动态代办是运用反射和字节码的手艺,在运行期建立指定接口或类的子类(动态代办)以及其实例对象的手艺,经由过程这个手艺能够无侵入性的为代码举行加强(引荐:Java教程)
Proxy:Proxy是一切动态代办的父类,它供应了一个静态要领来建立动态代办的class对象和实例;
InvocationHandler:每一个动态代办实例都有一个关联的InvocationHandler。 在代办实例上挪用要领时,要领挪用将被转发到InvocationHandler的invoke要领;
1.java 动态代办完成
//java的代办形式必须有一个interface的接口要领 public interface ItemService { void sayHello(); } public class ItemServiceImpl implements ItemService { @Override public void sayHello() { System.out.println("hello world~"); } } //代办类 public class MyInvocationHandler implements InvocationHandler { private Object realObject; public void setRealObject(Object realObject) { this.realObject = realObject; } public Object getRealObject() { return realObject; } public MyInvocationHandler(Object realObject){ super(); this.realObject=realObject; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { System.out.println("before running ~~"); Object ret=method.invoke(realObject,args); System.out.println("after running ~~~"); return ret; } } // 完成类 public class main { public static void main(String[] args) { ItemService itemService=new ItemServiceImpl(); MyInvocationHandler handler=new MyInvocationHandler(itemService); ItemService proxy= (ItemService) Proxy.newProxyInstance(itemService.getClass().getClassLoader(),itemService.getClass().getInterfaces(),handler); proxy.sayHello(); } }
2.CGLIB的完成体式格局
CGLIB(Code Generation Library)是一个基于ASM的字节码生成库,它许可我们在运行时对字节码举行修正和动态生成。CGLIB经由过程继续体式格局完成代办;
Enhancer:来指定要代办的目的对象、现实处置惩罚代办逻辑的对象,终究经由过程挪用create()要领获得代办对象,对这个对象一切非final要领的挪用都邑转发给MethodInterceptor;
MethodInterceptor:动态代办对象的要领挪用都邑转发到intercept要领举行加强;
//1.须要引入 <dependency> <groupId>cglib</groupId> <artifactId>cglib</artifactId> <version>3.2.6</version> </dependency> //2.要领 public class ItemServiceImpl { void sayHello(String name) { System.out.println("hello world~"+name); } } //3.cglib代办完成类 public class MyInterceptor implements MethodInterceptor { private Object realObject; public void setRealObject(Object realObject) { this.realObject = realObject; } public Object getRealObject() { return realObject; } public MyInterceptor(Object realObject){ this.realObject=realObject; } @Override public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable { System.out.println("before running ~~"); System.out.println(method); System.out.println(Arrays.toString(objects)); Object ret=methodProxy.invoke(realObject,objects); System.out.println("after running ~~"); return ret; } } //4.完成类 public class main { public static void main(String[] args) { ItemServiceImpl itemService=new ItemServiceImpl(); Enhancer enhancer=new Enhancer(); enhancer.setSuperclass(ItemServiceImpl.class); enhancer.setCallback(new MyInterceptor(itemService)); ItemServiceImpl imp= (ItemServiceImpl) enhancer.create(); imp.sayHello("张三"); } }
总结:
JDK原生动态代办是Java原生支撑的,不须要任何外部依靠,然则它只能基于接口举行代办;
CGLIB经由过程继续的体式格局举行代办,不管目的对象有无完成接口都能够代办,然则没法处置惩罚final的状况
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