The principle of dynamic proxies

1, 2 define an interface, the definition of a class that implements the interface 3, the use of proxy objects to obtain a dynamic method, and a method to enhance the solid object by three different methods (enhanced parameters, return value enhancement, body enhancement method) 
cn.hopetesting.proxy Package ; 

/ ** 
* @author newcityman 
* @date 2019/9/13 - 15:22 
* / 
public interface SaleComputer { 
 public String Sale ( Double Money) ; 
public void Show () ; 
}

cn.hopetesting.proxy Package ; 

/ ** 
* @author newcityman 
* @date 2019/9/13 - 15:24 
* / 
public class Lenovo the implements SaleComputer { 

 @Override public String Sale ( Double Money) { the System. Out.println ( "It took" + Money + "yuan to buy a Lenovo computer .....") ; return "Lenovo" ; } @Override public void Show () { System. out.println ( "show off computer") ; } }
 




 
 

cn.hopetesting.proxy Package ; 

Import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer ; 

Import java.lang.reflect.InvocationHandler ; 
Import the java.lang.reflect.Method ; 
Import the java.lang.reflect.Proxy ; 

/ ** 
* @author newcityman 
* @date 2019/9/13 - 15:34 
* / 
public class ProxyTest { 
 public static void main (String [] args) { 
 //. 1, to create a real object 
Lenovo Lenovo = new new Lenovo ( ) ; // 2, Lenovo enhanced dynamic proxy objects / * * three parameters * 1, class loader: the real object .getClass () getClassLoader (). * 2, an array of interfaces: the real object .getClass () getInterfaces ().
 
 



* 3, the processor: of InvocationHandler new new () 
* * / 
. SaleComputer proxy_lenovo = (SaleComputer) the Proxy 'newProxyInstance (lenovo.getClass () getClassLoader (). , Lenovo.getClass () The getInterfaces (). , Of InvocationHandler new new () { 
 / * * 
* 
* @param proxy proxy object 
* @param method the method of the proxy object called, is encapsulated as an object 
* @param args when the strip method with the proxy object, the actual parameters passed 
* @return * @throws the Throwable * / @Override public Object Invoke (Object Proxy , Method, Method , Object [] args) throws the Throwable {
 

 
 
 /*System.out.println ( "dynamic method is performed the proxy"); 
System.out.println (method.getName ()); 
System.out.println (args [0]); * / IF (Method. . getName () the equals ( "Sale") ) { //. 1, enhancement parameters Double Money = ( Double) args [ 0] ; Money Money * = 0.85 ; . the System Out.println ( "pick car") ; // use The real object calls the method String obj = (String) Method.invoke ( lenovo , Money) ; System. out.println ( "free shipping .....") ; // return value enhancement obj = obj + "_ removable hard disk " ; return obj ; } the else { Object obj = Method.invoke(

 
 
 


 


 



lenovo, args);
 return obj;
 }
 }
 });

 //2、调用方法
 String computer = proxy_lenovo.sale(5000);
 System.out.println(computer);

 /* proxy_lenovo.show();*/


 }
}