package com.semanticsquare.jvm;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class ReflectionDemo {
	// Class object access demonstration + meta-information access
	public static void demoClassObjectAccess() {
	    System.out.println("\nIn demoClassObjectAccess ...");
	    
	    // Using objectRef.getClass()
	 	String[] strArray = {"a", "b", "c"};
	 	System.out.println("\nstrArray.getClass().getName(): " + strArray.getClass().getName());
	    
	    // Using for Class.forName
	    Class clazz = null;
	    try {
		    clazz = Class.forName("com.semanticsquare.jvm.User");		    
		} catch(ClassNotFoundException e) {
            System.out.println("\nCan't find class ...");		
		}		
		System.out.println("\nclazz.getName(): " + clazz.getName());
		System.out.println("clazz.isInterface(): " + clazz.isInterface());
		System.out.println("clazz.getInterfaces(): " + clazz.getInterfaces().length);
		System.out.println("clazz.getSuperclass().getName(): " + clazz.getSuperclass().getName());
				
		// Exception is thrown as Class.forName cannot be used on primitives
		try {
		    System.out.println("\nClass.forName(\"boolean\").getName(): " + Class.forName("boolean").getName());
		} catch(ClassNotFoundException e) {
            System.out.println("\nClassNotFoundException due to Class.forName(\"boolean\").getName()");		
		}			
		
		// Using .class
		System.out.println("\nint.class.getName(): " + int.class.getName());
	}
	
	// Demonstrates instance creation & method invocation
	public static void demoCoreReflection(Class clazz) throws InstantiationException, 
	        IllegalAccessException, NoSuchMethodException, InvocationTargetException{
	    System.out.println("\nIn demoCoreReflection ...");
	    
	    Object object = null;
		try {
		    object = clazz.newInstance(); // MUST HAVE DEFAULT CONSTRUCTOR		    
		} catch(InstantiationException e) {	
            System.out.println("Can't instantiate ...");		
		} catch (IllegalAccessException e) {	
            System.out.println("Can't access ...");		
		}		
		System.out.println("object.getClass(): " + object.getClass().getName());
	    
		for (Method m : clazz.getDeclaredMethods()) {
		    System.out.println("Method name: " + m.getName());
		    if (m.getReturnType() == void.class) {
		    	System.out.println("Method's return type is void!!! ");
		    }
		}
		for (Constructor c : clazz.getDeclaredConstructors()) {
		    System.out.println("Constructor: " + c.getName() + ", # parameters: " + c.getParameterTypes().length);
		}
		
		// Fetch constructor & invoke it
		@SuppressWarnings("unchecked")
		Constructor<User> userConstructor = clazz.getDeclaredConstructor(int.class, String.class, String.class, String.class, String.class);
		@SuppressWarnings("unchecked")
		User user = userConstructor.newInstance(101, "john", "john@semanticsquare.com", "male", "user");
		
		// Fetch method & invoke it
	    @SuppressWarnings("unchecked")
		Method m = clazz.getDeclaredMethod("saveWebLink", String.class, String.class);
		Object result = m.invoke(user, "http://www.google.com", "Google");
		System.out.println("Result of invoking saveWebLink: " + ((Boolean)result).booleanValue());
	}
	
	public static void main(String[] args) throws Exception {
    	demoClassObjectAccess();		
		demoCoreReflection(Class.forName("com.semanticsquare.jvm.User"));
	}
}