View source for FAQ How can I share a JAR among various plug-ins?

Suppose that plug-in <i>A</i> and plug-in <i>B</i> both use <tt>xmlparser.jar</tt>. 
In your workspace are two projects (for <i>A</i> and <i>B</i>), each containing a 
copy of the <tt>xmlparser.jar</tt> library. This is clearly not ideal: 
Two copies of the JAR are loaded at runtime, and classes from those
JARs will not be compatible with each other, as they are loaded by
different class loaders. (You will get a <tt>ClassCastException</tt> if you
try to cast a type from one library into a type from the other library.)



Declaring <tt>xmlparser.jar</tt> as an external JAR does not work, as there is no easy
way during deployment of your plug-ins to manipulate your plug-in&#146;s classpath
so that they can see the library. The best way to share libraries is to create a 
new plug-in that wraps the library you want to share.



Declare a new plug-in, <i>C</i>, to contain the library JAR, and make
both plug-in <i>A</i> and plug-in <i>B</i> dependent on plug-in <i>C</i>. 
Make sure that plug-in <i>C</i> exports its library so other 
plug-ins can see it:
<pre>
   &lt;runtime&gt;
      &lt;library name=&quot;xmlParserAPIs.jar&quot;&gt;
         &lt;export name=&quot;*&quot;/&gt;
      &lt;/library&gt;
   &lt;/runtime&gt;
</pre>



When you deploy these three plug-ins, they will all share the 
same library. Note that in some situations, sharing libraries between 
plug-ins is not possible.  If two plug-ins require 
different or incompatible versions of the same library, they have no 
choice but to each have a copy of the library.






== See Also: ==


[[FAQ_What_is_the_classpath_of_a_plug-in%3F]]


[[FAQ_How_do_I_add_a_library_to_the_classpath_of_a_plug-in%3F]]

<hr><font size=-2>This FAQ was originally published in [http://www.eclipsefaq.org Official Eclipse 3.0 FAQs]. Copyright 2004, Pearson Education, Inc. All rights reserved. This text is made available here under the terms of the [http://www.eclipse.org/legal/epl-v10.html Eclipse Public License v1.0].</font>