#JAVA ANNOTATIONS FULL#
You include any and all error messages in full - best also formatted as code block Using annotationsĪnnotations are straightforward to use they merely require that an appropriate annotation type be placed directly before the Java language element being annotated.Your code is properly formatted as code block - see the sidebar (About on mobile) for instructions We can define our own annotation that can be used to mark a class as being a particular concept or entity etc. Such marker interface can now be replaced with annotations. This interface is a marker interface in that it does not require any methods to be implemented but indicates that a class is capable of being serialized via the Java Serialization mechanism. This is not a particularly radical idea and indeed there is an example of such an interface in the Java language itself - the java.io.Serializable interface. These are interfaces that may not contain any methods, but are used to denote a particular concept or entity within an application. None of these requirements are new and indeed many developers have found ways of overcoming the lack of any annotation-like feature in previous versions of Java.įor example, I have tended to make extensive use of Marker Interfaces over the last few years.
One example of an annotation is to note that a method has been deprecated, or that it overrides a method in the superclass. For example, they may annotate a method, class or instance variable.
In the case of Java this means that they provide information about various elements of a Java class. Java AnnotationsĪnnotations are presented as metadata – that is data about data. We will follow this by considering some of the drawbacks of Java annotations. In this column we will look at what a Java annotation is, what they are used for, how you actually use them in your Java code an dhow you can define your own. Now that a little water has flowed under the bridge, I think it is time to revisit Java Annotations.
At the time I noted their presence, but did not feel particularly excited about their appearance. The J2SE 5.0 release of Java introduced many new language features, one of which is called annotations.