反射舉例

package cn.lee.demo;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.TypeVariable;

public class Main {
	/**
	 * 爲了看清楚Java反射部分代碼，所有異常我都最後拋出來給虛擬機處理！
	 * @param args
	 * @throws ClassNotFoundException
	 * @throws InstantiationException
	 * @throws IllegalAccessException
	 * @throws InvocationTargetException 
	 * @throws IllegalArgumentException 
	 * @throws NoSuchFieldException 
	 * @throws SecurityException 
	 * @throws NoSuchMethodException 
	 */
	public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, SecurityException, NoSuchFieldException, NoSuchMethodException {
		// TODO Auto-generated method stub
		
		//Demo1.  通過Java反射機制得到類的包名和類名
		Demo1();
		System.out.println("===============================================");
		
		//Demo2.  驗證所有的類都是Class類的實例對象
		Demo2();
		System.out.println("===============================================");
		
		//Demo3.  通過Java反射機制，用Class 創建類對象[這也就是反射存在的意義所在]，無參構造
		Demo3();
		System.out.println("===============================================");
		
		//Demo4:  通過Java反射機制得到一個類的構造函數，並實現構造帶參實例對象
		Demo4();
		System.out.println("===============================================");
		
		//Demo5:  通過Java反射機制操作成員變量, set 和 get
		Demo5();
		System.out.println("===============================================");
		
		//Demo6: 通過Java反射機制得到類的一些屬性： 繼承的接口，父類，函數信息，成員信息，類型等
		Demo6();
		System.out.println("===============================================");
		
		//Demo7: 通過Java反射機制調用類中方法
		Demo7();
		System.out.println("===============================================");
		
		//Demo8: 通過Java反射機制獲得類加載器
		Demo8();
		System.out.println("===============================================");
		
	}
	
	/**
	 * Demo1: 通過Java反射機制得到類的包名和類名
	 */
	public static void Demo1()
	{
		Person person = new Person();
		System.out.println("Demo1: 包名: " + person.getClass().getPackage().getName() + "，" 
				+ "完整類名: " + person.getClass().getName());
	}
	
	/**
	 * Demo2: 驗證所有的類都是Class類的實例對象
	 * @throws ClassNotFoundException 
	 */
	public static void Demo2() throws ClassNotFoundException
	{
		//定義兩個類型都未知的Class , 設置初值爲null, 看看如何給它們賦值成Person類
		Class<?> class1 = null;
        Class<?> class2 = null;
        
        //寫法1, 可能拋出 ClassNotFoundException [多用這個寫法]
        class1 = Class.forName("cn.lee.demo.Person");
        System.out.println("Demo2:(寫法1) 包名: " + class1.getPackage().getName() + "，" 
				+ "完整類名: " + class1.getName());
        
        //寫法2
        class2 = Person.class;
        System.out.println("Demo2:(寫法2) 包名: " + class2.getPackage().getName() + "，" 
				+ "完整類名: " + class2.getName());
	}
	
	/**
	 * Demo3: 通過Java反射機制，用Class 創建類對象[這也就是反射存在的意義所在]
	 * @throws ClassNotFoundException 
	 * @throws IllegalAccessException 
	 * @throws InstantiationException 
	 */
	public static void Demo3() throws ClassNotFoundException, InstantiationException, IllegalAccessException
	{
		Class<?> class1 = null;
		class1 = Class.forName("cn.lee.demo.Person");
		//由於這裏不能帶參數，所以你要實例化的這個類Person，一定要有無參構造函數哈～
		Person person = (Person) class1.newInstance();
		person.setAge(20);
		person.setName("LeeFeng");
		System.out.println("Demo3: " + person.getName() + " : " + person.getAge());
	}
	
	/**
	 * Demo4: 通過Java反射機制得到一個類的構造函數，並實現創建帶參實例對象
	 * @throws ClassNotFoundException 
	 * @throws InvocationTargetException 
	 * @throws IllegalAccessException 
	 * @throws InstantiationException 
	 * @throws IllegalArgumentException 
	 */
	public static void Demo4() throws ClassNotFoundException, IllegalArgumentException, InstantiationException, IllegalAccessException, InvocationTargetException
	{
		Class<?> class1 = null;
		Person person1 = null;
		Person person2 = null;
		
		class1 = Class.forName("cn.lee.demo.Person");
		//得到一系列構造函數集合
		Constructor<?>[] constructors = class1.getConstructors();
		
		person1 = (Person) constructors[0].newInstance();
		person1.setAge(30);
		person1.setName("leeFeng");
		
		person2 = (Person) constructors[1].newInstance(20,"leeFeng");
		
		System.out.println("Demo4: " + person1.getName() + " : " + person1.getAge()
				+ "  ,   " + person2.getName() + " : " + person2.getAge()
				);
		
