Chapter 11. Deploying a Plain JAR

Abstract

An alternative method of deploying applications into Apache Karaf is to use plain JAR files. These are usually libraries that contain no deployment metadata. A plain JAR is neither a WAR, nor an OSGi bundle.

If the plain JAR occurs as a dependency of a bundle, you must add bundle headers to the JAR. If the JAR exposes a public API, typically the best solution is to convert the existing JAR into a bundle, enabling the JAR to be shared with other bundles. Use the instructions in this chapter to perform the conversion process automatically, using the open source Bnd tool.

For more information on the Bnd tool, see Bnd tools website.

11.1. Converting a JAR Using the wrap Scheme

Overview

You have the option of converting a JAR into a bundle using the wrap: protocol, which can be used with any existing URL format. The wrap: protocol is based on the Bnd utility.

Syntax

The wrap: protocol has the following basic syntax: 

wrap:LocationURL

The wrap: protocol can prefix any URL that locates a JAR. The locating part of the URL, LocationURL, is used to obtain the plain JAR and the URL handler for the wrap: protocol then converts the JAR automatically into a bundle.

Note

The wrap: protocol also supports a more elaborate syntax, which enables you to customize the conversion by specifying a Bnd properties file or by specifying individual Bnd properties in the URL. Typically, however, the wrap: protocol is used just with the default settings.

Default properties

The wrap: protocol is based on the Bnd utility, so it uses exactly the same default properties to generate the bundle as Bnd does.

Wrap and install

The following example shows how you can use a single console command to download the plain commons-logging JAR from a remote Maven repository, dynamically convert it into an OSGi bundle, and then install it and start it in the OSGi container: 

karaf@root> bundle:install -s wrap:mvn:commons-logging/commons-logging/1.1.1

Reference

The wrap: protocol is provided by the Pax project, which is the umbrella project for a variety of open source OSGi utilities. For full documentation on the wrap: protocol, see the Wrap Protocol reference page.