Top Most Java 5 Custom annotation Example

Step 1) create a interface as below

A)


package com.myapp.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Target;

/*
 * Annotations can be greatly used by the Build-time
 * Tools and Run-time Environments to do a bunch of
 * useful tasks like Code Generation, Validation.Java 6 has introduced a
 * new JSR called JSR 269, which is the Pluggable Annotation Processing API.
 * With this API, now it is possible for the Application Developers to write a
 * Customized Annotation Processor which can be plugged-in to
 * the code to operate on the set of Annotations that appear in a Source File.
 * */
@Target(value = { ElementType.TYPE })
public @interface ClassLevelAnnotationInterface {

}

B)


package com.myapp.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Target;

@Target(value = { ElementType.METHOD })
public @interface MethodLevelAnnotationInterface {

}

Stpe 2) Now apply your above annotation on class and method as follows


package com.myapp.annotation;

/*
 * Annotations can be greatly used by the Build-time
 * Tools and Run-time Environments to do a bunch of
 * useful tasks like Code Generation, Validation.
 * Java 6 has introduced a  new JSR called JSR 269,
 * which is the Pluggable Annotation Processing API.
 * With this API, now it is possible for the Application Developers to write a
 * Customized Annotation Processor which can be plugged-in to
 * the code to operate on the set of Annotations that appear in a Source File.
 * */
@ClassLevelAnnotationInterface()
public class AnnotationApplliedOnClassAndMethod {
@MethodLevelAnnotationInterface()
public void myAnnotatedMethod() {
}
}

Step 3) Now create a class like below that extends AbstractProcessor and implement process method


package com.myapp.annotation;

import java.util.Iterator;
import java.util.Set;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.TypeElement;

@SupportedAnnotationTypes(value = ("*"))
@SupportedSourceVersion(SourceVersion.RELEASE_0)
public class TestAnnotationProcessor extends AbstractProcessor {

@Override
public boolean process(Set<? extends TypeElement> annotations,
RoundEnvironment roundEnv) {
for (Iterator iterator = annotations.iterator(); iterator.hasNext();) {
TypeElement typeElement = (TypeElement) iterator.next();
System.out.println(typeElement.getQualifiedName());
}
System.out.println(roundEnv.getRootElements().toString());
return true;
}

}


Step 4) Now Test your above written classes as follows


package com.myapp.annotation;

import java.util.Iterator;
import java.util.Set;

public class TestMyAnnonatedClasses {

public static void main(String[] args) {
TestAnnotationProcessor procesor = new TestAnnotationProcessor();
Set<String> supportedAnnotationTypes = procesor
.getSupportedAnnotationTypes();
for (Iterator<String> iterator = supportedAnnotationTypes.iterator(); iterator
.hasNext();) {
String annotationType = iterator.next();
System.out.println(annotationType);

}
Set<String> supportedOptions = procesor.getSupportedOptions();
for (Iterator iterator = supportedOptions.iterator(); iterator
.hasNext();) {
String supportedOption = (String) iterator.next();
System.out.println(supportedOption);

}
System.out.println(procesor.getSupportedSourceVersion().name());
}
}