4.Spring IoC : Dependency Injection

The process of injecting the data from xml to Bean Class Object.

For Example

· we have a Student Bean, it has “Name” as String data member

· In xml we will place Name value as “Satya Kaveti”

· While loading the xml by the Spring Container it will wire the xml data with Bean Object

We have following data types

Primitive Data type : int, String, float

Secondary Data type : Objects, Class objects

Collections : List, set, Map

In Spring Dependency Injection can do in 2 ways

· Setter Injection

§ If we not pass any data through <property name=” ” value=” ”> the container will create def. constructor

§ Setter method values can pass by using value attribute or <value > child tag

<beans>

</bean>

</beans>

§ we should not pass duplicate attribute values

<property name="message" value="Hello Spring!!" /> X

<property name="message" value="Hello Spring!!" /> x

§ we must pass name attribute

<property name="message"

· Constructor Injection

we don’t have name attribute, we have to pass type – value – index if needed
you must pass Constructor arg, if our Bean contains parameterized constructor
If not pass arg const. it won’t create even def. Constructor
we won’t pass same type of Constructor with same data
If u have overloading Constructor (same no args –diiff type) u can solve by using Type attribute
we can pass more than one value using this, but it's not possible in setter
It any ambiguity in data type it will solve by order of Constructor
Constructor with more no.of params we will use INDEX attribute.
Overriding of index value can possible by const injection

<beans>

<constrctor-arg value="" type="" index="">

</consttor>

</baen>

</beans>