How to inject ApplicationContext itself

Easy, using the ApplicationContextAware interface.

public class A implements ApplicationContextAware {
  private ApplicationContext context;

  public void setApplicationContext(ApplicationContext context) {
      this.context = context;
  }
}

Then in your actual applicationContext you only need to reference your bean.

<bean id="a" class="com.company.A" />

Previous comments are ok, but I usually prefer:

@Autowired private ApplicationContext applicationContext;