Create OSGI-Spring Project with Maven

Introduction

This document is for developers who knows Java, but not familiar with new technologies such as Spring or OSGi.

Your First Spring-OSGi Project

In this section, you will learn how to create simple Spring + OSGi project with Maven.

Setup

For this tutorial, you need to install the following software:

• Java 5/6
• Maven 2.0.9 or later

Installation of Maven is simple. All you have to do is just download, unzip, and set path to the maven directory.

Procedure

• Open the terminal. Make sure maven is correctly installed on your system.

  kono$ mvn -version
  Maven version: 2.0.9
  Java version: 1.5.0_16
  OS name: "mac os x" version: "10.4.11" arch: "i386" Family: "unix"

• Create new project.

  mvn org.ops4j:maven-pax-plugin:create-project -DgroupId=org.cytoscape -DartifactId=osgi-sample

  cd to osgi-sample directory (this is your project name).

• Add SpringSource Enterprise Bundle Repository to your project.

  mvn pax:add-repository -DrepositoryId=com.springsource.repository.bundles.external -DrepositoryURL=http://repository.springsource.com/maven/bundles/external

  This means maven trying to find required bundles in the SpringSource's repository if they does not exist in the central maven repository.

• Import infrastructure bundles. In our case, we need Spring Framework and Spring Dynamic Modules to run our bundles. So we need to import those bundles.

  mvn pax:import-bundle -DgroupId=org.springframework.osgi -DartifactId=spring-osgi-extender -Dversion=1.1.2 "-DimportTransitive" "-DwidenScope"

• Now create your first bundle. Last two options creates some templates for developing bundles running with Spring DM and simple tests.

  mvn pax:create-bundle -Dpackage=org.cytoscape.sample "-Dspring" "-Djunit=4.4"

• Compile, test, and run your project.

mvn clean install pax:provision

• Type ps. Then you can see something like this:

  -> ps
  START LEVEL 6
     ID   State         Level  Name
  [   0] [Active     ] [    0] System Bundle (1.4.1)
  [   1] [Active     ] [    5] spring-osgi-extender (1.1.2)
  [   2] [Active     ] [    5] spring-osgi-core (1.1.2)
  [   3] [Active     ] [    5] SLF4J Jakarta Commons Logging Over SLF4J Binding (1.5.0)
  [   4] [Installed  ] [    5] SLF4J API (1.5.0)
  [   6] [Active     ] [    5] spring-osgi-io (1.1.2)
  [   7] [Active     ] [    5] spring-aop (2.5.5)
  [   8] [Active     ] [    5] spring-beans (2.5.5)
  [   9] [Active     ] [    5] spring-context (2.5.5)
  [  10] [Active     ] [    5] spring-core (2.5.5)
  [  11] [Active     ] [    5] spring-test (2.5.5)
  [  12] [Active     ] [    5] AOP Alliance API (1.0.0)
  [  13] [Active     ] [    5] Backport Util Concurrent (3.1.0)
  [  14] [Active     ] [    5] Apache Log4J (1.2.15)
  [  15] [Active     ] [    5] Java Messaging System API (1.1.0)
  [  16] [Active     ] [    5] Java Transaction API (1.1.0)
  [  17] [Active     ] [    5] org.cytoscape.sample (1.0.0.SNAPSHOT)
  [  18] [Active     ] [    1] osgi.compendium (4.1.0.build-200702212030)
  [  19] [Active     ] [    1] OPS4J Pax Logging - API (1.3.0)
  [  20] [Active     ] [    1] OPS4J Pax Logging - Service (1.3.0)
  [  21] [Active     ] [    1] Apache Felix Shell Service (1.0.2)
  [  22] [Active     ] [    1] Apache Felix Shell TUI (1.0.2)
  -> 

  Bundles are running on Apache Felix. You can dynamically start/stop these bundles.

  [  17] [Active     ] [    5] org.cytoscape.sample (1.0.0.SNAPSHOT)

  This is your bundle. All other bundles are infrastructure bundles which provides functions like shell, AOP, Spring bean creation, etc. To stop your bundle, type

  stop 17

  where 17 is your bundle ID. Type ps again.

