Auto wiring introduction with xml and annotation

-> it is used to inject dependencies automatically
-> it can't be used to inject primitive and string values, it works with reference only.

It can be done by two ways:

1)XML

2)ANNOTATION

With XML:

    Autowiring can be done in 

        a)byName

        b)byType

        c)constructor

        d)autodetect--It is deprecated since spring 3

With Annotations:

        a)Autowired

        b)Qualifier

                                 Autowiring of Bean in xml 

Object can be decleared in two ways:

This two are same: Either cast the bean or give the bean class:Emp emp = context.getBean("emp", Emp.class);

Emp emp = (Emp)context.getBean("emp);

"When using byName"

When giving the Autowired property to reference variable class.

The bean name and the object name should be similar

e.g

private Address address;

<bean class="some class" name="address"/> 

This both address should be same. it will not give error, but gives a null.

"When using byType"

There will be ambiguity problem. So better to use byName

When using byName and byType, setter injection is used where as when using constructor , constructor injection is used.

<bean class="com.mountech.autowire.Emp" name="emp" autowire="byName"/>

                             Auto Wiring with Annotation

->@Autowired can be used above property, setter and constructor. 3 ways of autowiring

->@Qualifier("address") is used to specify the name of the bean

@Autowired
@Qualifier("address")