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java反射机制简单实例

技术2022-05-11  3


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package com.yemaozi.reflect; import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; public class ReflectTest {     /**     * 通过java的反射机制获取类的所有属性和方法     */     public void test1() {         try {             Class c = Class.forName("com.yemaozi.reflect.Customer");             System.out.println("属性:");             Field f[] = c.getDeclaredFields();             for (int i = 0; i < f.length; i++) {                 System.out.println(f[i].getName());             }             System.out.println("方法:");             Method m[] = c.getDeclaredMethods();             for (int i = 0; i < m.length; i++) {                 System.out.println(m[i].toString());             }         } catch (Throwable e) {             System.err.println(e);         }     }     /**     * 通过java的反射机制动态修改对象的属性     * @param o     */     public void test2(Customer o) {         try {             Class c = o.getClass();             //getMethod方法第一个参数指定一个需要调用的方法名称,第二个参数是需要调用方法的参数类型列表,如无参数可以指定null,该方法返回一个方法对象              Method sAge = c.getMethod("setAge", new Class[] { int.class });             Method gAge = c.getMethod("getAge", null);             Method sName = c.getMethod("setName", new Class[] { String.class });             //动态修改Customer对象的age             Object[] args1 = { new Integer(25) };             sAge.invoke(o, args1);             //动态取得Customer对象的age             Integer AGE = (Integer) gAge.invoke(o, null);             System.out.println("the Customer age is: " + AGE.intValue());             //动态修改Customer对象的name             Object[] args2 = { new String("李四") };             sName.invoke(o, args2);         } catch (Throwable e) {             System.err.println(e);         }     }     /**     * 通过java的反射机制做一个简单对象的克隆     * @param o     * @return     */     public Object test3(Customer o) {         Object o2 = null;         try {             Class c = o.getClass();             //通过默认构造方法创建一个新的对象             o2 = c.getConstructor(new Class[] {}).newInstance(                     new Object[] {});             Field fields[] = c.getDeclaredFields();             for (int i = 0; i < fields.length; i++) {                 Field field = fields[i];                 String fieldName = field.getName();                 String firstLetter = fieldName.substring(0, 1).toUpperCase();                 // 获得和属性对应的getXXX()方法的名字                 String getMethodName = "get" + firstLetter + fieldName.substring(1);                 // 获得和属性对应的setXXX()方法的名字                 String setMethodName = "set" + firstLetter + fieldName.substring(1);                 // 获得和属性对应的getXXX()方法                 Method getMethod = c.getMethod(getMethodName, new Class[] {});                 // 获得和属性对应的setXXX()方法                 Method setMethod = c.getMethod(setMethodName, new Class[] { field.getType() });                 // 调用原对象的getXXX()方法                 Object value = getMethod.invoke(o, new Object[] {});                 // 调用拷贝对象的setXXX()方法                 setMethod.invoke(o2, new Object[] { value });             }         } catch (Throwable e) {             System.err.println(e);         }         return o2;     }     public static void main(String[] args) throws Exception {         ReflectTest t = new ReflectTest();         t.test1();         Customer customer = new Customer();         customer.setAge(20);         customer.setName("张三");         System.out.println("调用前name: " + customer.getName());         System.out.println("调用前age: " + customer.getAge());         t.test2(customer);         System.out.println("调用后name: " + customer.getName());         System.out.println("调用后age: " + customer.getAge());         Customer customer2 = (Customer)t.test3(customer);         System.out.println("克隆对象的name: " + customer2.getName());         System.out.println("克隆对象的age: " + customer2.getAge());     } } class Customer {     private long id;     private String name;     private int age;     public Customer() {     }     public Customer(String name, int age) {         this.name = name;         this.age = age;     }     public long getId() {         return id;     }     public void setId(long id) {         this.id = id;     }     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;     } } 运行结果: 属性: id name age 方法: public java.lang.String demo1.client.Customer.getName() public long demo1.client.Customer.getId() public void demo1.client.Customer.setName(java.lang.String) public void demo1.client.Customer.setAge(int) public int demo1.client.Customer.getAge() public void demo1.client.Customer.setId(long) 调用前name: 张三 调用前age: 20 the Customer age is: 25 调用后name: 李四 调用后age: 25 克隆对象的name: 李四 克隆对象的age: 25


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