programmer-guide/src/docs/asciidoc/common-libraries.adoc

:virgo-name: Virgo
:version: 3.7.0.RC01

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:tomcat-product-name: Virgo for Apache Tomcat
:tomcat-product-name-short: VTS
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anchor:common-libraries[]

== Working with Common Enterprise Libraries

Common Libraries

anchor:common-libraries-hibernate[]

=== Working with Hibernate

anchor:common-libraries-hibernate-import[]

==== Importing Hibernate

Hibernate uses CGLIB to dynamically create subclasses of your entity types at
runtime. To guarantee that Hibernate and CGLIB can correctly see the types,
you must add an `Import-Library` or `Import-Bundle` for the Hibernate library or bundle
into any bundle that uses Hibernate directly.

Additionally, if other bundles in your application contain types to be persisted by Hibernate, then be sure to specify the `import-scope` directive of the `Import-Bundle` header in the bundle that uses Hibernate directly.  The `import-scope` directive tells {tomcat-product-name} to implicitly import the bundle into all other bundles that make up the application; this ensures that bundles that indirectly depend on the generated Hibernate classes have access to them, but you do not have to explicitly update their `Import-Bundle` header, ensuring modularity.  For example:

[source,txt]
----
Import-Bundle: com.springsource.org.hibernate;version="[3.2.6.ga,3.2.6.ga]";import-scope:=application
----

The `import-scope` directive works only for the bundles in a scoped application (PARs or plans.)

anchor:common-libraries-datasources[]

=== Working with DataSources

Many `DataSource` implementations use the `DriverManager`
class which is incompatible with typical OSGi class loading semantics. To get around this,
use a `DataSource` implementation that does not rely on
`DriverManager`. Versions of the following
`DataSources` that are known to work in an OSGi environment are available in the
{ebr}.

* http://build.eclipse.org/rt/virgo/ivy/bundles/release/org.eclipse.virgo.mirrored/org.apache.commons.dbcp/[Apache Commons DBCP]
* SimpleDriverDataSource available in http://build.eclipse.org/rt/virgo/ivy/bundles/release/org.eclipse.virgo.mirrored/org.springframework.jdbc/[Spring JDBC] 2.5.5 and later

anchor:common-libraries-weaving-instrumentation[]

=== Weaving and Instrumentation

When using a library that performs bytecode weaving or instrumentation, such as AspectJ,
OpenJPA or EclipseLink, any types that are woven must be able to see the library doing
the weaving. This is accomplished by adding an `Import-Library` for the
weaving library into all bundles that are to be woven.

Weaving is often used by JPA implementations to transform persisted types. When using a
JPA provider that uses load-time weaving, an `Import-Library` for the
provider is needed in the bundles containing the persisted types.

anchor:common-libraries-tld[]

=== JSP Tag Libraries

When using tag libraries within a WAR or WAB, be sure to include an `Import-Bundle`
or `Import-Library` for the tag library bundle(s). This will ensure that your WAR or WAB
can see the TLD definition and implementing types. For example, to use the Apache implementation of JSTL,
add the following to your bundle's `/META-INF/MANIFEST.MF`:

[source,txt]
----
Import-Bundle: com.springsource.org.apache.taglibs.standard;version="1.1.2"
----

`Import-Package` can also be used but it is tedious to add all the imports as there are
typically lots of tld definitions in a bundle providing them.