The setter injection

The setter injection is used to inject the dependencies through setter methods. In the following example, the instance of DataService uses the setter injection:

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

Actually, in order to use the setter injection, you do not even need to declare a setter method. If you specify @Autowired on the variable, Spring automatically uses the setter injection. So, the following code is all that you need for the setter injection for DataService:

    public class BusinessServiceImpl { 
      @Autowired 
      private DataService dataService; 
    }