Tuesday, November 26, 2013

Top 10 Spring Interview Questions Answers J2EE

Spring framework interview questions is in rise on J2EE and core Java interviews,  As Spring is the best framework available for Java application development and now Spring IOC container and Spring MVC framework are used as de-facto framework for all new Java development. With this popularity interview questions from spring framework is top on any list of  core Java Interview questions. I thought to put together some spring interview questions and answers which has appeared on many Java and J2EE interviews and useful for practicing before appearing on any Java Job interview. This list of Spring interview questions and answers contains questions from Spring fundamentals e.g. Spring IOC anddependency InjectionSpring MVC framework, Spring Security, Spring AOP etc, because of length of this post I haven't included Spring interview questions from Spring JDBC and JMS which is also a popular topic in core Java and J2EE interviews. I suggest to prepare those as well. Any way these Spring questions are not very difficult and based on fundamentals e.g. What is default scope of Spring bean and mostly asked during first round or telephonic round of Java interview. Although you can find answers of these Spring interview questions by doing Google but I have also included some answers for quick reference. As I said Spring  and Spring MVC is fantastic Java framework and if you are not using it than start using it, these questions will give you some head start as well.


Top Spring Interview Questions and Answers

spring interview questions and answers J2EENow let’s start with questions, these Spring interview Questions are not very tricky or tough and based upon primary concepts of spring framework. If you are developing application using Spring framework than you may be, already familiar with many of these Java and Spring interview questions and answers. Nevertheless it’s a good recap before appearing to any Spring and Java interview.


Spring Security Interview questions Answer 
Some of the reader requested to provide Spring Security interview questions and answer, So i though to update this article with few of Spring security question I came across. Here are those:

How do you setup LDAP Authentication using Spring Security?
This is a very popular Spring Security interview question as Spring provides out of the box support to connect Windows Active directory for LDAP authentication and with few configuration in Spring config file you can have this feature enable. See How to perform LDAP authentication in Java using Spring Security for detailed code explanation and sample.

How do you control concurrent Active session using Spring Security?
Another Spring interview question which is based upon Out of box feature provided by Spring framework. You can easily control How many active session a user can have with a Java application by using Spring Security. See this spring security example of how to control concurrent session in Java and Spring for exact details.


Question1: What is IOC or inversion of control?
Answer: This Spring interview question is first step towards Spring framework and many interviewer starts Spring interview from this question. As the name implies Inversion of control means now we have inverted the control of creating the object from our own using new operator to container or framework. Now it’s the responsibility of container to create object as required. We maintain one xml file where we configure our components, services, all the classes and their property. We just need to mention which service is needed by which component and container will create the object for us. This concept is known as dependency injection because all object dependency (resources) is injected into it by framework.

Example:
 
        
 
In this example CreateNewStockAccont class contain getter and setter for newBid and container will instantiate newBid and set the value automatically when it is used. This whole process is also called wiring in Spring and by using annotation it can be done automatically by Spring, refereed as auto-wiring of bean in Spring.


Question 2: Explain Bean-LifeCycle.

interview questions on Spring framework
Ans: Spring framework is based on IOC so we call it as IOC container also So Spring beans reside inside the IOC container. Spring beans are nothing but Plain old java object (POJO).
Following steps explain their life cycle inside container.
1. Container will look the bean definition inside configuration file (e.g. bean.xml).
2 using reflection container will create the object and if any property is defined inside the bean definition then it will also be set.
3. If the bean implements the BeanNameAware interface, the factory calls setBeanName() passing the bean’s ID.
4. If the bean implements the BeanFactoryAwareinterface, the factory calls setBeanFactory(), passing an instance of itself.
5. If there are any BeanPostProcessors associated with the bean, their post- ProcessBeforeInitialization()methods will be called before the properties for the Bean are set.
6. If an init() method is specified for the bean, it will be called.
7. If the Bean class implements the DisposableBean interface, then the method destroy() will be called when the Application no longer needs the bean reference.
8. If the Bean definition in the Configuration file contains a 'destroy-method' attribute, then the corresponding method definition in the Bean class will be called.

