Dynamic injection in Spring

Question

I have 2 tax implementation classes IndianTaxCalculation and USTAxCalculation which have implementaions for calculateTax() method. I need to populate the class dynamically based on user login whether Indian or US, the respective Tax calculation method should call. How can i achieve this in Spring?

Answer 1

Try something like this:

@Autowired
@Qualifier("indian")
private TaxCalculation indianTax;
@Autowired
@Qualifier("us")
private TaxCalculation usTax;


public void calculateTaxes(Client client) {
   if (client.isFromIndia()) {
      indiaTax.calculate(client);
   } else if (client.isFromUS()) {
      usTax.calculate(client);
   }
}

Answer 2

I think the topic below can answer your question. Please refer to How to do conditional auto-wiring in Spring?

Answer 3

You can create a locator service like:

public class ServiceLocator implements ApplicationContextAware
{
  private static ApplicationContext context;
  public void setApplicationContext(ApplicationContext context)
  {
    this.context = context;
  }
  public static <T> T getServiceBean(Class<T> serviceClass, String beanName)
  {
    return context.getBean(beanName, serviceClass);
  }
}

And your service like:

public void calculateTaxes(Client client) 
{
  if (client.isFromIndia())  
  {
    ServiceLocator.getServiceBean(TaxCalculation.class, "indiaTaxBeanName").calculate(client);
  } 
  else if (client.isFromUS())  
 {
    ServiceLocator.getServiceBean(TaxCalculation.class, "usTaxBeanName").calculate(client);
 }

}