Java如何通过反射获取对象的属性和值

public class Person {
    private String firstName;
    private String lastName;
    
    public Person(String firstName, String lastName) {
	    this.firstName = firstName;
	    this.lastName = lastName;
    }
}

public static void main(String[] args) {
        Person p1 = new Person("xiao ming", "huang");
        getField(p1);
    }
    public static void getField(Object obj) {
        Class<?> clazz = obj.getClass();
        Field[] field = clazz.getDeclaredFields();
        for (Field f : field) {
            f.setAccessible(true);
            try {
                System.out.println("属性名:" + f.getName()+",属性值:" + f.get(obj).toString());
                // ...
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
    }

Person p = new Person();
Class clazz = p.getClass();

Class clazz = Person.class;

Class clazz = Class.forNmae("com.user.entery.Person")//类的全路径包括包名

```Class three = Class.forName("com.nasi.demo.entity.User");
//获取全部方法
Method[] declaredMethods = three.getDeclaredMethods();

Class three = Class.forName("com.nasi.demo.entity.User");
//获取全部构造方法
Constructor[] declaredConstructors = three.getDeclaredConstructors();

Class three = Class.forName("com.nasi.demo.entity.User");
Field[] declaredFields = two.getDeclaredFields();

public class Calculator{ 
     
    public double add(double score1,double score2){
        return score1 + score2;
    }
     
    public void print(){
        System.out.println("OK");
    }
     
    public static double mul(double score1,double score2){
        return score1 * score2;
    }
}

public class CalculatorTest {
 
    public static void main(String[] args) throws Exception {
        //通过类的.class属性获取
        Class<Calculator> clz = Calculator.class;
        //或者通过类的完整路径获取,这个方法由于不能确定传入的路径是否正确,这个方法会抛ClassNotFoundException
//      Class<Calculator> clz = Class.forName("test.Calculator");
        //或者new一个实例,然后通过实例的getClass()方法获取
//      Calculator s = new Calculator();
//      Class<Calculator> clz = s.getClass();

        //1. 获取类中带有方法签名的mul方法,getMethod第一个参数为方法名,第二个参数为mul的参数类型数组
        Method method = clz.getMethod("mul", new Class[]{double.class,double.class});
        //invoke 方法的第一个参数是被调用的对象,这里是静态方法故为null,第二个参数为给将被调用的方法传入的参数
        Object result = method.invoke(null, new Object[]{2.0,2.5});
        //如果方法mul是私有的private方法,按照上面的方法去调用则会产生异常NoSuchMethodException,这时必须改变其访问属性
        //method.setAccessible(true);//私有的方法通过发射可以修改其访问权限
        System.out.println(result);//结果为5.0
        
        //2. 获取类中的非静态方法
        Method method_2 = clz.getMethod("add", new Class[]{double.class,double.class});
        //这是实例方法必须在一个对象上执行
        Object result_2 = method_2.invoke(new Calculator(), new Object[]{2.0,2.5});
        System.out.println(result_2);//4.5
        
        //3. 获取没有方法签名的方法print
        Method method_3 = clz.getMethod("print", new Class[]{});
        Object result_3 = method_3.invoke(new Calculator(), null);//result_3为null,该方法不返回结果    
    }
}