laixintao/JavaReflection.java

## JavaReflection.java
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 {
    /**
     * 为了看清楚Java反射部分代码，所有异常我都最后抛出来给虚拟机处理！
     * @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.  通过Java反射机制得到类的包名和类名
        Demo1();
        System.out.println("===============================================");

        //Demo2.  验证所有的类都是Class类的实例对象
        Demo2();
        System.out.println("===============================================");

        //Demo3.  通过Java反射机制，用Class 创建类对象[这也就是反射存在的意义所在]，无参构造
        Demo3();
        System.out.println("===============================================");

        //Demo4:  通过Java反射机制得到一个类的构造函数，并实现构造带参实例对象
        Demo4();
        System.out.println("===============================================");

        //Demo5:  通过Java反射机制操作成员变量, set 和 get
        Demo5();
        System.out.println("===============================================");

        //Demo6: 通过Java反射机制得到类的一些属性： 继承的接口，父类，函数信息，成员信息，类型等
        Demo6();
        System.out.println("===============================================");

        //Demo7: 通过Java反射机制调用类中方法
        Demo7();
        System.out.println("===============================================");

        //Demo8: 通过Java反射机制获得类加载器
        Demo8();
        System.out.println("===============================================");

    }

    /**
     * Demo1: 通过Java反射机制得到类的包名和类名
     */
    public static void Demo1()
    {
        Person person = new Person();
        System.out.println("Demo1: 包名: " + person.getClass().getPackage().getName() + "，"
                + "完整类名: " + person.getClass().getName());
    }

    /**
     * Demo2: 验证所有的类都是Class类的实例对象
     * @throws ClassNotFoundException
     */
    public static void Demo2() throws ClassNotFoundException
    {
        //定义两个类型都未知的Class , 设置初值为null, 看看如何给它们赋值成Person类
        Class<?> class1 = null;
        Class<?> class2 = null;

        //写法1, 可能抛出 ClassNotFoundException [多用这个写法]
        class1 = Class.forName("cn.lee.demo.Person");
        System.out.println("Demo2:(写法1) 包名: " + class1.getPackage().getName() + "，"
                + "完整类名: " + class1.getName());

        //写法2
        class2 = Person.class;
        System.out.println("Demo2:(写法2) 包名: " + class2.getPackage().getName() + "，"
                + "完整类名: " + class2.getName());
    }

    /**
     * Demo3: 通过Java反射机制，用Class 创建类对象[这也就是反射存在的意义所在]
     * @throws ClassNotFoundException
     * @throws IllegalAccessException
     * @throws InstantiationException
     */
    public static void Demo3() throws ClassNotFoundException, InstantiationException, IllegalAccessException
    {
        Class<?> class1 = null;
        class1 = Class.forName("cn.lee.demo.Person");
        //由于这里不能带参数，所以你要实例化的这个类Person，一定要有无参构造函数哈～
        Person person = (Person) class1.newInstance();
        person.setAge(20);
        person.setName("LeeFeng");
        System.out.println("Demo3: " + person.getName() + " : " + person.getAge());
    }

    /**
     * Demo4: 通过Java反射机制得到一个类的构造函数，并实现创建带参实例对象
     * @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");
        //得到一系列构造函数集合
        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: 通过Java反射机制操作成员变量, 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: 修改属性之后得到属性变量的值：" + personNameField.get(obj));

    }


    /**
     * Demo6: 通过Java反射机制得到类的一些属性： 继承的接口，父类，函数信息，成员信息，类型等
     * @throws ClassNotFoundException
     */
    public static void Demo6() throws ClassNotFoundException
    {
        Class<?> class1 = null;
        class1 = Class.forName("cn.lee.demo.SuperMan");

        //取得父类名称
        Class<?>  superClass = class1.getSuperclass();
        System.out.println("Demo6:  SuperMan类的父类名: " + superClass.getName());

        System.out.println("===============================================");