Question 3: what is Bean Factory, have you used XMLBeanFactory?
Ans: BeanFactory is factory Pattern which is based on IOC design principles.it is used to make a clear separation between application configuration and dependency from actual code.
XmlBeanFactory is one of the implementation of bean Factory which we have used in our project.
org.springframework.beans.factory.xml.XmlBeanFactory is used to create bean instance defined in our xml file.
BeanFactory factory = new XmlBeanFactory(new FileInputStream("beans.xml"));
Or
ClassPathResource resorce = new ClassPathResource("beans.xml");
XmlBeanFactory factory = new XmlBeanFactory(resorce);

Question 4: What are the difference between BeanFactory and ApplicationContext in spring?
Answer : This one is very popular spring interview question and often asks in entry level interview. ApplicationContextis preferred way of using spring because of functionality provided by it and interviewer wanted to check whether you are familiar with it or not.

ApplicationContext.

BeanFactory
Here we can have more than one config files possible
In this only one config file or .xml file
Application contexts can publish events to beans that are registered as listeners
Doesn’t support.
Support internationalization (I18N) messages
It’s not
Support application life-cycle events, and validation.
Doesn’t support.
Support  many enterprise services such JNDI access, EJB integration, remoting
Doesn’t support.



Question 5: What are different modules in spring?
Answer : spring have seven core modules
1.      The Core container module
2.      Application context module
3.      AOP module (Aspect Oriented Programming)
4.      JDBC abstraction and DAO module
5.      O/R mapping integration module (Object/Relational)
6.      Web module
7.      MVC framework module

Question 6: What is difference between singleton and prototype bean?
spring questions answers
Ans: This is another popular spring interview questionsand an important concept to understand. Basically a bean has scopes which defines their existence on the application
Singleton: means single bean definition to a single object instance per Spring IOC container.
Prototype: means a single bean definition to any number of object instances.
Whatever beans we defined in spring framework are singleton beans. There is an attribute in bean tag named ‘singleton’ if specified true then bean becomes singleton and if set to false then the bean becomes a prototype bean. By default it is set to true. So, all the beans in spring framework are by default singleton beans.

  singleton=”false”
>
        
 



Question 7: What type of transaction Management Spring support?
Ans: This spring interview questions is little difficult as compared to previous questions just because transaction management is a complex concept and not every developer familiar with it. Transaction management is critical in any applications that will interact with the database. The application has to ensure that the data is consistent and the integrity of the data is maintained.  Two type of transaction management is supported by spring

1. Programmatic transaction management
2. Declarative transaction management.


Question 8: What is AOP?
Answer : The core construct of AOP is the aspect, which encapsulates behaviors affecting multiple classes into reusable modules. AOP is a programming technique that allows developer to modularize crosscutting concerns,  that cuts across the typical divisions of responsibility, such as logging and transaction management. Spring AOP, aspects are implemented using regular classes or regular classes annotated with the @Aspect annotation

Question 9: Explain Advice?
Answer: It’s an implementation of aspect; advice is inserted into an application at join points. Different types of advice include “around,” “before” and “after” advice

Question 10: What is joint Point and point cut?
Ans: This is not really a spring interview questions I would say an AOP one.  Similar to Object oriented programming, AOP is another popular programming concept which complements OOPS. Join point is an opportunity within code for which we can apply an aspect. In Spring AOP, a join point always represents a method execution.
Pointcut: a predicate that matches join points. A point cut is something that defines at what join-points an advice should be applied

These spring interview Questions and answers are not very difficult and focused on spring fundamentals rather than focusing on advanced feature of session management, spring security, authentication etc. we will cover of those question on some other interview article. I would also suggest that share some spring questions asked to you guys during interview and than I can put together those with there answers for quick reference of everybody.

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