Java反射《二》获取构造器

Posted 2020-10-06 溪山晴雪

 1 package com.study.reflect;
 2 
 3 import java.lang.reflect.Constructor;
 4 import java.lang.reflect.InvocationTargetException;
 5 
 6 /**
 7  * 通过类来反射出构造器。
 8  * @ClassName: ConstructorDemo 
 9  * @author BlueLake
10  * @date 2015年8月13日 下午5:16:07
11  */
12 public class ConstructorDemo {
13 
14     public static void main(String[] args) throws NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
15 
16         Class c = Student.class;
17         
18         //getConstructors()public修饰的构造方法
19         Constructor[] cons = c.getConstructors();
20         for(Constructor con:cons){
21             System.out.println(con);
22             /*
23              *  public com.study.reflect.Student(java.lang.String,int)
24                 public com.study.reflect.Student()
25              */
26         }
27         
28         System.out.println("---------------------------------");
29         
30         //getDeclaredConstructors()包括私有的方法
31         Constructor[] cons2 = c.getDeclaredConstructors();
32         for(Constructor con:cons2){
33             System.out.println(con);
34             /*
35              * private com.study.reflect.Student(java.lang.String)
36                 public com.study.reflect.Student(java.lang.String,int)
37                 public com.study.reflect.Student()
38              */
39         }
40         System.out.println("------****************-----------");
41         //获取指定参数的构造器
42         Constructor one = c.getConstructor(int.class);
43         System.out.println(one);//public com.study.reflect.Student(int)
44         Class[] cls = one.getParameterTypes();
45         for(Class cl:cls){
46             System.out.println(cl);//int
47             System.out.println(cl.getName());//int
48             System.out.println(cl.getSimpleName());//int
49         }
50         
51         Constructor two  = c.getDeclaredConstructor(String.class,int.class);
52         Class[] cls2 = two.getParameterTypes();
53         for(Class cl:cls2){
54             //输出类class标识和类全名。
55             System.out.println(cl);//class java.lang.String
56             //输出参数的类全名
57             System.out.println(cl.getName());//java.lang.String
58             //输出参数的类简化名
59             System.out.println(cl.getSimpleName());//String
60         }
61         
62         //通过参数数组来获得构造器
63         Class[] params = new Class[2];
64         params[0] = String.class;
65         params[1] = int.class;
66         Constructor three = c.getDeclaredConstructor(params );
67         
68         
69         /**
70          * 通过获得的构造器来创建对象
71          */
72         Object objone = one.newInstance(18);
73         if(objone instanceof Student){
74             Student stu = (Student)objone;
75             System.out.println(stu.getAge());
76         }
77         
78         Object objtwo = two.newInstance("项羽",27);
79         if(objtwo instanceof Student){
80             Student stu = (Student)objtwo;
81             System.out.println(stu.getName()+"..."+stu.getAge());//项羽...27
82         }
83         
84         Object objthree = three.newInstance("曹操",56);
85         if(objthree instanceof Student){
86             Student stu = (Student)objthree;
87             System.out.println(stu.getName()+"..."+stu.getAge());//曹操...56
88         }
89     }
90 }