Spring boot: @Autowired annotation example

Auto wiring is a technique, where spring automatically inject a bean by using type, name (or) constructor arguments. Spring supports 4 modes of auto wiring.

         1. No Auto wiring

         2. Auto wiring by name

         3. Auto wiring by type

         4. Auto wiring by constructor.

I explained above modes in my previous tutorials.

Autowiring modes

Autowiring by name

Autowiring by type

Autowiring by 'constructor'

Resolve autowiring conflict using primary attribute

Tune autowiring with qualifiers

In this post, I am going to show, how can you use @Autowired annotation to inject beans.

Define a bean in any configuration class.

         @Bean(autowire = Autowire.BY_NAME, name = "defaultEmployee")

         public Employee getDefaultEmployee() {

                  Employee emp = new Employee();

                  emp.setFirstName("NO_NAME");

                  emp.setId(-1);

                  emp.setLastName("NO_NAME");

                  return emp;

         }

As you see, I given a name 'defaultEmployee' to the bean.

Use @Autowired and @Qualifier annotations to inject the bean.

        

@Autowired

@Qualifier("defaultEmployee")

private Employee defaultEmployee;

Find the below working application.

Employee.java

package com.sample.myApp.model;

import org.springframework.stereotype.Component;

@Component
public class Employee {

 private int id;
 private String firstName;
 private String lastName;

 public int getId() {
  return id;
 }

 public void setId(int id) {
  this.id = id;
 }

 public String getFirstName() {
  return firstName;
 }

 public void setFirstName(String firstName) {
  this.firstName = firstName;
 }

 public String getLastName() {
  return lastName;
 }

 public void setLastName(String lastName) {
  this.lastName = lastName;
 }

 @Override
 public String toString() {
  return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + "]";
 }

}

EmployeeConfiguration.java

package com.sample.myApp.Configuration;

import org.springframework.beans.factory.annotation.Autowire;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.sample.myApp.model.Employee;

@Configuration
public class EmployeeConfiguration {

 @Bean(autowire = Autowire.BY_NAME, name = "defaultEmployee")
 public Employee getDefaultEmployee() {
  Employee emp = new Employee();
  emp.setFirstName("NO_NAME");
  emp.setId(-1);
  emp.setLastName("NO_NAME");
  return emp;
 }

 @Bean(autowire = Autowire.BY_NAME, name = "genericEmployee")
 public Employee getGenericEmployee() {
  Employee emp = new Employee();
  emp.setFirstName("krishna");
  emp.setId(1);
  emp.setLastName("Gurram");
  return emp;
 }
}

EmployeeUtil.java

package com.sample.myApp.util;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;

import com.sample.myApp.model.Employee;

@Component
public class EmployeeUtil {

 @Autowired
 @Qualifier("defaultEmployee")
 private Employee defaultEmployee;

 @Autowired
 @Qualifier("genericEmployee")
 private Employee genericEmployee;

 public Employee getDefaultEmployee() {
  return defaultEmployee;
 }

 public Employee getGenericEmployee() {
  return genericEmployee;
 }

}

Application.java

package com.sample.myApp;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

import com.sample.myApp.util.EmployeeUtil;

@SpringBootApplication
public class Application {

 public static void main(String args[]) {
  ConfigurableApplicationContext applicationContext = SpringApplication.run(Application.class, args);

  EmployeeUtil empUtil = applicationContext.getBean(EmployeeUtil.class);

  System.out.println(empUtil.getDefaultEmployee());
  System.out.println(empUtil.getGenericEmployee());

  applicationContext.close();
 }
}

Output

Employee [id=-1, firstName=NO_NAME, lastName=NO_NAME]

Employee [id=1, firstName=krishna, lastName=Gurram]

Previous                                                 Next                                                 Home