java反射的简单例子

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