Classloader: A Processing Method for Jar

/**

* @ Author Tom

*

* This class is used to test the dynamic loading of classes in jar files.

*/

Public class jarloader

{

Private Static void test (string [] ARGs) throws exception

{

Object OBJ = new myappclassloader (""). loadclass ("testccl"). newinstance ();

System. Out. println ("loaded? "+ OBJ );

}

Public static void main (string [] ARGs)

{

Try

{

Test (ARGs );

}

Catch (exception E)

{

E. printstacktrace ();

}

}

}

Public class myappclassloader extends urlclassloader

{

String m_jarfile = "E: \ javaproject \ classloadertest \ bin \ test. Jar ";

Public myappclassloader (string jarfile)

{

Super (new URL [0]);

If (jarfile! = NULL & jarfile. Length ()> 0)

{

This. m_jarfile = jarfile;

}

}

 

Public class loadclass (string name) throws classnotfoundexception

{

System. Out. println ("myappclassloader loadclass !! ");

Try

{

URL url = new java. Io. File (m_jarfile). tourl ();

Return new urlclassloader (new URL [] {URL}). loadclass (name );

}

Catch (exception E)

{

E. printstacktrace ();

}

Return super. loadclass (name );

}

}

Public class testccl

{

Public testccl ()

{

System. Out. println ("CCL run !!! ");

// New BB ();

Try

{

Class. forname ("BB"). newinstance ();

// New BB ();

}

Catch (exception E)

{

E. printstacktrace ();

}

}

Public static void main (string [] ARGs)

{



}

}

Public Class BB

{

Public BB ()

{

System. Out. println ("BB construct ");

}

}

The result is

Myappclassloader loadclass !!

CCL run !!!

Bb construct

Loaded? Testccl @ 93dee9

"CCL run !!!" Why does this sentence appear only once? According to the principle that class. forname ("BB") uses myappclassloader, why is it not the loadclass method,

No.