Spring MVC 中的抽象类依赖注入

Question

我有一个用于登录功能的抽象类

@Component
public abstract class SignIn {    

    public abstract LogInOperationToken signin(User user, HttpServletRequest request);


}

它由两个具体的类FacebookSignInImpl 和NormalSignInImpl 实现，它们也都被注释为@Component。

现在，我有一个服务类如下：

 @Service
public class SignInService {

    @Autowired(required = true)
     private SignIn signIn;    


    public SignInService(@Qualifier("signIn") SignIn signin) {
    this.signIn = signin;
    }


    public LogInOperationToken signin(User user, HttpServletRequest request) {
        return signIn.signin(user,request);
    }
}

如您所见，它将抽象类作为构造函数参数。

我试图从控制器类中检查一些标志，并在此基础上为抽象类分配正确的实现：普通或 facebook 登录。如果没有 Spring 依赖注入，我会执行以下操作：

SignIn signIn = null; 

if(flag.equals("facebook")){
    signIn  = new FacebookSignInImpl();
}
else{
    signIn = new NormalSignInImpl();
}

SignInService signInService = new SignInService(signIn);
signInService.signIn(user, request);

既然SignIn 是抽象类，我怎么能@Autowire 将它分配给SignInService 中的构造函数。如果您需要更多说明，请发表评论。谢谢。

Answer 1

您不能创建抽象类的@Component，并且您的应用程序设计不完美。请遵循以下模式

public abstract class SignIn {
    public abstract LogInOperationToken signin(User user, HttpServletRequest request);
}

@Component("fcaebookSignIn")
public class FcaebookSignIn {
    public LogInOperationToken signin(User user, HttpServletRequest request) {
        // implementation code
    }
}

@Component("normalSignIn")
public class NormalSignIn {
    public LogInOperationToken signin(User user, HttpServletRequest request) {
        // implementation code
    }
}

然后我强烈建议您为不同类型的登录创建不同的控制器或休息端点

@Controller
public class SignInController {

    @Autowired
    @Qualifier(value="fcaebookSignIn")
    private SignIn fcaebookSignIn;

    @Autowired
    @Qualifier(value="normalSignIn")
    private SignIn normalSignIn;

    @RequestMapping (method = RequestMethod.POST, path = '/normal/signIn') 
    public User normalSignIn(@RequestBody User user, HttpServletRequest request) {
        normalSignIn.signIn(user, request);
    }

    @RequestMapping (method = RequestMethod.POST, path = '/facebook/signIn') 
    public User facebookSignIn(@RequestBody User user, HttpServletRequest request) {
        fcaebookSignIn.signIn(user, request);
    }
}

但如果您必须使用单个端点，那么以下应该可以工作

@Controller
public class SignInController {

    @Autowired
    private ApplicationContext context;

    private SignIn signIn;

    @RequestMapping (method = RequestMethod.POST, path = '/signIn') 
    public User normalSignIn(@RequestBody User user, HttpServletRequest request) {
        String flag = request.getParameter("flag"); // populate this from wherever you are getting this flag

        if(flag.equals("facebook")) {
            signIn  = context.getBean(FcaebookSignIn.class)
        }
        else{
            signIn  = context.getBean(NormalSignIn.class)
        }

        signIn.signIn(user, request);
    }
}