The constructor injection, on the other hand, uses a constructor to inject dependencies. The following code shows you how to use a constructor for injecting in DataService:

    public class BusinessServiceImpl { 
      private DataService dataService; 
      @Autowired 
      public BusinessServiceImpl(DataService dataService) { 
        super(); 
        this.dataService = dataService; 
      } 
    }

When you run the code with the preceding implementation of BusinessServiceImpl, you will see this statement in the log, asserting that autowiring took place using the constructor:

    Autowiring by type from bean name 'businessServiceImpl' via 
    constructor to bean named 'dataServiceImpl'