Critique
A major problem with marker interfaces is that an interface defines a contract for implementing classes, and that contract is inherited by all subclasses. This means that you cannot "unimplement" a marker. In the example given, if you create a subclass that you do not want to serialize (perhaps because it depends on transient state), you must resort to explicitly throwing NotSerializableException (per ObjectOutputStream docs)
Another solution is for the language to support metadata directly:
- Both the .NET framework and Java (as of Java 5 (1.5)) provide support for such metadata. In .NET, they are called "custom attributes", in Java they are called "annotations". Despite the different name, they are conceptually the same thing. They can be defined on classes, member variables, methods, and method parameters and may be accessed using reflection.
- In Python, the term "marker interface" is common in Zope and Plone. Interfaces are declared as metadata and subclasses can use
implementsOnlyto declare they do not implement everything from their super classes.
Read more about this topic: Marker Interface Pattern
Famous quotes containing the word critique:
“In its artless cruelty, Dallas is superior to any “intelligent” critique that can be made of it. That is why intellectual snobbery meets its match here.”
—Jean Baudrillard (b. 1929)
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—Thomas Mann (1875–1955)
“... the outcome of the Clarence Thomas hearings and his subsequent appointment to the Supreme Court shows how misguided, narrow notions of racial solidarity that suppress dissent and critique can lead black folks to support individuals who will not protect their rights.”
—bell hooks (b. c. 1955)