spring Java AutoWiring

You can automatically wiring interfaces with their implementation with java annotation in Spring. This way of auto wiring giving you a better understanding of how beans are wired together.

Wiring beans in configs

appConfig

@Configuration
@ComponentScan({"com.inadram"})
public class AppConfig {
 
    @Bean(name = "customerService")
    public CustomerService getCustomerService() {
        return new CustomerServiceImplementation();
    }
 
    @Bean(name = "customerRepository")
    public CustomerRepository getCustomerRepository() {
        return new hibernateRepositoryImplementation();
    }
}

@ComponentScan Add it to top of your configuration file to mark the start point of your app for looking for the beans.

@Bean

Mark the beans as auto wired. It can be mark by name or by type.

Setup classes to use config

by Adding Autowire annotation on top of the each instance it will map to the bean which define in the config.

Private member

you can set a private member as Autowire.

customerService

public class CustomerServiceImplementation implements CustomerService {

    @Autowired
    private CustomerRepository customerRepository ;
 
    @Override
    public List<Customer> findAll() {
        return customerRepository.findAll();
    }
}

use setter injection or constructor

Also you can use setter injection or constructor as Autowire

setter injection

public class CustomerServiceImplementation implements CustomerService {
    @Autowired
    public void setCustomerRepository(CustomerRepository customerRepository) {
        System.out.println("setter injection");
        this.customerRepository = customerRepository;
    }
 
    private CustomerRepository customerRepository ;
 
    @Override
    public List<Customer> findAll() {
        return customerRepository.findAll();
    }
 
}

using it

using it is pretty much similar to past.

application

public static void main(String[] args) {
    ApplicationContext appContext = new AnnotationConfigApplicationContext(AppConfig.class);

    CustomerService service = appContext.getBean("customerService", CustomerService.class);

    System.out.println(service.findAll().get(0).getFirstName());
}

load the config and find bean that you wish to using it .

Download

feel free to download the full source code from my github.