在抽象 class 的具体 classes 中自动装配而不是实现接口

Question

我正在使用 Spring 启动并且我有以下任务模型

public class Task {
    private String name;
    private TaskType type; // ManualTask, AutomatedTask
    private boolean completed;
    //....other fields

    //getters and setters
}

一个控制器

@Controller
@RequestMapping("/api/task")
public class TaskController {

    @Autowired
    private TaskService taskService;

    @GetMapping("/{taskId}/handle")
    public String handle(Model model, @PathVariable("taskId") Long taskId) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
        try {
            Task task = taskService.handle(taskId);
            model.addAttribute("task", task);
        } catch (Exception e) {
            return "errorpage";
        }
        return "successpage";
    }
}

我有接口

public interface TaskService {

    Task findById(Long taskId);

    Task handleTask(Long taskId) throws ClassNotFoundException, InstantiationException, IllegalAccessException;

}

抽象class实现了接口：

@Service
public abstract class TaskServiceImpl implements TaskService {

    @Autowired
    private TaskRepository taskRepository;

    private static final String PATH_OF_CLASS = "com.task.service.impl";

    protected abstract Task doTypeSpecificTask(Long taskId);

    @Override
    public Task findById(Long taskId) {
        return taskRepository.findById(taskId).get();
    }

    @Override
    public Task handleTask(Long taskId) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
        Task task = findById(taskId);
        TaskServiceImpl service = getHandlerService(task);
        return service.doTypeSpecificTask(taskId);
    }

    private TaskServiceImpl getHandlerService(Task task) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
        String serviceClassName = PATH_OF_CLASS.concat(".").concat(task.getTaskType().getName()).concat("Service");
        Class<?> serviceClass = Class.forName(serviceClassName);
        if (!TaskServiceImpl.class.isAssignableFrom(serviceClass)) {
            throw new RuntimeException("Service class " + serviceClassName + " did not implements " + TaskServiceImpl.class.getName());
        }
        Object serviceObject = serviceClass.newInstance();
        TaskServiceImpl service = (TaskServiceImpl) serviceObject;
        return service;
    }


}

以及扩展抽象的具体服务class

@Service
@Primary
public class ManualTaskService extends TaskServiceImpl {

    @Autowired
    private TaskRepository taskRepository;

    @Autowired
    private ManualTaskHandlerService manualTaskHandlerService;

    @Override
    protected Task doTypeSpecificTask(Long taskId) {
        Task task = findById(taskId);
        manualTaskHandlerService.handleManualTask(task);
        task.setCompleted(true);
        return taskRepository.save(task);
    }
}

@Service
public class AutomatedTaskService extends TaskServiceImpl {

    @Autowired
    private TaskRepository taskRepository;

    @Autowired
    private AutomatedTaskHandlerService automatedTaskHandlerService;

    @Override
    protected Task doTypeSpecificTask(Long taskId) {
        Task task = findById(taskId);
        automatedTaskHandlerService.handleAutomatedTask(task);
        task.setCompleted(true);
        return taskRepository.save(task);
    }
}

public interface TaskRepository extends JpaRepository<Task, Long> {

}

ManualTaskService 或 AutomatedTaskService 是根据运行时的任务类型动态选择的。

现在，没有 @Primary，我得到以下错误：

Field taskService in com.test.controller.TaskController required a single bean, but 2 were found:
- manualTaskService
- automatedTaskService

Action:

Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed

在 ManualTaskService 中设置了 @Primary，ManualTaskService 中的 doTypeSpecificTask 可以工作，但在 AutomatedTaskService 中它会失败，因为 automatedTaskHandlerService.handleAutomatedTask(task)。从 AutomatedTaskService 调用 taskRepository 也会失败。

我试过使用 @Qualifier 以及将摘要 class 中的所有 @Autowired 定义为受保护，但没有任何效果。我做错了什么？

Answer 1

每个限定符应该有不同的名称：

@Autowired
@Qualifier("manualTaskService")
private TaskServiceImpl manualTaskService;

@Autowired
@Qualifier("automatedTaskService")
private TaskServiceImpl automatedTaskService;

在服务中定义：

@Service("manualTaskService")
public class ManualTaskService extends TaskServiceImpl {

@Service("automatedTaskService")
public class AutomatedTaskService extends TaskServiceImpl {

Answer 2

我使用thislink中提到的工厂模式解决了这个问题（感谢@user7294900提供link）

我完全删除了摘要class TaskServiceImpl。相反，我创建了两个新接口 ManualTaskService 和 AutomatedTaskService 都扩展了 TaskService 接口

public interface ManualTaskService extends TaskService {
}

public interface AutomatedTaskService extends TaskService {     
}

然后我创建了一个TaskServiceFactory

@Component
public class TaskServiceFactory {

    @Autowired
    private ManualTaskService manualTaskService;

    @Autowired
    private AutomatedTaskService automatedTaskService;

    public TaskService getService(TaskType type) throws Exception {
        switch (type) {
        case MANUAL_TASK:
            return manualTaskService;
        case AUTOMATED_TASK:
            return automatedTaskService;
        default:
            throw new Exception("Unrecognized task type");
        }
    }
}

接下来我为 ManualTaskService 和 AutomatedTaskService

创建了实现

@Service
public class ManualTaskServiceImpl implements ManualTaskService {

    @Autowired
    private TaskRepository taskRepository;

    @Autowired
    private ManualTaskHandlerService manualTaskHandlerService;

    @Override
    public Task findById(Long taskId) {
        return taskRepository.findById(taskId).get();
    }

    @Override
    public Task handleTask(Long taskId) throws Exception {
        Task task = findById(taskId);
        manualTaskHandlerService.handleManualTask(task);
        task.setCompleted(true);
        return taskRepository.save(task);
    }
}


@Service
public class AutomatedTaskServiceImpl implements AutomatedTaskService {

    @Autowired
    private TaskRepository taskRepository;

    @Autowired
    private AutomatedTaskHandlerService automatedTaskHandlerService;

    @Override
    public Task findById(Long taskId) {
        return taskRepository.findById(taskId).get();
    }

    @Override
    public Task handleTask(Long taskId) throws Exception {
        Task task = findById(taskId);
        automatedTaskHandlerService.handleAutomatedTask(task);
        task.setCompleted(true);
        return taskRepository.save(task);
    }

}

最后我更新了控制器以从用户那里获取任务类型，然后使用 TaskServiceFactory 根据类型获取正确的服务实例

@Controller
@RequestMapping("/api/task")
public class TaskController {

    @Autowired
    private TaskServiceFactory taskServiceFactory;

    @PostMapping("/{taskId}/handle")
    public String handle(Model model, @PathVariable("taskId") Long taskId, HttpServletRequest request) throws Exception {
        try {
            TaskType type = TaskType.valueOf(request.getParameter("type"));
            Task task = taskServiceFactory.getService(type).handleTask(taskId, request);
            model.addAttribute("task", task);
        } catch (Exception e) {
            return "errorpage";
        }
        return "successpage";
    }
}

在抽象 class 的具体 classes 中自动装配而不是实现接口

Autowiring in concrete classes of an abstract class than implements an interface

java

abstract-class

interface

autowired

spring-boot