调用 Spring 服务并通过构造函数发送参数

Question

I have this simple Spring Service:

@Service
public class BinCountryCheckFilterImpl {

    @Autowired
    private RiskFilterService riskFilterService;

    private Terminals terminal;    

    @Autowired
    public BinCountryCheckFilterImpl(Terminals terminal) {  
        this.terminal = terminal;
    }
}

Terminals is a object unique for each received request. Also binCountryCheckFilter should be unique for every request - it should check the data for some business condition.

I want to call the service from here:

@Service
public class FilterProcessing {

    @Autowired
    private BinCountryCheckFilterImpl binCountryCheckFilter; 

    public Response someMetohd(Terminals terminal,
              Transaction message, HttpServletRequest request) throws JAXBException, JsonProcessingException {

        switch(.......) {
            case ".......":
                // send here the args via Contructor
                binCountryCheckFilter.validateBinCountryCheckFilter(terminal);                  
                break;
            case ".........":           
                .........
                break;

                break;                                          
            }           
        }
        return null;
    }
}

But I'm not aware how to send the object terminal via the BinCountryCheckFilterImpl constructor. Is there some solution for this?

Answer 1

Constructor is meant to create objects. You say: "send here the args via Constructor" - but this means that you should create a new object of type BinCountryCheckerFilterImpl for every request, and this is not how that class is defined.

In your case BinCountryCheckFilterImpl is a bean with (default) scope singleton, meaning that only one instance of this class exists in the application context.

So instead of using parameter in constructor, just pass Terminals object (that is created per request) into the validation method:

@Service
public class BinCountryCheckFilterImpl {

  @Autowired
  private RiskFilterService riskFilterService;

  public void validateBinCountryCheckFilter(Terminals terminal) {

  }
}

If you really have to define the BinCountryCheckFilterImpl to be a prototype, you should be aware that prototypes cannot be injected into singletons by simple Autowiring.

There are many techniques for this, you can find the answers here . I don't describe them in the answer because I feel its out of scope of the question and you should really go with the solution I've provided above.