Auto-Wiring Beans Spring

In Spring, 5 Auto-wiring modes are supported

no – Default, no auto wiring, set it manually via “ref” attribute
byName – Auto wiring by property name. If the name of a bean is same as the name of other bean property, auto wire it.
byType – Auto wiring by property data type. If data type of a bean is compatible with the data type of other bean property, auto wire it.
constructor – byType mode in constructor argument.
autodetect – If a default constructor is found, use “autowired by constructor”; Otherwise, use “autowire by type”.

Customer and Person Bean Classes

public class Customer 
{
 private Person person;
 
 public Customer(Person person) {
  this.person = person;
 }
 
 public void setPerson(Person person) {
  this.person = person;
 }
 //...
}

public class Person 
{
 //...
}

1. Auto-Wiring ‘no’ 
This is the default mode, you need to wire your bean via ‘ref’ attribute.

2. Auto-Wiring ‘byName’ 
Auto-wire a bean by property name. In this case, since the name of “person” bean is same with the name of the “customer” bean’s property (“person”), so, Spring will auto wired it via setter method – “setPerson(Person person)“.

3. Auto-Wiring ‘byType’
 Auto-wire a bean by property data type. In this case, since the data type of “person” bean is same as the data type of the “customer” bean’s property (Person object), so, Spring will auto wired it via setter method – “setPerson(Person person)“

4. Auto-Wiring ‘constructor’ 
Auto-wire a bean by property data type in constructor argument. In this case, since the data type of “person” bean is same as the constructor argument data type in “customer” bean’s property (Person object), so, Spring auto wired it via constructor method – “public Customer(Person person)“.

5. Auto-Wiring ‘autodetect’ 
If a default constructor is found, uses “constructor”; Otherwise, uses “byType”. In this case, since there is a default constructor in “Customer” class, so, Spring auto wired it via constructor method – “public Customer(Person person)“