Java：将任何类的任何属性作为参数的方法

Question

I need to create a method that takes in argument any attribute of any class . But i dont want it to be of type String, to avoid refactoring problems while renaming an attribute and to get the errors in Markers Tab of eclipse, and not while running my application.

Having a class Person :

public class Person {

    private String name;
    // other attributes...

    // getters and setters...

}

Now the needed method :

void getAnAttributeOfAClass( <which_type_or_class_here?> attr_as_arg){

   // Now I need to get the name of attribute that would be of class Strin...

}

Is there a function or a method, by which we can specify an attribute?

For example :

Person.class.name

Would it be of class Property ?

EDIT

More exactly (@Smallhacker answer helped me), I need to verify at compile time if the argument is really an attribute of the specified class.

Person.class.name // no compile time error
Person.class.nameXXX // compile time error

Answer 1

The closest to what you want is Reflection API's Field or JavaBeans Introspector API's PropertyDescriptor .

But usually things like that are not needed in Java projects because there are libraries which handle these concerns.

You could pass a Class object along with a String name, then let your method use Introspector internally to read that property.

Answer 2

Not sure I understand you well, but there is a class java.lang.reflect.Field, that has a method getName() that would give your the name of the field.

In your example, to get field name, you would do: Person.class.getDeclaredField("name").

EDIT: to get the value of a field in an object, you would do: field.get(obj);

OK, let's say You have the following variables:

Person person = ...; // initialized with some Person
Field nameField = Person.class.getDeclaredField("name");

Now to get the name of person, you would do:

String personName = (String)nameField.get(person);

Actually, this would throw an exception because name is a private field. You can however bypass the protection by doing:

nameField.setAccessible(true);

Answer 3

Unfortunately, Java lacks an ability to reference member variables in a way that can be analyzed at compile time.

There may be some kind of library to simplify this somewhat, but it wouldn't provide a full solution due to limitations in the language itself.

Answer 4

Maybe java generics can help you with this.

You can do something like:

class YourClass<E> {
    void getAnAttributeOfAClass(E attr_as_arg){

        // some code

    }        
}

someVariable = new YourClass<Person>();

someVariable.getAnAtributeOfAClass(someObject); //this will not compile if someObject is not an instance of Person

But I still don't know what you want to do exactly inside the method.