Inner Beans inside Spring Framework

Use cases of inner beans:

• Inner beans is used to define and declare a bean within a scope of another bean.
• As a standard practice, when a bean is used for a particular purpose for one bean, then it is advised to use inner bean.
• It makes our code secure from outer world.

Important points:

• When a bean do not need to be shared by other beans, then it can be declared as inner bean.
• An inner bean cannot be used by other beans except enclosing bean.
• Inner beans does not require id attribute to access, but we can provide it for readability. Since spring will recognize the inner bean just by seeing the outer bean.

Syntax

`

<bean class="com.spring.demo.beans.com.autowire.demo.Customer" id="customer1">
    <property name="name" value="Sourav"/>
        <property name="account">
            <bean class="com.spring.demo.beans.com.autowire.demo.Account" id="account1">
                <property name="accountId" value="SAVINGS-ACC-101" />
                <property name="balance" value="400000" />
            </bean>
        </property>
</bean>

<bean class="com.spring.demo.beans.com.autowire.demo.Customer" id="customer2">
    <property name="name" value="Codey"/>
    <property name="account">
        <bean class="com.spring.demo.beans.com.autowire.demo.Account" id="account2">
            <property name="accountId" value="SAVINGS-ACC-102" />
            <property name="balance" value="500000" />
        </bean>
    </property>
</bean>

`

• Note:

• Here, we are declaring 2 outer beans for each outer bean.
• Outer bean is Customer class and Account is the inner bean.
• And for each inner Account bean, both can be accessed inside that outer bean and no other bean can access the Account bean.
• This ensures security for inner beans, and thereby implementing encapsulation of OOP's principle.