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="account">
    <property name="accountId" value="SV-101"/>
    <property name="balance" value="50000.0"/>
</bean>

<bean class="com.autowire.demo.beans.Address" id="address">
    <property name="houseNo" value="25"/>
    <property name="city" value="Bhopal"/>
</bean>

<bean class="com.autowire.demo.beans.Customer" id="customer" autowire="constructor">

</bean>

`

Conclusion

• Here, since for the last bean, no values are injected for Customer.
• Therefore, for constructor with 4 arguments, since no argument is passed so the default values for name will be null and age will be 0
• Spring will choose automatically which constructor to use out of two.
• But we can add following code to resolve ambiguity to call constructor having first argument as Account and second as Address.

`

<bean class="com.autowire.demo.beans.Customer" id="customer">
  <constructor-arg ref="account"/>
  <constructor-arg ref="address"/>
</bean>

`