spring-mvc - Spring MVC 中的通用 Controller

Question

我一直在尝试编写一个通用 Controller 来提高代码的可重用性。以下是我到目前为止所拥有的:

public abstract class CRUDController<T> {

    @Autowired
    private BaseService<T> service;

    @RequestMapping(value = "/validation.json", method = RequestMethod.POST)
    @ResponseBody
    public ValidationResponse ajaxValidation(@Valid T t,
            BindingResult result) {
        ValidationResponse res = new ValidationResponse();
        if (!result.hasErrors()) {
            res.setStatus("SUCCESS");
        } else {
            res.setStatus("FAIL");
            List<FieldError> allErrors = result.getFieldErrors();
            List<ErrorMessage> errorMesages = new ArrayList<ErrorMessage>();
            for (FieldError objectError : allErrors) {
                errorMesages.add(new ErrorMessage(objectError.getField(),
                        objectError.getDefaultMessage()));
            }
            res.setErrorMessageList(errorMesages);
        }
        return res;
    }

    @RequestMapping(method = RequestMethod.GET)
    public String initForm(Model model) {
        service.initializeForm(model);
        return "country"; // how can I make this generic too ?
    }
}

T可以是国家、项目、注册和用户等内容。我现在面临的问题是 Autowiring 过程失败并出现以下错误:

No unique bean of type [com.ucmas.cms.service.BaseService] is defined: expected single matching bean but found 4: [countryServiceImpl, itemServiceImpl, registrationServiceImpl, userServiceImpl].

是否有可能实现我所需要的？我怎样才能解决这个问题 ？

Answer 1

我建议你添加 BaseService作为 CRUDController 的构造函数参数类(class):

public abstract class CRUDController<T> {

    private final BaseService<T> service;
    private final String initFormParam;

    public CRUDController(BaseService<T> service, String initFormParam) {
        this.service = service;
        this.initFormParam;
    }

    @RequestMapping(value = "/validation.json", method = RequestMethod.POST)
    @ResponseBody
    public ValidationResponse ajaxValidation(@Valid T t, BindingResult result) {
        // same as in the example
        return res;
    }

    @RequestMapping(method = RequestMethod.GET)
    public String initForm(Model model) {
        service.initializeForm(model);
        return initFormParam;   // Now initialized by the constructor
    }
}

然后你可以为每个扩展它的子类使用 Autowiring :

public class CountryController extends CRUDController<Country> {

    @Autowired
    public CountryController(CountryService countryService) {
        super(countryService, "country");
    }
}

或者，您可以使用 @Qualifier构造函数中的注释以区分不同的 BaseService执行:

@Autowired
public CountryController(@Qualifier("countryServiceImpl") BaseService<Country> baseService) {
    super(baseService, "country");
}

更新:

截至 Spring 4.0 RC1 ，可以基于泛型类型 Autowiring 。因此，您可以使用通用 BaseService<Country>作为 Autowiring 构造函数时的参数，Spring 仍然能够确定哪个是正确的，而不会抛出任何 NoSuchBeanDefinitionException :

@Controller
public class CountryController extends CRUDController<Country> {

    @Autowired
    public CountryController(BaseService<Country> countryService) {
        super(countryService, "country");
    }
}