Java 反射 调用 demo

Posted 2020-10-18

基础类.供demo反射练习

 1 package fanshe;
 2 
 3 public class Person {
 4     public String name;
 5     private String age;
 6     private int p;
 7     public Person() {};
 8     public Person(String name, String age) {
 9         super();
10         this.name = name;
11         this.age = age;
12     }
13     private Person(String name, String age,int p) {
14         super();
15         this.name = name;
16         this.age = age;
17         this.p = p;
18     }
19     public String getName() {
20         return name;
21     }
22     @Override
23     public String toString() {
24         return "Person [name=" + name + ", age=" + age + "]" + "p -"+ p;
25     }
26     public void setName(String name) {
27         this.name = name;
28     }
29     public String getAge() {
30         return age;
31     }
32     public void setAge(String age) {
33         this.age = age;
34     }
35 }

反射demo类

 1 package fanshe;
 2 
 3 import java.lang.reflect.Constructor;
 4 import java.lang.reflect.Field;
 5 import java.lang.reflect.InvocationTargetException;
 6 import java.lang.reflect.Method;
 7 
 8 public class demo1 {
 9 
10     public static void main(String[] args) {
11         // TODO Auto-generated method stub
12         try {
13             d_3();
14         } catch (Exception e) {
15             // TODO: handle exception
16             e.printStackTrace();
17         }
18     }
19     
20     private static void d_1() {
21         Person p = new Person();
22         Class  c = p.getClass();
23     
24     }
25     
26     private static void d_2() {
27         Class  c =  Person.class;
28           System.out.println(c);
29     }
30     private static void d_3() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException {
31         Class  c = Class.forName("fanshe.Person");
32         
33         //--------------------------//
34         Constructor con = c.getConstructor(); //获得 空参数的构造器 public
35         Object o= con.newInstance(); //运行获取到的构造方法
36         System.out.println(o.toString());
37         
38         //--------------------------//
39         Constructor con2 = c.getConstructor(String.class,String.class); //获得带有参数的构造方法 public
40         Object o2 = (Person)con2.newInstance("a","22");
41         System.out.println(o2.toString());
42         
43         //--------------------------//
44         
45         Constructor con3 = c.getDeclaredConstructor(String.class,String.class,int.class); //获得带有参数的构造方法 private
46         con3.setAccessible(true);
47         Object o3 = (Person)con3.newInstance("a","22",14);
48         System.out.println(o3.toString());
49         
50         //--------------------------//
51         Object tmp_obj = c.newInstance();
52         Field f_name = c.getField("name");//获得成员变量 public
53         f_name.set(tmp_obj, "abc"); //设置变量
54         System.out.println(tmp_obj);
55         
56         //--------------------------//
57         Field f_age = c.getDeclaredField("age");//获得成员变量 public
58         System.out.println(f_age);
59         
60         //--------------------------//
61         Method m_getName = c.getMethod("getName"); //获得类函数无参数 public
62         Object o1 = m_getName.invoke(tmp_obj); //运行getName方法.返回值 反给obj
63         System.out.println(o1);
64         
65         //--------------------------//
66         Method m_setName = c.getMethod("setName",String.class);
67         m_setName.invoke(tmp_obj,"abcdqweqwe");
68         System.out.println(tmp_obj.toString());
69     }
70 }

通过反射.绕开泛型

1 ArrayList<String> arr = new ArrayList<String>();
2 arr.add("a");
3 Class carr = arr.getClass();
4 Method arr_add = carr.getMethod("add",Object.class);
5 arr_add.invoke(arr, 1);
6 arr_add.invoke(arr, 2);
7 arr_add.invoke(arr, 3);
8 arr_add.invoke(arr, 4);
9 System.out.println(arr);