java反射机制简单实例

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