JDK dynamic proxy to call methods in the interceptor

1. JDK can generate a proxy for the instance that implements the interface. Therefore, first create an interface.

// Interface person
Package cn.edu. HLD;

Public interface person
{
Public void Info ();
Public void run ();
}
2. To implement dynamic proxy later, an implementation class of the person interface is provided.

// Class personimpl. Java
Package cn.edu. HLD;

Public class personimpl implements person
{

Public void Info ()
{
// Todo auto-generated method stub
System. Out. println ("I am thtwin ");

}
Public void run ()
{
// Todo auto-generated method stub
System. Out. println ("I want to run faster! ");
}
}
3. Implement the core interceptor class when a method is called before or after the corresponding interceptor method is executed. As to which object to intercept, it must be reflected through subsequent operations.

// Personintercepter. Java
Package cn.edu. HLD;

Public class personintercepter
{
Public void Method1 ()
{
System. Out. println ("method_1 is executed! ");
}
Public void method2 ()
{
System. Out. println ("method_2 is executed! ");
}
}
4. To let the interceptor know the target object to be intercepted and the method to be executed, create a class that implements the interface invocationhandler In the JDK reflection system.

// Proxyhandler. Java
Package cn.edu. HLD;

Import java. Lang. Reflect. invocationhandler;
Import java. Lang. Reflect. method;

Public class proxyhandler implements invocationhandler
{
Private object target;
Private personintercepter Pi = new personintercepter ();
Public object invoke (Object proxy, method, object [] ARGs)
Throws throwable
{
Object result = NULL;
If (method. getname (). Equals ("info "))
{
Pi. Method1 ();
Result = method. Invoke (target, argS );
Pi. method2 ();
}
Else
{
Result = method. Invoke (target, argS );
}
Return result;
}
Public void settarget (object target)
{
This.tar get = target;
}
}
5. To generate a proxy object based on the target object, you should also create a proxy factory.

// Myproxyfactory. Java
Package cn.edu. HLD;

Import java. Lang. Reflect. proxy;

Public class myproxyfactory
{
Public static object getproxy (object target)
{
Proxyhandler handler = new proxyhandler ();
Handler. settarget (target );
Return proxy. newproxyinstance (personimpl. Class. getclassloader ()
, Target. getclass (). getinterfaces (), Handler );
}
}
6. Implementation of the main program.

// Testperson. Java
Package cn.edu. HLD;

Public class testperson
{
Public static void main (string ARGs [])
{
Person targetperson = new personimpl ();
Person = NULL;
Object proxy = myproxyfactory. getproxy (targetperson );
If (proxy instanceof Person)
{
Person = (person) proxy;
}
Person.info ();
Person. Run ();
}
}
7. Run the command directly in myeclipse. The result is as follows:

Method_1 is executed!
I'm thtwin.
Method_2 is executed!
I want to run faster!

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