3 ways to initialize and destroy Spring beans

There are 3 ways to initialize (and destroy) spring beans
1. Using init-method and destroy-method attributes
2. Implementing InitializingBean and DisposableBean interfaces
3. Using @PostConstruct and @PreDestroy Annotations (available only in Spring >=2.5)


1. Using init-method and destroy-method attributes
Certain bean methods can designated as initializing and destroying methods using the init-method and destroy-method attributes. Like so:

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<bean
    id="studentService"

    class="initMethod.StudentServiceImpl"

    init-method="subscribe"

    destroy-method="unsubscribe"/>

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2. Implementing InitializingBean and DisposableBean interfaces
The bean can implement these methods InitializingBean.afterPropertiesSet() and DisposableBean.destroy(). Like so:

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public class StudentServiceImpl implements StudentService, InitializingBean, DisposableBean {

    @Override

    public boolean isExists(long studentId) {

        // A fake implementation

        if ( studentId % 2 == 0 )

        {

            return true;

        }

        else

        {

            return false;

        }

    }

    @Override

    public void afterPropertiesSet() throws Exception 

    {

        // subscribe logic goes here

    }

    @Override

    public void destroy() throws Exception 

    {

       // unsubscribe logic goes here

    }

}

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3. Using @PostConstruct and @PreDestroy Annotations
Note that both of these are JSR-250 annotations (here is a nice introduction to JSR-250 support introduced in spring 2.5).

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@PostConstruct
public void subscribe()
{
  // subscribe logic goes here
}


@PreDestroy
public void unsubscribe()
{
  // unsubscribe logic goes here
}

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