java反射机制学习（二）

通过反射来set和get属性，通过反射来调用User中的method

 

 

public class User {

    public String name;
    public int password;
    public static int total = 100;
    public User(){
        super();
        total++;
    }
    public User(String name, int password){
        this.name = name;
        this.password = password;
    }
    public void setInfo(String name, int password){
        this.name = name;
        this.password = password;
    }
    public static void showTotal(){
        System.out.println("In static method showTotal,total ="+ total);
    }
    public String toString(){
        return "user name:"+name+"\t password:" +password;
    }
}

 

 

 

@SuppressWarnings("unchecked")
public class Reflection2 {
	public void resetField(Object o, String fieldName, Object newValue) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException{
		Class c = o.getClass();
		Field f = c.getField(fieldName);
		//The object o use the method get to manipulate the filed f 
		Object fv = f.get(o);
		System.out.print("Before modified:" + fieldName + "=" + fv);
		f.set(o, newValue);
		System.out.println("\t After modified:" + fieldName + "=" + f.get(o));
	}
	
	public void resetStaticField(String className,String fieldName, Object newValue) throws ClassNotFoundException, SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException{
		Class c = Class.forName(className);
		Field f = c.getDeclaredField(fieldName);
		Object fv = f.get(c);
		System.out.print("Before Modified:"+fieldName + "="+fv);
		f.set(c, newValue);
		System.out.println("\t After Modified:" + fieldName +"=" + f.get(c));
	}
	
	public void resetMethod(Object o,String methodName,Class[]argTypes,Object[] args) throws SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException{
		Class c = o.getClass();
		Method m = c.getMethod(methodName,argTypes);
		//If the method dont have the return value,the result will be null	
		Object result = m.invoke(o,args);
		System.out.println("result:"+result);
	}
	
	public void callStaticMethod(String className,String methodName, Class[] argTypes, Object[] args) throws ClassNotFoundException, SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException{
		Class c = Class.forName(className);
		Method m = c.getDeclaredMethod(methodName, argTypes);
		Object result = m.invoke(null, args);
		System.out.println("result:"+result);
	}
	
	public static void main(String args[]) throws SecurityException, IllegalArgumentException, NoSuchFieldException, IllegalAccessException, ClassNotFoundException, NoSuchMethodException, InvocationTargetException{
		User user = new User("Larry",77582);
		Reflection2 t = new Reflection2();
		//Here,the modifier of these fields are public 
		System.out.println("********************************");
		t.resetField(user,"name","Mike");
		t.resetField(user,"password",15421);
		System.out.println(user);
               
      		//Also can reset static field in this way
               // you can have a try
//		t.resetField(user, "total", 80);
		
		//Here, this method only can reset the static field
		System.out.println("********************************");
		t.resetStaticField("com.ustc.User", "total", 22);
		
		System.out.println("********************************");
		//parameter types, should be class
		Class[] argTypes = new Class[]{String.class,int.class};
		//parameter values
		Object[] args1 = new Object[]{"Alex",5555};
		t.resetMethod(user, "setInfo", argTypes, args1);
		System.out.println(user);
		t.resetMethod(user, "showTotal", null, null);

		System.out.println("********************************");
		t.callStaticMethod("com.ustc.User", "showTotal", new Class[0], new Object[0]);
	}	
}