Java反射--MonkeyKing

1. 获取类

    Class<?> perClazz = Class.forName("reflect.Person");
    System.out.println("perClazz: " + perClazz);

    Class<?> perClazz1 = Person.class;
    System.out.println("perClazz1: " + perClazz1);

    Person per = new Person();
    Class<?> perClazz3 = per.getClass();
    System.out.println("perClazz3: " + perClazz3);

2. 获取类中的参数

    //获取自己以及父类的public参数
    Field[] fields = clazz.getFields();
    for (Field f : fields) {
        System.out.println(f);
    }

    //获取自己的所有参数
    Field[] fieldsDeclared = clazz.getDeclaredFields();
    for (Field f : fieldsDeclared) {
        System.out.println(f);
    }

3. 获取类中的方法

    // 本类和父类中的public的方法(包括public/private/protect 返回类型 函数全名)
    Method[] methods = perClazz.getMethods();
    for (Method m : methods) {
        System.out.println(m);
    }

    //获取自己所有的方法
    Method[] methods = clazz.getDeclaredMethods();
    for (Method m : methods) {
        System.out.println(m);
    }

4. 获取构造函数

    /*
     * 包装类和基本属性不一样
     * 
     * 传入参数类型
     * 传入参数，用构造函数实例化对象
     * 
     * */
    Constructor constructor = clazz.getConstructor(int.class);
    Object o = constructor.newInstance(1234);
    Person per = (Person)o;

5. 实例化对选

    //创建一个对象
    Person p = (Person) clazz.newInstance();
    p.interfaceMethod();

    /*
     * 包装类和基本属性不一样
     * 
     * 传入参数类型 传入参数，用构造函数实例化对象
     * 
     */
     //没有传入参数就写null
    Constructor constructor = clazz.getConstructor(int.class);
    Object o = constructor.newInstance(1234);
    Person per = (Person) o;
    System.out.println(per.getId());

    //获取配置文件
    Properties prop = new Properties();
    prop.load(new FileReader("class.txt"));
    String classname = prop.getProperty("classname");
    String methodname = prop.getProperty("methodname");
    /*
     * classname=reflect.Student 
     * methodname=sayHi
     */
    Class<?> perClazz = Class.forName(classname);
    method = perClazz.getMethod(methodname);
    //用制定的对象执行该方法
    method.invoke(perClazz.newInstance());

6. 万能get set方法

public class PropertyUtil {
    public static void setProperty(Object obj, String propertyName, Object value) throws Exception{
        Class clazz = obj.getClass();
        Field field = clazz.getDeclaredField(propertyName);
        field.setAccessible(true);
        field.set(obj, value);
    }
    
    public static Object getProperty(Object obj, String propertyName) throws Exception {
        Class clazz = obj.getClass();
        Field field = clazz.getDeclaredField(propertyName);
        field.setAccessible(true);
        Object o = field.get(obj);
        return o;
    }
}
//==================================================================
    执行方法
//==================================================================
    Person person = new Person();
    PropertyUtil.setProperty(person, "id", 222);
    System.out.println(person.getId());
    PropertyUtil.setProperty(person, "name", "mk");
    Object obj = PropertyUtil.getProperty(person, "name");
    System.out.println(obj);

7. 测试

    ArrayList<Integer> list = new ArrayList<>();
    list.add(123);
    list.add(321);

    Class listClazz = list.getClass();
    method = listClazz.getMethod("add", Object.class);
    method.invoke(list, "lalala");
    System.out.println(list);