Providing global libraries for all Java EE applications
You can provide global libraries that can be used by any Java™ EE application. You do this by putting the JAR files for those libraries in a global library directory, then specifying use of global libraries in the class loader configuration for each application. However, the global libraries cannot be used by other applications, for example, by OSGi applications.
About this task
Under the user directory specified by using the environment
variable WLP_USER_DIR, there are the following locations
in which you can place global libraries:
- ${shared.config.dir}/lib/global
- ${server.config.dir}/lib/global
Attention: If you use global libraries, you are advised also to configure a
<classloader> element for every application. The servlet specification requires
applications to share the global library class loader in their class loader parent chain. This
breaks the separation of class loaders for each application that is otherwise possible. So,
applications are more likely to have long-lasting effects on classes loaded in Liberty and on each other, and class space
consistency issues are more likely to arise between applications, especially as features are added
and removed from a running server. None of these considerations apply for applications that specify
a <classloader> element in their configuration, because they maintain this
separation.
Example
In the following example, an application called Scholar is configured to use a common library called Alexandria, and also to use the global library.
In
the server.xml file, or an included file, enable
the global library for an application by adding the following code:
<application id="" name="Scholar" type="ear" location="scholar.ear">
<classloader apiTypeVisibility="spec" commonLibraryRef="Alexandria, global" />
</application>
The settings for the global library
can also be configured explicitly, as a library element with the special
ID global. For example:
<library id="global">
<fileset dir="/path/to/folder" includes="*.jar" />
</library>