	}
	
	/**
	 * Demo5: 通過Java反射機制操作成員變量, set 和 get
	 * 
	 * @throws IllegalAccessException 
	 * @throws IllegalArgumentException 
	 * @throws NoSuchFieldException 
	 * @throws SecurityException 
	 * @throws InstantiationException 
	 * @throws ClassNotFoundException 
	 */
	public static void Demo5() throws IllegalArgumentException, IllegalAccessException, SecurityException, NoSuchFieldException, InstantiationException, ClassNotFoundException
	{
		Class<?> class1 = null;
		class1 = Class.forName("cn.lee.demo.Person");
		Object obj = class1.newInstance();
		
		Field personNameField = class1.getDeclaredField("name");
		personNameField.setAccessible(true);
		personNameField.set(obj, "胖虎先森");
		
		
		System.out.println("Demo5: 修改屬性之後得到屬性變量的值：" + personNameField.get(obj));
		
	}
	

	/**
	 * Demo6: 通過Java反射機制得到類的一些屬性： 繼承的接口，父類，函數信息，成員信息，類型等
	 * @throws ClassNotFoundException 
	 */
	public static void Demo6() throws ClassNotFoundException
	{
		Class<?> class1 = null;
		class1 = Class.forName("cn.lee.demo.SuperMan");
		
		//取得父類名稱
		Class<?>  superClass = class1.getSuperclass();
		System.out.println("Demo6:  SuperMan類的父類名: " + superClass.getName());
		
		System.out.println("===============================================");
		
		
		Field[] fields = class1.getDeclaredFields();
		for (int i = 0; i < fields.length; i++) {
			System.out.println("類中的成員: " + fields[i]);
		}
		System.out.println("===============================================");
		
		
		//取得類方法
		Method[] methods = class1.getDeclaredMethods();
		for (int i = 0; i < methods.length; i++) {
			System.out.println("Demo6,取得SuperMan類的方法：");
			System.out.println("函數名：" + methods[i].getName());
			System.out.println("函數返回類型：" + methods[i].getReturnType());
			System.out.println("函數訪問修飾符：" + Modifier.toString(methods[i].getModifiers()));
			System.out.println("函數代碼寫法： " + methods[i]);
		}
		
		System.out.println("===============================================");
		
		//取得類實現的接口,因爲接口類也屬於Class,所以得到接口中的方法也是一樣的方法得到哈
		Class<?> interfaces[] = class1.getInterfaces();
		for (int i = 0; i < interfaces.length; i++) {
			System.out.println("實現的接口類名: " + interfaces[i].getName() );
		}
		
	}
	
	/**
	 * Demo7: 通過Java反射機制調用類方法
	 * @throws ClassNotFoundException 
	 * @throws NoSuchMethodException 
	 * @throws SecurityException 
	 * @throws InvocationTargetException 
	 * @throws IllegalAccessException 
	 * @throws IllegalArgumentException 
	 * @throws InstantiationException 
	 */
	public static void Demo7() throws ClassNotFoundException, SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException, InstantiationException
	{
		Class<?> class1 = null;
		class1 = Class.forName("cn.lee.demo.SuperMan");
		
		System.out.println("Demo7: \n調用無參方法fly()：");
		Method method = class1.getMethod("fly");
		method.invoke(class1.newInstance());
		
		System.out.println("調用有參方法walk(int m)：");
		method = class1.getMethod("walk",int.class);
		method.invoke(class1.newInstance(),100);
	}
	
	/**
	 * Demo8: 通過Java反射機制得到類加載器信息
	 * 
	 * 在java中有三種類類加載器。[這段資料網上截取]

		1）Bootstrap ClassLoader 此加載器採用c++編寫，一般開發中很少見。

		2）Extension ClassLoader 用來進行擴展類的加載，一般對應的是jre\lib\ext目錄中的類

		3）AppClassLoader 加載classpath指定的類，是最常用的加載器。同時也是java中默認的加載器。
	 * 
	 * @throws ClassNotFoundException 
	 */
	public static void Demo8() throws ClassNotFoundException
	{
		Class<?> class1 = null;
		class1 = Class.forName("cn.lee.demo.SuperMan");
		String nameString = class1.getClassLoader().getClass().getName();
		
		System.out.println("Demo8: 類加載器類名: " + nameString);
	}
	
	
	
}
/**
 * 
 * @author xiaoyaomeng
 *
 */
class  Person{
	private int age;
	private String name;
	public Person(){
		
	}
	public Person(int age, String name){
		this.age = age;
		this.name = name;
	}

	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

class SuperMan extends Person implements ActionInterface
{
	private boolean BlueBriefs;
	
	public void fly()
	{
		System.out.println("超人會飛耶～～");
	}
	
	public boolean isBlueBriefs() {
		return BlueBriefs;
	}
	public void setBlueBriefs(boolean blueBriefs) {
		BlueBriefs = blueBriefs;
	}

	@Override
	public void walk(int m) {
		// TODO Auto-generated method stub
		System.out.println("超人會走耶～～走了" + m + "米就走不動了！");
	}
}
interface ActionInterface{
	public void walk(int m);
}