annotationreader.java

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import java.lang.annotation.*;
import java.lang.reflect.*;

/**
 *  Read annotation information from a class at runtime using the new 
 *  JDK1.5 reflection features
 **/
public class AnnotationReader {
  AnnotatedClass ac;

  /**
   *  Constructor
   **/
  public AnnotationReader() {
    ac = new AnnotatedClass();
  }

  /**
   *  Print out runtime annotation information
   **/
  public void printAnnotations() {
    Class c = ac.getClass();
	Annotation[] annotations = c.getAnnotations();
    int numberOfAnnotations = annotations.length;
    System.out.println("Class " + c.getName() + " has " +
      numberOfAnnotations + " annotations");

    for (int i = 0 ; i < numberOfAnnotations; i++) {
      System.out.println("Annotation " + i + ": " + annotations[i] +
        ", type" + annotations[i].annotationType().getName());
    }
    
    // use reflection method to get methods defined in this class.
    Method[] ms = c.getMethods();
    
    // iterate the method list
    for(Method m: ms) {
        
        // use reflection method to get the declared annotations for this method.
        Annotation[] as = m.getDeclaredAnnotations();
        for (Annotation a:as) {
            String annotationName = a.annotationType().getName();
            System.out.println("for method:" + m.getName() + " has annotation:" + annotationName);
            if (a instanceof Accessor) {
                
                // get the attritues for this annotation.
                Accessor accAnnotation = (Accessor)a;
                System.out.println("Accessor's variable name is:" + accAnnotation.variableName());
            }
            
        }
    }
    
  }

  /**
   *  Main entry point
   *
   * @param args Command line arguments
   **/
  public static void main(String[] args) {
    AnnotationReader ar = new AnnotationReader();
    ar.printAnnotations();
  }
}