Reflection Java Api Best Practices

Code Source

1. create a java class nemed TestClass containing 5 methods (m_A(), m_B(), m_C(), m_D(), m_E() ) every method return a String ("A", "B" ...) :
   
   

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   package slm.abdennour.domain; import slm.abdennour.reflection.AnnoteMe; /** * * @author عبد النور التومي Abdennour TOUMI * @blog http://abdennour-insat.blogspot.com * 28 oct. 2012 */ public class TestClass { public String m_A(){ return "A"; } public String m_B(){ return "B"; } public String m_C(){ return "C"; } public String m_D(){ return "D"; } public String m_E(){ return "E"; } }

   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
2. create a parameterized annotation for methods with name: annoteMe (parameter name: "returnKey") :

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   package slm.abdennour.reflection; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; /** * @author عبد النور التومي Abdennour TOUMI * 28 oct. 2012 */ @Target(ElementType.METHOD) @Retention(RetentionPolicy.RUNTIME) public @interface AnnoteMe {       String returnKey(); }

   
   
3. annotate the methods m_B(), m_C(), m_D() with annoteMe :
   
   

   
    @AnnoteMe(returnKey="antB")
   
    public String m_B(){
   
     return "B";
   
    }
   
   
   
   
    @AnnoteMe(returnKey="antC")
   
    public String m_C(){
   
     return "C";
   
    }
   
   
   
   
    @AnnoteMe(returnKey="antD")
   
    public String m_D(){
   
     return "D";
   
    }
   

   
   
   
   
   
   
   
   
   
   
4. create a main-class that search classes via the Reflection API in the same package (TestClass should be found):
   
   

   
   
    public static Class[] getClasses(String packageName)
   
            throws ClassNotFoundException, IOException {
   
   
   
   
   
   
   
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
   
        assert classLoader != null;
   
        String path = packageName.replace('.', '/');
   
        Enumeration<URL> resources = classLoader.getResources(path);
   
        List<File> dirs = new ArrayList<File>();
   
        while (resources.hasMoreElements()) {
   
            URL resource = resources.nextElement();
   
            dirs.add(new File(resource.getFile()));
   
        }
   
        ArrayList<Class> classes = new ArrayList<Class>();
   
        for (File directory : dirs) {
   
            classes.addAll(findClasses(directory, packageName));
   
        }
   
        return classes.toArray(new Class[classes.size()]);
   
   
   
   
   
   
   
    }
   
   
   
   Invoke getClasses:
   
   
      Class[] cls=getClasses(Main.class.getPackage().getName());
   
   
   
   
   
   

5. search the methods annotated with "annoteMe" in the found classes (hier TestClass) via the Reflection API and invoke them :
   
   
   

   
   public static List<Method> getMethods(Class[] classes,Class annotat){
   
     List<Method> methodsAnnoted=new ArrayList<Method>();
   
     for(int i=0;i<classes.length;i++){
   
      Method[] subMs=classes[i].getMethods();
   
      System.out.println(subMs.length);
   
      for(int j=0;j<subMs.length;j++){
   
       //System.out.println(Calendar.getInstance().ge+"mmm : "+subMs[j].getName());
   
       Annotation[] ans=Arrays.asList(subMs).get(j).getAnnotations();
   
       for(Annotation ant:ans) {
   
         if( ant.annotationType() == annotat ) {
   
                            methodsAnnoted.add(subMs[j]);
   
                      }
   
       }
   
   
   
   
      }
   
   
   
   
     }
   
   
   
   
     return methodsAnnoted;
   
   
   
   
    }
   

   
   
   Invoke getMethods:
   List<Method> annotatedMethods=getMethods(cls, AnnoteMe.class);