        Field[] fields = class1.getDeclaredFields();
        for (int i = 0; i < fields.length; i++) {
            System.out.println("类中的成员: " + fields[i]);
        }
        System.out.println("===============================================");


        //取得类方法
        Method[] methods = class1.getDeclaredMethods();
        for (int i = 0; i < methods.length; i++) {
            System.out.println("Demo6,取得SuperMan类的方法：");
            System.out.println("函数名：" + methods[i].getName());
            System.out.println("函数返回类型：" + methods[i].getReturnType());
            System.out.println("函数访问修饰符：" + Modifier.toString(methods[i].getModifiers()));
            System.out.println("函数代码写法： " + methods[i]);
        }

        System.out.println("===============================================");

        //取得类实现的接口,因为接口类也属于Class,所以得到接口中的方法也是一样的方法得到哈
        Class<?> interfaces[] = class1.getInterfaces();
        for (int i = 0; i < interfaces.length; i++) {
            System.out.println("实现的接口类名: " + interfaces[i].getName() );
        }

    }

    /**
     * Demo7: 通过Java反射机制调用类方法
     * @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调用无参方法fly()：");
        Method method = class1.getMethod("fly");
        method.invoke(class1.newInstance());

        System.out.println("调用有参方法walk(int m)：");
        method = class1.getMethod("walk",int.class);
        method.invoke(class1.newInstance(),100);
    }

    /**
     * Demo8: 通过Java反射机制得到类加载器信息
     *
     * 在java中有三种类类加载器。[这段资料网上截取]

        1）Bootstrap ClassLoader 此加载器采用c++编写，一般开发中很少见。

        2）Extension ClassLoader 用来进行扩展类的加载，一般对应的是jre\lib\ext目录中的类

        3）AppClassLoader 加载classpath指定的类，是最常用的加载器。同时也是java中默认的加载器。
     *
     * @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: 类加载器类名: " + 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("超人会飞耶～～");
    }

    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("超人会走耶～～走了" + m + "米就走不动了！");
    }
}
interface ActionInterface{
    public void walk(int m);
}
	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 {
	/**
	* 为了看清楚Java反射部分代码，所有异常我都最后抛出来给虚拟机处理！
	* @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. 通过Java反射机制得到类的包名和类名
	Demo1();
	System.out.println("===============================================");

	//Demo2. 验证所有的类都是Class类的实例对象
	Demo2();
	System.out.println("===============================================");

	//Demo3. 通过Java反射机制，用Class 创建类对象[这也就是反射存在的意义所在]，无参构造
	Demo3();
	System.out.println("===============================================");

	//Demo4: 通过Java反射机制得到一个类的构造函数，并实现构造带参实例对象
	Demo4();
	System.out.println("===============================================");

	//Demo5: 通过Java反射机制操作成员变量, set 和 get
	Demo5();
	System.out.println("===============================================");

	//Demo6: 通过Java反射机制得到类的一些属性：继承的接口，父类，函数信息，成员信息，类型等
	Demo6();
	System.out.println("===============================================");

	//Demo7: 通过Java反射机制调用类中方法
	Demo7();
	System.out.println("===============================================");

	//Demo8: 通过Java反射机制获得类加载器
	Demo8();
	System.out.println("===============================================");

	}

	/**
	* Demo1: 通过Java反射机制得到类的包名和类名
	*/
	public static void Demo1()
	{
	Person person = new Person();
	System.out.println("Demo1: 包名: " + person.getClass().getPackage().getName() + "，"
	+ "完整类名: " + person.getClass().getName());
	}

	/**
	* Demo2: 验证所有的类都是Class类的实例对象
	* @throws ClassNotFoundException
	*/
	public static void Demo2() throws ClassNotFoundException
	{
	//定义两个类型都未知的Class , 设置初值为null, 看看如何给它们赋值成Person类
	Class<?> class1 = null;
	Class<?> class2 = null;

