jsp interview questions
The basic concept of the Inversion of Control pattern (also known as dependency injection) is that you do not create your objects but describe how they should be created. You don’t directly connect your components and services together in code but describe which services are needed by which components in a configuration file. A container (in the case of the Spring framework, the IOC container) is then responsible for hooking it all up.
2. What are the different types of IOC (dependency injection) ?
There are three types of dependency injection:
- Constructor Injection (e.g. Pico container, Spring etc): Dependencies are provided as constructor parameters.
- Setter Injection (e.g. Spring): Dependencies are assigned through JavaBeans properties (ex: setter methods).
- Interface Injection (e.g. Avalon): Injection is done through an interface.
Note: Spring supports only Constructor and Setter Injection
3. What are the benefits of IOC (Dependency Injection)?
Benefits of IOC (Dependency Injection) are as follows:
Minimizes the amount of code in your application. With IOC containers you do not care about how services are created and how you get references to the ones you need. You can also easily add additional services by adding a new constructor or a setter method with little or no extra configuration.
Make your application more testable by not requiring any singletons or JNDI lookup mechanisms in your unit test cases. IOC containers make unit testing and switching implementations very easy by manually allowing you to inject your own objects into the object under test.
Loose coupling is promoted with minimal effort and least intrusive mechanism. The factory design pattern is more intrusive because components or services need to be requested explicitly whereas in IOC the dependency is injected into requesting piece of code. Also some containers promote the design to interfaces not to implementations design concept by encouraging managed objects to implement a well-defined service interface of your own.
IOC containers support eager instantiation and lazy loading of services. Containers also provide support for instantiation of managed objects, cyclical dependencies, life cycles management, and dependency resolution between managed objects etc.
4. What is Spring ?
Spring is an open source framework created to address the complexity of enterprise application development. One of the chief advantages of the Spring framework is its layered architecture, which allows you to be selective about which of its components you use while also providing a cohesive framework for J2EE application development.
5. What are the advantages of Spring framework?
The advantages of Spring are as follows:
- Spring has layered architecture. Use what you need and leave you don’t need now.
- Spring Enables POJO Programming. There is no behind the scene magic here. POJO programming enables continuous integration and testability.
- Dependency Injection and Inversion of Control Simplifies JDBC
- Open source and no vendor lock-in.
6. What are features of Spring ?
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.
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.
Spring supports Aspect oriented programming and enables cohesive development by separating application business logic from system services.
Spring contains and manages the life cycle and configuration of application objects.
Spring comes with 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. But other frameworks can be easily used instead of Spring MVC Framework.
Spring framework provides a generic abstraction layer for transaction management. This allowing the developer to add the pluggable transaction managers, and making it easy to demarcate transactions without dealing with low-level issues. Spring’s transaction support is not tied to J2EE environments and it can be also used in container less environments.
The JDBC abstraction layer of the Spring offers a meaningful exception hierarchy, which simplifies the error handling strategy. Integration with Hibernate, JDO, and iBATIS: Spring provides best Integration services with Hibernate, JDO and iBATIS
7. How many modules are there in Spring? What are they?
Spring comprises of seven modules. They are..
8. What are the types of Dependency Injection Spring supports?>
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9. What is Bean Factory ?
A BeanFactory is like a factory class that contains a collection of beans. The BeanFactory holds Bean Definitions of multiple beans within itself and then instantiates the bean whenever asked for by clients.
- BeanFactory is able to create associations between collaborating objects as they are instantiated. This removes the burden of configuration from bean itself and the beans client.
- BeanFactory also takes part in the life cycle of a bean, making calls to custom initialization and destruction methods.
10. What is Application Context?
A bean factory is fine to simple applications, but to take advantage of the full power of the Spring framework, you may want to move up to Springs more advanced container, the application context. On the surface, an application context is same as a bean factory.Both load bean definitions, wire beans together, and dispense beans upon request. But it also provides:
- A means for resolving text messages, including support for internationalization.
- A generic way to load file resources.
- Events to beans that are registered as listeners.
11. What is the difference between Bean Factory and Application Context ?
On the surface, an application context is same as a bean factory. But application context offers much more..