java - NotFound 无法转换为 Throwable

Question

我想实现一个目标。我正在通过演示代码分享我的概念。

interface NotFound{
        //define one marker interface which will mark not found  
    }

class ServiceException extends RuntimeException{

}

class TeacherServiceException extends ServiceException{

}


class TeacherNotFoundException extends TeacherServiceException
implements NotFound{
    TeacherNotFoundException(){
    //if teacher is null then will throw this type of exception
   }
}


class StudentServiceException extends ServiceException{

}


class StudentNotFoundException extends StudentServiceException
implements NotFound{
    StudentNotFoundException(){
    //if student is null then will throw this type of exception
   }
}


interface HasName{
    void addName(String name);
} 


//these are the models
class Student implements HasName{

    @Override
    public void addName(String name){


    }

}


class Teacher implements HasName{
    @Override
    public void addName(String name){

    }
}

//these are the resources 


class StudentResource{

    StudentService service = new StudentService(null);

    NameSupportResource<TeacherService> support = new NameSupportResource<>();

    void addName(String name){

        support.addName(service,name);
    }

}

class TeacherResource{

    TeacherService service = new TeacherService(null);

    NameSupportResource<TeacherService> support = new NameSupportResource<>();

    void addName(String name){

        support.addName(service,name);

    }
}

class NameSupportResource<T extends HasNameService>{

    void addName(T service,String name){

        try{
            service.addName(name);
        }
        catch(NotFound e){

        }

    }
}

//these are the services

interface HasNameService<T extends HasName>{

    T addName(String name);
}

class StudentService implements HasNameService<Student>{

    Student student;

    StudentService(Student student){

        this.student = student;
    }

    @Override

    public Student addName(String name){

        if(student ==  null)
            throw new StudentNotFoundException();
        else{

            student.addName(name);

            return student; 
        }

    }

}


class TeacherService implements HasNameService<Teacher>{

    Teacher teacher;

    TeacherService(Teacher teacher){

        this.teacher = teacher;
    }

    @Override
    public Teacher addName(String name){

        if(teacher ==  null)
            throw new TeacherNotFoundException();
        else{

            teacher.addName(name);

            return teacher;
        }

    }

}

在这里您可以看到，如果 studnet 为 null 或 teacher 为 null，则它可以分别抛出 StudentNotFoundException 或 TeacherNotFoundException。

使用NameSupportResource 的目的是为了通用。因为将来我可以引入另一种模型，如 Student 或 Teacher 它们可以具有相同的名称添加操作。现在，如果任何模型为 null，我想抛出子类型异常，即 StudentNotFoundException。假设我想介绍另一个模型，即书，如果书为空，那么我将抛出 BookNotFoundException。但我想通过父类型来捕捉它。这就是我定义制造商界面的原因。正如我们所知，接口(interface)可以指向类对象。

但是我看到了一个错误

incompatible types: NotFound cannot be converted to Throwable
        catch(NotFound e){
              ^
1 error

能告诉我怎么解决吗？？

Answer 1

您只能throw 和catch 对象是Throwable 的子类型(通常是Exception 或RuntimeException).

由于这些是类，我们在 Java 中没有多重继承，这意味着您必须将异常放在一个层次结构下。

如果您的 NotFound 是一个特定的 ServiceException，您可以像那样对其进行建模(另外，您可能希望将 Exception 后缀添加到遵循惯例):

class NotFoundException extends ServiceException

然后，让您的其他“未找到”异常扩展此异常，例如:

class TeacherNotFoundException extends NotFoundException

(注意 TeacherNotFoundException 也是一个 ServiceException)

然后您将能够捕获所有“未找到”异常:

catch(NotFoundException e){
}