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Re: Dynamic classpath

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  To: comp.lang.java.gui,comp.l
wizard of oz, 07.05.2008 10:41:
> I have a need to have a classpath that is determined by the set of jars 
> a user places into a directory.
> 
> By way of example, placing jar's into certain directories in a tomcat 
> web server will cause tomcat to include them into the web applications 
> class path. An example of this might be a charting package used by the 
> web app to generate charts.
> 
> In my specific example, I am building a query tool and I want to be able 
> to tell users to simply drop the JDBC drivers into a directory and my 
> app will "pick them up". Thus there would be no need to edit the classpath.
> 
> My target environment is Java 6.0
> 

You will need to use a URLClassLoader to load the driver(s) 

The only problem is then doing the connection as the DriverManager will refuse to use a driver that was loaded by a different classloader.

You have two options to resolve this:

1) use Connection.connect(String, Properties) directly (bypassing DriverManager) 
2) create a wrapper class that pretends to be a driver but delegates everything to the real instance (loaded by your own classloader). 

I am using option 1) without any problems.

Thomas

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Dynamic classpath "wizard of oz" <wizard.of.oz@THRWHITE.remove-dii-this> - 2011-04-27 15:45 +0000
  Re: Dynamic classpath "Thomas Kellerer" <thomas.kellerer@THRWHITE.remove-dii-this> - 2011-04-27 15:45 +0000
    Re: Dynamic classpath "wizard of oz" <wizard.of.oz@THRWHITE.remove-dii-this> - 2011-04-27 15:45 +0000
      Re: Dynamic classpath "Thomas Kellerer" <thomas.kellerer@THRWHITE.remove-dii-this> - 2011-04-27 15:45 +0000
  Re: Dynamic classpath "Roedy Green" <roedy.green@THRWHITE.remove-dii-this> - 2011-04-27 15:45 +0000
    Re: Dynamic classpath "Ian Shef" <ian.shef@THRWHITE.remove-dii-this> - 2011-04-27 15:45 +0000
      Re: Dynamic classpath "John B. Matthews" <john.b..matthews@THRWHITE.remove-dii-this> - 2011-04-27 15:45 +0000

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