Spring Framework Interview Questions And Answers - DoAnswers.com

Spring is a layered Java/J2EE application framework, based on code published in Expert One-on-One J2EE Design and Development by Rod Johnson (Wrox, 2002).

Spring includes:

1. The most complete lightweight container, providing centralized, automated configuration and wiring of your application objects. The container is non-invasive, capable of assembling a complex system from a set of loosely-coupled components (POJOs) in a consistent and transparent fashion. The container brings agility and leverage, and improves application testability and scalability by allowing software components to be first developed and tested in isolation, then scaled up for deployment in any environment (J2SE or J2EE).

2. A common abstraction layer for transaction management, allowing for pluggable transaction managers, and making it easy to demarcate transactions without dealing with low-level issues. Generic strategies for JTA and a single JDBC DataSource are included. In contrast to plain JTA or EJB CMT, Spring's transaction support is not tied to J2EE environments.

3. A JDBC abstraction layer that offers a meaningful exception hierarchy (no more pulling vendor codes out of SQLException), simplifies error handling, and greatly reduces the amount of code you'll need to write. You'll never need to write another finally block to use JDBC again. The JDBC-oriented exceptions comply to Spring's generic DAO exception hierarchy.

4. Integration with Toplink, Hibernate, JDO, and iBATIS SQL Maps: in terms of resource holders, DAO implementation support, and transaction strategies. First-class Hibernate support with lots of IoC convenience features, addressing many typical Hibernate integration issues. All of these comply to Spring's generic transaction and DAO exception hierarchies.

5. AOP functionality, fully integrated into Spring configuration management. You can AOP-enable any object managed by Spring, adding aspects such as declarative transaction management. With Spring, you can have declarative transaction management without EJB... even without JTA, if you're using a single database in Tomcat or another web container without JTA support.

6. A flexible MVC web application framework, built on core Spring functionality. This framework is highly configurable via strategy interfaces, and accommodates multiple view technologies like JSP, Velocity, Tiles, iText, and POI. Note that a Spring middle tier can easily be combined with a web tier based on any other web MVC framework, like Struts, WebWork, or Tapestry.

You can use all of Spring's functionality in any J2EE server, and most of it also in non-managed environments. A central focus of Spring is to allow for reusable business and data access objects that are not tied to specific J2EE services. Such objects can be reused across J2EE environments (web or EJB), standalone applications, test environments, etc without any hassle.

Spring's layered architecture gives you a lot of flexibility. All its functionality builds on lower levels. So you can e.g. use the JavaBeans configuration management without using the MVC framework or AOP support. But if you use the web MVC framework or AOP support, you'll find they build on the configuration framework, so you can apply your knowledge about it immediately.

1. The spring container finds the bean?s definition from the XML file and instantiates the bean.

2. Using the dependency injection, spring populates all of the properties as specified in the bean definition.

3. If the bean implements the BeanNameAware interface, the factory calls setBeanName() passing the bean?s ID.

4. If the bean implements the BeanFactoryAware interface, 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.

6. If an init-method is specified for the bean, it will be called.

7. Finally, if there are any BeanPostProcessors associated with the bean, their postProcessAfterInitialization() methods will be called.

Lightweight ? spring is lightweight when it comes to size and transparency. The basic version of spring framework is around 1MB. And the processing overhead is also very negligible.

Inversion of control (IoC) ? Loose coupling is achieved in spring using the technique Inversion of Control. The objects give their dependencies instead of creating or looking for dependent objects.

Aspect oriented (AOP) ? Spring supports Aspect oriented programming and enables cohesive development by separating application business logic from system services.

Container ? Spring contains and manages the life cycle and configuration of application objects.

Framework - Spring provides most of the intra functionality leaving rest of the coding to the developer.

The bean tag has two more important attributes with which you can define your own custom initialization and destroy methods. Here I have shown a small demonstration. Two new methods fooSetup and fooTeardown are to be added to your Foo class.

"http://www.springframework.org/dtd/spring-beans.dtd">

In the bean tag the id attribute specifies the bean name and the class attribute specifies the fully qualified class name.

JDBC can be used more efficiently with the help of a template class provided by spring framework called as JdbcTemplate.

9. What are important ApplicationContext implementations in spring framework?

ClassPathXmlApplicationContext ? This context loads a context definition from an XML file located in the class path, treating context definition files as class path resources.

FileSystemXmlApplicationContext ? This context loads a context definition from an XML file in the filesystem.

XmlWebApplicationContext ? This context loads the context definitions from an XML file contained within a web application.

When wiring beans, if a bean element is embedded to a property tag directly, then that bean is said to the Inner Bean. The drawback of this bean is that it cannot be reused anywhere else.