classloader ?

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ganjaman - 06 Feb 2006 10:59 GMT

hello.
sorry for my bad english... (i'm italian)
Problem
i've to build and application that uses plugin in the following way:
1.the core starts.
2.the core checks for the presences of plugin classe
3.the core call the plugin's constructor and methods.

how can i resolve this problem ?
thank in advance

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Lothar Kimmeringer - 06 Feb 2006 11:04 GMT

> i've to build and application that uses plugin in the following way:
> 1.the core starts.
> 2.the core checks for the presences of plugin classe
> 3.the core call the plugin's constructor and methods.
>
> how can i resolve this problem ?

Using an URLClassLoader and Reflection.

Regards, Lothar

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ganjaman - 06 Feb 2006 11:42 GMT

> Using an URLClassLoader and Reflection.

Reflection is the key
thanks a lot

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Thomas Fritsch - 06 Feb 2006 11:58 GMT

> Problem
> i've to build and application that uses plugin in the following way:

You should make it a requirement that all the plug-in classes
(*) implement a common interface that you specify
(*) have a public no-arguments-constructor.

public interface Plugin {
... method declarations
}
The concrete plug-ins would be implementations of that interface
public class MyPlugin implements Plugin {
public MyPlugin() { } // constructor
... method implementions
}

> 1.the core starts.
> 2.the core checks for the presences of plugin classe

Get the class names of all plug-ins somehow.
For each className either do
Class pluginClass = Class.forName(pluginClassName);
or
Class pluginClass = yourClassLoader.loadClass(pluginClassName);

> 3.the core call the plugin's constructor and methods.

Plugin plugin = (Plugin) pluginClass.newInstance();
plugin.method(...);

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Roedy Green - 06 Feb 2006 14:18 GMT

>i've to build and application that uses plugin in the following way:
>1.the core starts.
>2.the core checks for the presences of plugin classe
>3.the core call the plugin's constructor and methods.

You might have a look at how Sun solves the problem with roll your own
CharSets, fonts, L&F and JCE, locale resource bundles

See http://mindprod.com/jgloss/encoding.html
http://mindprod.com/jgloss/font.html
http://mindprod.com/jgloss/laf.html
http://mindprod.com/jgloss/jce.html
http://mindprod.com/jgloss/internationalisation.html

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Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

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classloader ?

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