hmzelidrissi / spring-ioc-demo

This is a simple project to demonstrate the Spring IoC container, using XML configuration and Java annotations.

Spring IoC

This is a simple project to demonstrate the Spring IoC container, using XML configuration and Java annotations.

• @Component: This annotation is used to mark a class as a Spring bean. The IoC container will automatically detect and register the bean.

    @Component("beanName")
    public class BeanType {
        // Bean code
    }

• @Autowired: This annotation is used to inject a bean into another bean.

      @Autowired
      private BeanType bean;

  If we have:
  • Single Constructor: If your bean class has only one constructor, then starting from Spring 4.3, you can omit @Autowired. Spring will automatically use that constructor for dependency injection.
  • Multiple Constructors: If there are multiple constructors, at least one must be annotated with @Autowired to clarify which one Spring should use for injection.
• @Resource: This annotation is used to inject a bean into another bean. It is similar to @Autowired, but it is more powerful and can be used to inject beans by name.
• When we have multiple beans of the same type, we can use the @Qualifier annotation to specify which bean we want to inject.

  @Autowired
  @Qualifier("beanName")
  private BeanType bean;

• @Value: This annotation is used to inject a value into a bean.

  @Value("value")
  private String value;

• @Configuration: This annotation is used to specify a class as a configuration class.

    @Configuration
    public class AppConfig {
        @Bean
        public BeanType bean() {
            return new BeanType();
        }
    }

• @PostConstruct: This annotation is used to specify a method that should be executed after the bean has been initialized.

    @PostConstruct
    public void init() {
        // Initialization code
    }

• @PreDestroy: This annotation is used to specify a method that should be executed before the bean is destroyed.

      @PreDestroy
      public void destroy() {
          // Cleanup code
      }