反射——获取成员变量

一时失言乱红尘 2023-08-17 16:08 145阅读 0赞

1、Class对象获取成员变量：

Class类的常用方法（获取Field对象）：

![1392562-20190821175801319-864958425.png][]

![1392562-20190821175828639-802621123.png][]

创建Person类：

package pers.reflect.person;
    
    public class Person {
    private String name;
    private int age;
    public String hobby;
    public String height;
    protected String sex;
    String address;
    
    public Person(){
        
    }
    public Person(String name,int age){
        this.name=name;
        this.age=age;
    }
    
    
    @Override
    public String toString() {
        return "Person [name=" + name + ", age=" + age + ", hobby=" + hobby
                + ", height=" + height + ", sex=" + sex + ", address=" + address
                + "]";
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    
    }

import java.lang.reflect.Field;
    
    import pers.reflect.person.Person;
    
    public class ReflectDemo {
    
        public static void main(String[] args) throws SecurityException,
                NoSuchFieldException, IllegalArgumentException,
                IllegalAccessException {
    
            Class c = Person.class;
            System.out.println("getFields()，获取公共的成员变量：");
            Field[] fields = c.getFields();
            for (Field field : fields) {
                System.out.println(field);
            }
    
            System.out.println("getField(),获取指定的公共的成员变量：");
    
            Field hobbyField = c.getField("hobby");
            System.out.println(hobbyField);
    
            System.out.println("getDeclaredFields()，获取所有的成员变量，与修饰符无关。");
    
            Field[] fields1 = c.getDeclaredFields();
            for (Field field : fields1) {
                System.out.println(field);
            }
    
            System.out.println("获取私有的指定的成员变量");
    
            Field nameField = c.getDeclaredField("age");
    
            System.out.println(nameField);
    
        }
    }

2、Field类的常用方法：

（1）返回变量的类型：

![1392562-20190821180208433-1601311468.png][]

（2）返回属性的名字：

![1392562-20190821180317944-395796861.png][]

import java.lang.reflect.Field;
    
    import pers.reflect.person.Person;
    
    
    public class ReflectDemo1 {
    public static void main(String[] args) {
        Class c = Person.class;
        System.out.println("getDeclaredFields()，获取所有的成员变量，与修饰符无关。");
        System.out.println(); Field[] fields1 = c.getDeclaredFields(); for (Field field : fields1) { System.out.println("成员变量："+field); System.out.println("属性的类型："+field.getType()); System.out.println("属性的名字："+field.getName()); System.out.println(); } } }

![1392562-20190821193729869-389260766.png][]

![1392562-20190821193900340-668220867.png][]

![1392562-20190821193927600-224754183.png][]

import java.lang.reflect.Field;
    
    import pers.reflect.person.Person;
    
    
    public class ReflectDemo2 {
    public static void main(String[] args) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
        Class c = Person.class;
        System.out.println("getField(),获取指定的公共的成员变量：");
        Field hobbyField = c.getField("hobby"); System.out.println(hobbyField); Person p=new Person(); Object value=hobbyField.get(p); System.out.println(value); hobbyField.set(p, "张可可"); System.out.println(p); System.out.println(); } }

![1392562-20190821194842629-1025039018.png][]

访问不是被public修饰的成员变量（要用暴力反射，否者无法访问）：

import java.lang.reflect.Field;
    
    import pers.reflect.person.Person;
    
    public class ReflectDemo3 {
        public static void main(String[] args) throws SecurityException,
                NoSuchFieldException, IllegalArgumentException,
                IllegalAccessException {
            Class c = Person.class;
            Field nameField = c.getDeclaredField("name");
            nameField.setAccessible(true);//暴力反射
            System.out.println(nameField); Person p = new Person(); Object value = nameField.get(p); System.out.println(value); nameField.set(p, "赵晓霞"); System.out.println(p); } }

setAccessible(true)；忽略权限修饰符的安全检查。

转载于:https://www.cnblogs.com/zhai1997/p/11390314.html

[1392562-20190821175801319-864958425.png]: /images/20230810/e60b394bfb4f4aafb7b5c995a3645f34.png
[1392562-20190821175828639-802621123.png]: /images/20230810/0b638051687540daa4ecc2a0bcb97b5f.png
[1392562-20190821180208433-1601311468.png]: /images/20230810/d6c89118db154c60a53e73f2061217cb.png
[1392562-20190821180317944-395796861.png]: /images/20230810/0c8ce7b1f7534a8880e1f05c53aae67e.png
[1392562-20190821193729869-389260766.png]: /images/20230810/7f5eaaeac7a14790a117a3767888828b.png
[1392562-20190821193900340-668220867.png]: /images/20230810/3ec68660e53d41e4a354a155bb5c218c.png
[1392562-20190821193927600-224754183.png]: /images/20230810/7a78e7a3e734456e83e3d188ebd15bfd.png
[1392562-20190821194842629-1025039018.png]: /images/20230810/9ed7298d1c35404388277de10fa1c3d7.png