Spring Core and Context

Question 1

Which interface is used to create spring IOC container?

Answer 1

ApplicationContext. There are multiple implementations of ApplicationContext. One needs to choose based on their requirement.

Question 2

Which are common implementations of ApplicationContext

Answer 2

ClasspathXMLApplicationContext, FileSystemXmlApplicationContext, AnnoationConfigApplicationContext, XmlWebApplicationContext, AnnotationConfigWebApplicationContext.

Question 3

What are POJO objects called in Spring?

Answer 3

Beans

Question 4

Which are mandatory properties for defining a bean in spring xml?

Answer 4

Bean id or name, bean class are mandatory properties.

Question 5

Which xml tag is used to inject a dependency in spring bean?

Answer 5

is used to inject a bean.

Question 6

Which xml tag is used to inject dependency using constructor?

Answer 6

tag is used.

Question 7

What happens if there are two beans of same type and a class wants an instance of that bean?

Answer 7

Then spring will fail as it will get confused as to which bean needs to be injected. Then we need @Qualifier annotation.

Question 8

Which xml configuration needs to be enabled to start autowiring using annotation?

Answer 8

enables autowiring using annotation.
@Autowired, @PostConstruct, @PreDestroy,
@PersistanceContext (if avaiable, like hibernate), @PersistanceUnit (if available)

Question 9

Which ways are used to do some post processing once all dependencies have been injected?

Answer 9

@PostConstruct annotation or using InitializingBean interface or init-method property of tag in xml.

Question 10

Which ways are used to do some pre processing before the context is destroyed and bean is destroyed?

Answer 10

@PreDestroy annotation, DisposableBean interface or destroy-method property of tag in xml.

Question 11

When is pre destroy call made?

Answer 11

When the application context is closed.

Question 12

How many types of autowiring is supported?

Answer 12

ByType, ByName or Constructor

Question 13

Which is default autowiring type?

Answer 13

Default mode in java based autowiring is byType.

Question 14

Which is the super class of Spring ApplicationContext?

Answer 14

BeanFactory is super of ApplicationContext.

Question 15

What additional features of ApplicationContext?

Answer 15

It adds enterprise level features like Internationalization, etc.

Question 16

Which is default autowiring type?

Answer 16

Default mode in java based autowiring is byType.

Question 17

Which is the super class of Spring ApplicationContext?

Answer 17

BeanFactory is super of ApplicationContext

Question 18

What additional features of ApplicationContext?

Answer 18

It adds enterprise level features like Internationalization, etc.

Question 19

Lifecycle of Spring Bean

Answer 19

1) Initialize Bean
2) Set dependencies
3) Set Bean factory or ApplicationContext
4) Init method or Post Construct method
5) Bean is used in application
6) Container is destroyed
7) Pre Destroyed method is called

Question 20

In what order will pre destory method of beans be called?

Answer 20

TBA

Question 21

How to pass hard coded value in bean property?

Question 22

How to get bean from ApplicationContext?

Answer 22

ApplicationContext applicatioContext = new ClasspathXmlApplicationContext("");
Type type 
= (Type) applicationContext.getBean("byName");
Type bean = applicationContext.getBean("byName", Type.class);

Question 23

Inner bean

Answer 23

Useful if some bean creation should not be allowed from outside directly. It only should be created inside other bean.
…

Now if you try to create hostel bean from outside you will not be able to create it.

Question 24

Alias for a bean

Question 25

How to get bean from ApplicationContext?

Answer 25

ApplicationContext applicatioContext = new ClasspathXmlApplicationContext("");
Type type 
= (Type) applicationContext.getBean("byName");
Type bean = applicationContext.getBean("byName", Type.class);

Question 26

How to inject list in bean?

Answer 26

A

B

Question 27

Alias for a bean

Question 28

What is use of idref?

Answer 28

Id ref is useful when you want to inject name of bean in other bean. You could do it with value=”beanName” but that would not guarantee that a bean with the same name exists in container. While id ref performs that check and will fail at runtime if no such bean exists.

Question 29

How to inject map inside a bean?

Answer 29

adfas

asdfasd

Question 30

Which method is present in InitializingBean that is used to perform processing after dependencies are set?

Answer 30

afterPropertiesSet() method

Question 31

Which method is present in DisposableBean that is used to perform processing before a bean is destoryed?

Answer 31

destroy() method

Question 32

Which scope is used to create a new bean instance everytime a dependency is injected?

Answer 32

Prototype

Question 33

What will happen if A bean is of singleton scope and its dependency B is of prototype scope?

Answer 33

Even though B bean is of prototype scope, it will not be created more than once for A. Because A is of singleton scope and only one instance of A is created.

Question 34

How to achieve A of singleton scope and its dependency B of prototype scope, and we want that every time we ask for A, a new instance of B should be injected in A?

Answer 34

Make dependency as proxy, so instead of B, a proxy of B is injected in A. So everytime we get bean A, proxy will have a new instance of B.

Question 35

How to load multiple bean files ?

Answer 35

Can achieve by using import tag and its property named as resource

Question 36

How to inherit a bean’s properties in another bean?

Answer 36

with the help of parent property of bean tag

Question 37

How to enable annotation based configuration?

Answer 37

context:annotation-config

Question 38

what is annotation?

Answer 38

Annotation is metadata information which direct compiler that is not part of program

Question 39

How to inject string value using annotation?

Answer 39

@Value

Question 40

How to enforce that a property of bean must be populated at configuration time?

Answer 40

@Required

Question 41

How to autowire bean if there is multiple same types of bean available?

Answer 41

1) @Resource(name=”nameofbean”)

2) @Autowire + @Qualifier(name=”nameofbean”)

Question 42

How to enable auto-discovery of a given bean?

Answer 42

context:component-scan.it is a superset of context:annotation-config

Question 43

what are the various ways through which we can annotating bean for autodiscovery

Answer 43

@Component,@Controller
@Repository
@Service