Java反射机制(Reflect)解析

 1 package bean;
 2 
 3 public class Person {
 4     private String name;
 5     private int age;
 6     public Person(){
 7         super();
 8     }
 9     public Person(String name,int age){
10         super();
11         this.name = name;
12         this.age = age;
13     }
14     public String getName() {
15         return name;
16     }
17     public void setName(String name) {
18         this.name = name;
19     }
20     public int getAge() {
21         return age;
22     }
23     public void setAge(int age) {
24         this.age = age;
25     }
26     
27     public static void function1(){
28         System.out.println("function1");
29     }
30     public void function2(){
31         System.out.println("function2");
32     }
33     public void function3(String s,int i){
34         System.out.println(s+":::"+i);
35     }
36     @SuppressWarnings("unused")
37     private void function4(){
38         System.out.println("function4");
39     }
40 }

 1 package reflect;
 2 
 3 import java.lang.reflect.Field;
 4 
 5 public class getFieldDemo {
 6     public static void main(String[] args) throws Exception {
 7         String className = "bean.Person";
 8         Class<?> c = Class.forName(className);
 9         
10         //获取私有字段
11         Field nameField = c.getDeclaredField("name");
12         Field ageField = c.getDeclaredField("age");
13         
14         //使用字段（使用之前我们需要一个该类对象）
15         Object obj = c.newInstance();
16         
17         //使用set()方法设置字段值
18         nameField.setAccessible(true);
19         ageField.setAccessible(true);//暴力访问
20         nameField.set(obj, "张三");
21         ageField.set(obj,20);
22         
23         //打印查看效果
24         System.out.println("获取到的字段：");
25         System.out.println("name:"+nameField);
26         System.out.println("age:"+ageField);
27         System.out.println("字段设置的值：name="+nameField.get(obj)+",age="+ageField.get(obj));
28     }
29 }

 1 package reflect;
 2 
 3 import java.lang.reflect.Method;
 4 
 5 public class getMethodDemo {
 6     public static void main(String[] args) throws Exception {
 7         String className = "bean.Person";
 8         Class<?> c = Class.forName(className);
 9         
10         //获取公共方法：
11         Method[] pubMethods = c.getMethods();
12         
13         //获取私有方法：
14         Method[] priMethods = c.getDeclaredMethods();
15         
16         
17         //获取单个方法：按方法名和参数获取
18         
19         //获取单个の静态方法：function1
20         Method staMethod = c.getMethod("function1",null);
21         //获取单个の无参数方法：function2
22         Method nullMethod = c.getMethod("function2",null);
23         //获取单个の有参数方法：function3
24         Method moreMethod = c.getMethod("function3",String.class,int.class);
25         //获取单个の私有方法：function4
26         Method priMethod = c.getDeclaredMethod("function4",null);
27         
28         //打印查看效果
29         System.out.println("[Person类的公共方法及父类方法:]");
30         for(Method m:pubMethods){
31             System.out.println(m);
32         }
33         System.out.println("[Person类的私有方法:]");
34         for(Method m:priMethods){
35             System.out.println(m);
36         }
37         System.out.println("[按方法名和参数类型获取的方法4个方法:]");
38         System.out.println(staMethod);
39         System.out.println(nullMethod);
40         System.out.println(moreMethod);
41         System.out.println(priMethod);    
42     }
43 }

 1 package reflect;
 2 
 3 import java.lang.reflect.Method;
 4 
 5 public class invokeDemo {
 6     public static void main(String[] args) throws Exception {
 7         String className = "bean.Person";
 8         Class<?> c = Class.forName(className);
 9         
10         //获取有参数的方法：function3
11         Method moreMethod = c.getDeclaredMethod("function3",String.class,int.class);
12         
13         //使用之前我们需要创建一个该类对象：
14         Object obj = c.newInstance();
15         moreMethod.setAccessible(true);//设置访问权限
16         Object value = moreMethod.invoke(obj,"李四",20);
17         
18         //打印查看效果
19         System.out.println(value);
20     }
21 }