Injecting a bean inside another bean and use it in the constructor?

Question

I have a bean that looks like this:

@Component
@Scope("session")
public class AlarmChartSettingsBean implements Serializable {
...

Inside this bean i inject another bean like this:

@Inject
private SessionInfoBean sessionInfoBean;

Then i call the injected bean inside the constructor of the first bean like this:

public AlarmChartSettingsBean() {

    String atcaIp = sessionInfoBean.getNwConfigBean().getAtcaIP();
}

The problem is that the injected bean is null. So the question is when is that bean injected? Can i use it inside the constructor or i should use it after the bean has been constructed?

Answer 1

The constructor of a Spring bean is called before Spring has any chance to autowire any fields. This explains why sessionInfoBean is null inside the constructor.

If you want to initialize a Spring bean, you can:

• annotate a method with @PostConstruct:

  @PostConstruct
  public void init() {
      String atcaIp = sessionInfoBean.getNwConfigBean().getAtcaIP();
  }
  

• implement InitializingBean and write the initialization code inside the afterPropertiesSet method:

  public class AlarmChartSettingsBean implements Serializable, InitializingBean {
  
      @Override
      void afterPropertiesSet() {
          String atcaIp = sessionInfoBean.getNwConfigBean().getAtcaIP();
      }
  
  }