反射机制

以下代码可以初步的了解反射

package com.lbx.test;

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

import com.lbx.model.Person;

public class TestReflection {

	/**
	 * 测试获取Class对象
	 */
	public static void testgetClassObject(){
		//通过getClass来获得
		Person p = new Person("李斌选");
		Class c = p.getClass();
		System.out.println(c.getName());
		
		//使用类名.class来获得
		Class c2 = Person.class;
		System.out.println(c2.getPackage());
		
		//使用Class.forName来获得
		try {
			Class c3 = Class.forName("com.lbx.model.Person");
			System.out.println(c3.getSimpleName());
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	

	/**
	 * 测试属性操作
	 */
	public static void testField(){
		try {
			Class c = Class.forName("com.lbx.model.Person");
			Field[] fs = c.getFields();
			for (int i = 0; i < fs.length; i++) {
				Field field = fs[i];
				System.out.println("属性类型："+field.getType().getName());   //属性是公有才行。 
				
				//得到某个对象指定属性的值
				Field f = c.getField("name");
				System.out.println(f.get(new Person("李斌选")));
				
				//得到类的静态属性
				Field f2= c.getField("age");
				System.out.println("类的静态属性值："+f2.get(c));
			}
 			
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	

	/**
	 * 测试执行对象或类的方法
	 */
	private static void testMethod(){
		try {
			Class c = Class.forName("com.lbx.model.Person");
			Method[] ms = c.getMethods();
			for (int i = 0; i < ms.length; i++) {
				Method method = ms[i];
				System.out.println(method.getName()); 
			}
			
			//对象方法的调用
			Person p = new Person("李斌选");
			Method m = c.getMethod("test1",null);
			m.invoke(p, null);
			//有参数传入的方法的调用!
			Method m2 = c.getMethod("test2",int.class,String.class);
			m2.invoke(p,22,"aaa");
			
			//类的静态方法调用
			Method m3 = c.getMethod("test3", null);
			m3.invoke(null);
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 测试构造新的对象
	 */
	private static void testConstructor(){
		try {
			Class c = Class.forName("com.lbx.model.Person");
			Constructor con = c.getConstructor();
			Person p = (Person) con.newInstance();
			p.setName("ddd");
			System.out.println(p.getName());
			
			Constructor con2 = c.getConstructor(String.class);
			Person p2 = (Person) con2.newInstance("eee");
			System.out.println(p2.getName());
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 测试某个对象是否为某个类的对象
	 */
	private static void testIsInstance(){
		Person p = new Person();
		Class c = TestReflection.class;
		Class c2 = Person.class;
		System.out.println(c.isInstance(p));
		System.out.println(c2.isInstance(p));
	}
	
	public static void main(String[] args) {
		testgetClassObject();
		testField();
		testMethod();
		testConstructor();
		testIsInstance();
	}
	
}