy, and built on proven and performant Open Source bricks such as Spring, Hibernate, SiteMesh, Quartz, and Ajax libraries. Grails enables IT teams to establish fast development cycles through agile methodologies, to deliver quality applications in reduced amounts of time by applying principles like Convention over Configurationto simplify the development tasks and focusing on what really matters: the business of your users and the ease of use of the application you will deliver to them.

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