JDK dynamic proxy interface agent

 Before understanding jdk agency, we need to know what is a dynamic proxy? Dynamic proxy can do it?

　　There are many proxy object (such as a star agent), can achieve real object function, added the foundation is still the real object of the new features, to ensure that the real object has not been modified in real life. And jdk dynamic proxy to implement this principle and probably the same.

Summary:

1. It requires the presence of abstract objects, all actions

2. The real object implements the abstract objects of all functions

3. By Proxy class, create a proxy object, call the proxy method

4. In invoke InvocationHandler have chosen not to amend the existing modify real object method or method acting.

Abstract role

Package Penalty for com.it.proxy; 
/ ** 
 abstract roles: the definition of the function 
 * / 
public  interface Star { 
    / ** 
     sing 
     @param Song
      * / 
    void Sing (String Song); 
    / ** 
     performances 
     @param Money
      * / 
    void ACT ( int Money); 
}

 

Real role

Star is only responsible for singing, filming.

Package Penalty for com.it.proxy; 
/ ** 
 real character 
 * / 
public  class SuperStar the implements Star { 
    @Override 
    public  void Sing (String Song) { 
        System.out.println ( "star sang:" + Song); 
    } 
    @Override 
    public  void ACT ( int Money) { 
        System.out.println ( "star appearance fees filming:" + Money); 
    } 
}

 

jdk dynamic proxy role

Stars help agency fees, see the money does not meet the full requirements of the star.

Package com.it.proxy; 


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

public  class Fans { 

public  static  void main (String [] args) { 
　　/ * 
　　use JDK dynamic proxy, creating a proxy object 
　　parameter 1: class loader 
　　parameter 2: All implemented interfaces 
　　parameter 3: interface method invocation, Star interface each method will be called a
　　 * / 
　　Star S2 = (Star) the Proxy.newProxyInstance ( 
　　　　s1.getClass (). getClassLoader (), 
　　　　new new class [] {Star. class },
　　new new of InvocationHandler () {
 / * 
for each method enhancements
Parameter 1: proxy object can not be called directly, or recursion
Parameter 2: The method of each object, such as: sing () act (), each method will be called a 
parameter 3: the parameter passing method, such as: song 
Return Value: returns the value of the method invocation 
 
　　}* / 
@Override 
public Object invoke (Object Proxy, method, method, Object [] args) throws the Throwable {
　　// If the method is performed, it is determined whether or not less than 1000, not less than if performed, or call the original method 
　　String methodName = method.getName ();
　　IF ( "ACT" .equals (methodName)) {
　　// get the value of the parameter presentation 
　　int Money = ( int ) args [0 ];
　　IF (Money <1000 ) { 
　　　　System.out.println ( "low cost, not performed" );
 　　return  null ; 
} 
　　// other cases it calls the real object original method 
　　return Method.invoke (s1, args); // parameters of a real object, the method 
　　} 
}); 
   
　　// please fans of their favorite star singing appearances, filming 
　　s2.sing ( "because you're so beautiful" ); 
　　// low cost does not satisfy 
　　s2.act ( 500 ); 

　　} 
}