反射调用成员属性

成员属性保存了一个对象的所有信息，通过反射可以实现成员属性的赋值与取值操作，本课程主要讲解了属性的直接操作，以及封装性取消等操作。

 

1.获取类中的成员属性信息

 1 package com.youtube.demo;
 2 
 3 import java.lang.reflect.field;;
 4 
 5 interface ichannelservice{
 6     public static final string name = "youtube";
 7 }
 8 abstract class absbase{
 9     protected static final string base = "www.youtube.com";
10     private string info = "hello, youtube";
11 }
12 class member extends absbase implements ichannelservice{
13     private string name;
14     private int age;
15 }
16 public class javareflectdemo {
17     public static void main(string[] args) {
18         class <?> cls = member.class;
19         {
20             field fields[] = cls.getfields();
21             for(field field:fields) {
22                 system.out.println(field);
23             }
24         }
25         system.out.println("----------------华丽的分割线------------------");
26         {
27             field fields[] = cls.getdeclaredfields();
28             for(field field:fields) {
29                 system.out.println(field);
30             }
31         }
32     }
33 }

运行结果：

public static final java.lang.string com.youtube.demo.ichannelservice.name
----------------华丽的分割线------------------
private java.lang.string com.youtube.demo.member.name
private int com.youtube.demo.member.age

 

2.反射操作成员属性内容：

 1 package com.facebook.demo;
 2 import java.lang.reflect.field;
 3 class member{
 4     private string name;
 5 }
 6 public class javareflectdemo {
 7     public static void main(string[] args) throws exception {
 8         class<?> cls = member.class;
 9         object obj = cls.getdeclaredconstructor().newinstance();
10         field namefield = cls.getdeclaredfield("name");
11         namefield.setaccessible(true);//解除封装
12         namefield.set(obj, "小李老师");
13         system.out.println(namefield.get(obj));
14     }
15 }

运行结果：

小李老师

如果不解除封装，会抛如下异常：

exception in thread "main" java.lang.illegalaccessexception: class com.facebook.demo.javareflectdemo cannot access a member of class com.facebook.demo.member with modifiers "private"
    at java.base/jdk.internal.reflect.reflection.newillegalaccessexception(reflection.java:355)
    at java.base/java.lang.reflect.accessibleobject.checkaccess(accessibleobject.java:639)
    at java.base/java.lang.reflect.field.checkaccess(field.java:1075)
    at java.base/java.lang.reflect.field.set(field.java:778)
    at com.facebook.demo.javareflectdemo.main(javareflectdemo.java:11)

 

3.获取指定属性类型：

 1 package com.facebook.demo;
 2 import java.lang.reflect.field;
 3 class member{
 4     private string name;
 5 }
 6 public class javareflectdemo {
 7     public static void main(string[] args) throws exception {
 8         class<?> cls = member.class;
 9         object obj = cls.getdeclaredconstructor().newinstance();
10         field namefield = cls.getdeclaredfield("name");
11         system.out.println(namefield.gettype().getname());
12         system.out.println(namefield.gettype().getsimplename());
13     }
14 }

运行结果：

java.lang.string
string