Annotation of enum members (JDK 1.5)

[Emmeran Seehuber]

Hi,

is it possible to annotate members of enums? It doesn't seem so -- at least
I can't get the values at runtime

This is my annotation class:

@Retention(RetentionPolicy.RUNTIME)
public @interface BCComment {
String value();
}

And this is the class containing the enum:

public class ByteCodeCommands {
public enum ByteCode {
@BCComment("Anfang einer Methode")
METHODPROLOG,
@BCComment("Focus auf die Instance-Variablen")
FOCUSSELFVARIABLES,
// ...
}

public static void main(String[] args) throws IOException {
// ...
for (ByteCode code : ByteCode.values()) {
Annotation[] annotations = ByteCode.class.getAnnotations();
Annotation[] annos = code.getClass().getAnnotations();
System.out.println(annotations.length);
System.out.println(annos.length);
BCComment comment = code.getClass().getAnnotation(BCComment.class);
System.out.println(comment);
}
// ...
}
}


When running this program it prints:
0
0
null

What is wrong with my code? Is it not possible to annotate enum members?

Thanks.

cu,
Emmy

 

[Tony Morris]

Hi,

is it possible to annotate members of enums? It doesn't seem so -- at least
I can't get the values at runtime

This is my annotation class:

@Retention(RetentionPolicy.RUNTIME)
public @interface BCComment {
String value();
}

And this is the class containing the enum:

public class ByteCodeCommands {
public enum ByteCode {
@BCComment("Anfang einer Methode")
METHODPROLOG,
@BCComment("Focus auf die Instance-Variablen")
FOCUSSELFVARIABLES,
// ...
}

public static void main(String[] args) throws IOException {
// ...
for (ByteCode code : ByteCode.values()) {
Annotation[] annotations = ByteCode.class.getAnnotations();
Annotation[] annos = code.getClass().getAnnotations();
System.out.println(annotations.length);
System.out.println(annos.length);
BCComment comment = code.getClass().getAnnotation(BCComment.class);
System.out.println(comment);
}
// ...
}
}


When running this program it prints:
0
0
null

What is wrong with my code? Is it not possible to annotate enum members?

Thanks.

cu,
Emmy

You are attempting to get the annotation from the class when it appears on
the fields (not the class).
This is perhaps your intention:

for (Field f : ByteCode.class.getFields()) {
Annotation[] annotations = f.getAnnotations();
System.out.println(annotations.length);
BCComment comment = f.getAnnotation(BCComment.class);
System.out.println(comment);
}

Also, take a look at java.lang.annotation.Target to restrict the constructs
that a particular annotation can appear on.

 

[Emmeran Seehuber]

Tony Morris wrote:

[...]

You are attempting to get the annotation from the class when it appears on
the fields (not the class).
This is perhaps your intention:

for (Field f : ByteCode.class.getFields()) {
Annotation[] annotations = f.getAnnotations();
System.out.println(annotations.length);
BCComment comment = f.getAnnotation(BCComment.class);
System.out.println(comment);
}

Also, take a look at java.lang.annotation.Target to restrict the
constructs that a particular annotation can appear on.

Thank you! That works.

cu,
Emmy