	//写法1, 可能抛出 ClassNotFoundException [多用这个写法]
	class1 = Class.forName("cn.lee.demo.Person");
	System.out.println("Demo2:(写法1) 包名: " + class1.getPackage().getName() + "，"
	+ "完整类名: " + class1.getName());

	//写法2
	class2 = Person.class;
	System.out.println("Demo2:(写法2) 包名: " + class2.getPackage().getName() + "，"
	+ "完整类名: " + class2.getName());
	}

	/**
	* Demo3: 通过Java反射机制，用Class 创建类对象[这也就是反射存在的意义所在]
	* @throws ClassNotFoundException
	* @throws IllegalAccessException
	* @throws InstantiationException
	*/
	public static void Demo3() throws ClassNotFoundException, InstantiationException, IllegalAccessException
	{
	Class<?> class1 = null;
	class1 = Class.forName("cn.lee.demo.Person");
	//由于这里不能带参数，所以你要实例化的这个类Person，一定要有无参构造函数哈～
	Person person = (Person) class1.newInstance();
	person.setAge(20);
	person.setName("LeeFeng");
	System.out.println("Demo3: " + person.getName() + " : " + person.getAge());
	}

	/**
	* Demo4: 通过Java反射机制得到一个类的构造函数，并实现创建带参实例对象
	* @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");
	//得到一系列构造函数集合
	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: 通过Java反射机制操作成员变量, 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: 修改属性之后得到属性变量的值：" + personNameField.get(obj));

	}


	/**
	* Demo6: 通过Java反射机制得到类的一些属性：继承的接口，父类，函数信息，成员信息，类型等
	* @throws ClassNotFoundException
	*/
	public static void Demo6() throws ClassNotFoundException
	{
	Class<?> class1 = null;
	class1 = Class.forName("cn.lee.demo.SuperMan");

	//取得父类名称
	Class<?> superClass = class1.getSuperclass();
	System.out.println("Demo6: SuperMan类的父类名: " + superClass.getName());

	System.out.println("===============================================");


	Field[] fields = class1.getDeclaredFields();
	for (int i = 0; i < fields.length; i++) {
	System.out.println("类中的成员: " + fields[i]);
	}
	System.out.println("===============================================");


	//取得类方法
	Method[] methods = class1.getDeclaredMethods();
	for (int i = 0; i < methods.length; i++) {
	System.out.println("Demo6,取得SuperMan类的方法：");
	System.out.println("函数名：" + methods[i].getName());
	System.out.println("函数返回类型：" + methods[i].getReturnType());
	System.out.println("函数访问修饰符：" + Modifier.toString(methods[i].getModifiers()));
	System.out.println("函数代码写法： " + methods[i]);
	}

	System.out.println("===============================================");

	//取得类实现的接口,因为接口类也属于Class,所以得到接口中的方法也是一样的方法得到哈
	Class<?> interfaces[] = class1.getInterfaces();
	for (int i = 0; i < interfaces.length; i++) {
	System.out.println("实现的接口类名: " + interfaces[i].getName() );
	}

	}

	/**
	* Demo7: 通过Java反射机制调用类方法
	* @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调用无参方法fly()：");
	Method method = class1.getMethod("fly");
	method.invoke(class1.newInstance());

	System.out.println("调用有参方法walk(int m)：");
	method = class1.getMethod("walk",int.class);
	method.invoke(class1.newInstance(),100);
	}

	/**
	* Demo8: 通过Java反射机制得到类加载器信息
	*
	* 在java中有三种类类加载器。[这段资料网上截取]

	1）Bootstrap ClassLoader 此加载器采用c++编写，一般开发中很少见。

	2）Extension ClassLoader 用来进行扩展类的加载，一般对应的是jre\lib\ext目录中的类

	3）AppClassLoader 加载classpath指定的类，是最常用的加载器。同时也是java中默认的加载器。
	*
	* @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: 类加载器类名: " + 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("超人会飞耶～～");
	}

	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("超人会走耶～～走了" + m + "米就走不动了！");
	}
	}
	interface ActionInterface{
	public void walk(int m);
	}