The problem is that I need to create in runtime a class like this:
public class Foo {
@Bar int value0;
@Bar int value1;
@Bar int value2;
....
}
with number of fields being decided at runtime.
I was looking at Javassist, and there you can create a new class, and add fields to it, but I haven't found a way to annotate those fields.
You can use a bytecode manipulation library like ASM:
import java.lang.reflect.Field;
import java.util.Arrays;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.Opcodes;
public class a {
public static void main(String[] args) throws Exception {
Class<?> klass = new ClassLoader(a.class.getClassLoader()) {
public Class<?> defineClass() {
ClassWriter cw = new ClassWriter(0);
cw.visit(Opcodes.V1_6, Opcodes.ACC_PUBLIC + Opcodes.ACC_SUPER,
"Foo", null, "java/lang/Object", null);
for (int i = 0; i < 3; i++) {
FieldVisitor fv = cw.visitField(0, "value" + i, "I", null, null);
fv.visitAnnotation("LBar;", true).visitEnd();
}
cw.visitEnd();
byte[] bytes = cw.toByteArray();
return defineClass("Foo", bytes, 0, bytes.length);
}
}.defineClass();
for (Field f : klass.getDeclaredFields()) {
System.out.println(f + " " + Arrays.toString(f.getAnnotations()));
}
}
}
Output:
int Foo.value0 [@Bar()]
int Foo.value1 [@Bar()]
int Foo.value2 [@Bar()]
