通过一个例子学习反射的使用

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public class Test {    /**     * 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);    }}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);}
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