返射

返射

public class Test001 {

    @Test
    public void test1() throws  Exception  {
        getObjectClass();
        getObjectStaticClass();
        getForNameClass();
        getMethodFromClass();
    }

    /**
     * 1获取对象字节码
     *
     * Object中的getClass
     */
    public void getObjectClass() {
        Person p = new Person();
        Class cp = p.getClass();
        System.out.println(cp);
    }

    /**
     * 2、获取对象字节码
     *
     * 静态方法.class
     */
    public void getObjectStaticClass() {
        Class cp = Person.class;
        System.out.println(cp);
    }

    /**
     * 3、获取对象字节码
     * java.lang中的
     * forName
     */
    public void getForNameClass() throws  Exception  {
        /**
         * 空参
         */
        String className="vo.Person";
        Class cp=Class.forName(className);



        Object obj =  cp.newInstance();
        if(obj instanceof Person){
            System.out.println("obj"+obj);
        }
        System.out.println(cp);
        /**
         * 指定参数
         */

        Constructor constructor=  cp.getConstructor(String.class,int.class,Date.class);

        Object obj1 =  constructor.newInstance("丘小燕",123,new Date());

        Field field =  Class.forName(className).getDeclaredField("name");

        /**
         * 对私有字段取消返回检查
         */
        field.setAccessible(true);

        field.set(obj1,"丘大燕");

        System.out.println(field.get(obj1));


    }


    public void getMethodFromClass() throws Exception {
        String className="vo.Person";
        Class clazz =  Class.forName(className);
        /**
         * 取所有公有的方法
         */
//        Method[] methods =  clazz.getMethods();

        /**
         * 取所有的方法
         */
        Method[] methods =  clazz.getDeclaredMethods();

        Stream.of(methods).forEach((e)->{
            System.out.println(e);
        });


        Method method =  clazz.getDeclaredMethod("show",String.class,int.class,Date.class);
        method.setAccessible(true);
        method.invoke(clazz.newInstance(),"丘燕燕",111,new Date());

    }


}

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