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From: =?UTF-8?B?SsO2cmc=?= Schaible <joerg.schaible@swisspost.com>
Subject: Re: [Commons Wiki] Update of "MavenAndClasspath" by sebbapache
Date: Tue, 29 Jul 2014 12:12:46 +0200
Organization: Swiss Post Solutions
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References: <20140729055954.82839.26306@eos.apache.org>
 <4004b033a1c0f6277b162778cf9c8c67@scarlet.be>
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Gilles wrote:

>> [...]
>>
>> == Java classloader ==
>>
>> The Java runtime system only allows a single instance of a class to
>> exist in a given classloader.
>> Classes are uniquely identified using the package name and class
>> name.
>>
>> For example, the class {{{Utils}}} in the package
>> {{{org.apache.commons.example}}} can only appear once in a
>> classloader.
>>
>> The classloader uses the classpath to find the classes needed by an
>> application.
>>
>> If the classpath contains more than one jar which contains the above
>> Utils class, then the JVM will load only one of the instances.
>>
>> If the class instances in the different jars are identical, then this
>> is not a problem, but if there are two different versions of the
>> class, the classloader may choose the wrong one. And different JVMs
>> may process the classpath in a different order.
> 
> Is that correct?
> 
> Excerpt from
> http://docs.oracle.com/javase/8/docs/technotes/tools/unix/classpath.html:
> -----
> The order in which you specify multiple class path entries is
> important.
> The Java interpreter will look for classes in the directories in the
> order they appear in the class path variable.
> -----
> 
> Gilles
> 
>> [...]

If your jars are in the WEB-INF/lib folder of a web application ... do you 
know in which sequence the application server adds those jars to the 
classpath ??

- Jörg


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