1.Filed:封装了字段的信息，获取字段

    @Test
    public void test4() throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        Class clazz = Class.forName("reflect.Person");

       //获取字段,仅能获取public,包括自己和父类的
        Field[]  fields = clazz.getFields();
        for (int i = 0; i < fields.length; i++) {
            System.out.println(fields[i]);
        }

        //仅能获取当前类的字段包括私有的
        Field[]  fields1 = clazz.getDeclaredFields();
        for (int i = 0; i < fields1.length; i++) {
            System.out.println(fields1[i]);
        }

        //获取指定名字的字段
        Field field = clazz.getField("age");
        System.out.println(field);

        Person person=  new Person(1,"xiaoming",1);
        //获取指定对象指定Field的值
        Object obj = field.get(person);
         //输出字段age的值
        System.out.println(obj);

         //设置指定对象指定字段的值
        field.set(person,2);
        System.out.print(person.getAge());

        //若属性字段是私有的，name是私有的
        Field field1 = clazz.getDeclaredField("name");
        System.out.print(field1);
        field1.setAccessible(true);//设置可访问
        Object obj1 = field1.get(person);
        //输出字段age的值
        System.out.println(obj1);
    }

2.获取构造器，构造器在实际中使用较少

   //获取构造器
    @Test
    public void test() throws ClassNotFoundException {
        Class clazz = Class.forName("reflect.Person");
        Constructor[] cons = clazz.getConstructors();
        for(Constructor con:cons){
            System.out.println(con);
        }

    }

3.注解

（1）创建注解

（2）注解方法

/*
*注解
 */
@Retention(RetentionPolicy.RUNTIME)//运行时可见
@Target(value={ElementType.METHOD})//范围：方法上面
public @interface AgeValidator {
    public int max();
    public int min();

}

（3）对象的字段设置

    @AgeValidator(min=0,max=100)
    public void setAge(int age) {
        this.age = age;
    }

（3）测试

 //注解
    @Test
    public void testAnnotation() throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException {
        //假设要给对象的某一字段设置一个范围例如：Person中的age的范围为0-100
        //1.创建注解
        Class clazz = Class.forName("reflect.Person");
        Object obj  = clazz.newInstance();
        Method method = clazz.getDeclaredMethod("setAge",int.class);
        int age = 200;
        //2.获取注解
        Annotation annotation = method.getAnnotation(AgeValidator.class);
        if(annotation!=null){
            //进行判断
//            if(age>100||age<0){
//                throw  new RuntimeException("年龄不合法");
//            }
            //通过注解的方法设置
            if(((AgeValidator) annotation).max()<age||((AgeValidator) annotation).min()<age){
                throw  new RuntimeException("年龄不合法");
            }
        }
        method.invoke(obj,age);


    }