Autowiring in spring

Summary

• Autowiring is a mechanism in Spring that allows the framework to automatically detect and inject the dependent beans to the properties of the target bean without the need for explicit configuration.
• In simple words, when we apply autowiring, then Spring looks for the dependent beans in the container and automatically injects them into the target object.
• Benefits:
  • This can save a lot of time and effort, especially in large-scale applications where there are a large number of dependencies between objects.
• Drawbacks:
  • No control of the programmer.
  • It can't be used for primitive and not recommended for string values.

Syntax

`

<bean class="com.autowire.demo.beans.Account" id="account1" autowire-candidate="false">
    <property name="accountId" value="SV-101"/>
    <property name="balance" value="50000.0"/>
</bean>

<bean class="com.autowire.demo.beans.Account" id="account2">
    <property name="accountId" value="SV-102"/>
    <property name="balance" value="100000.0"/>
</bean>

<bean class="com.autowire.demo.beans.Customer" id="customer" autowire="byType">
    <property name="name" value="Neeraj"/>
</bean>

`

Conclusion

• By setting autowiring type to byName it will detect the dependant bean by name.
• If we have more than two beans of the same type then setting type to byName will throw exception NoUniqueBeanDefinitionException since spring will find multiple beans of the same type.
• To handle this and help Spring select a particular bean to be injected, we can set an attribute called autowire-candidate to false for all other beans.
• This means that for all the beans where an autowire-candidate is set to false, the Spring container will not consider them for autowiring.
• Possible values for autowire-candidate:
  • true: bean is candidate for autowiring.
  • false: bean is not a candidate for autowiring.
  • default: spring decides automatically which bean to inject.
• Note: If we don’t specify the autowire-candidate attribute, it defaults to true, meaning the bean will be considered for autowiring.
• Since account2 is set to false, therefore it will be ignored and another bean will be injected.