  START LEVEL 6
     ID   State         Level  Name
  [   0] [Active     ] [    0] System Bundle (1.4.1)
  [   1] [Active     ] [    5] spring-osgi-extender (1.1.2)
  [   2] [Active     ] [    5] spring-osgi-core (1.1.2)
  [   3] [Active     ] [    5] SLF4J Jakarta Commons Logging Over SLF4J Binding (1.5.0)
  [   4] [Installed  ] [    5] SLF4J API (1.5.0)
  [   6] [Active     ] [    5] spring-osgi-io (1.1.2)
  [   7] [Active     ] [    5] spring-aop (2.5.5)
  [   8] [Active     ] [    5] spring-beans (2.5.5)
  [   9] [Active     ] [    5] spring-context (2.5.5)
  [  10] [Active     ] [    5] spring-core (2.5.5)
  [  11] [Active     ] [    5] spring-test (2.5.5)
  [  12] [Active     ] [    5] AOP Alliance API (1.0.0)
  [  13] [Active     ] [    5] Backport Util Concurrent (3.1.0)
  [  14] [Active     ] [    5] Apache Log4J (1.2.15)
  [  15] [Active     ] [    5] Java Messaging System API (1.1.0)
  [  16] [Active     ] [    5] Java Transaction API (1.1.0)
  [  17] [Resolved   ] [    5] org.cytoscape.sample (1.0.0.SNAPSHOT)
  [  18] [Active     ] [    1] osgi.compendium (4.1.0.build-200702212030)
  [  19] [Active     ] [    1] OPS4J Pax Logging - API (1.3.0)
  [  20] [Active     ] [    1] OPS4J Pax Logging - Service (1.3.0)
  [  21] [Active     ] [    1] Apache Felix Shell Service (1.0.2)
  [  22] [Active     ] [    1] Apache Felix Shell TUI (1.0.2)
  -> 

  You can see your bundle is no longer active. Let's start it again

  start 17

  Now you can see lots of log messages. If you read those messages carefully, you can see some interesting ones:

  [SpringOsgiExtenderThread-4] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'myExampleBean'
  [SpringOsgiExtenderThread-4] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating instance of bean 'myExampleBean'
  [SpringOsgiExtenderThread-4] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Eagerly caching bean 'myExampleBean' to allow for resolving potential circular references
  [SpringOsgiExtenderThread-4] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Finished creating instance of bean 'myExampleBean'

  This is the message from Spring Dynamic Modules infrastructure bundles. It recognizes your bundle, and read settings, and automatically create bean named myExampleBean.

Inside Your Bundle

Let's look into the code.

kono$ cd org.cytoscape.sample
kono$ ls -l
total 16
-rw-r--r--   1 kono  kono   201 Mar 11 17:36 osgi.bnd
-rw-r--r--   1 kono  kono  2656 Mar 11 17:36 pom.xml
drwxr-xr-x   4 kono  kono   136 Mar 11 17:36 src
drwxr-xr-x   6 kono  kono   204 Mar 11 17:54 target

This is the basic directory structure of Spring-OSGi project created by maven. In the following directory, you can see two XML files

These two XML files defines your beans and OSGi Services'.

• bundle-context.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

  <!-- regular spring configuration file defining the beans for this
       bundle. We've kept the osgi definitions in a separate 
       configuration file so that this file can easily be used
       for integration testing outside of an OSGi environment -->

  <bean name="myExampleBean" class="org.cytoscape.sample.internal.ExampleBeanImpl" />

</beans>

This is the file to define your beans. In this example, only one bean named myExampleBean is defined. This entry creates an instance of org.cytoscape.sample.internal.ExampleBeanImpl and that's all Spring does in this example.

• bundle-context-osgi.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:osgi="http://www.springframework.org/schema/osgi"
  xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
                      http://www.springframework.org/schema/osgi http://www.springframework.org/schema/osgi/spring-osgi-1.0.xsd">

</beans>