Cannot start an OSGI bundle that embed spring boot in liferay 7 - spring

Question

I want to develop a standalone bundle that implement a service using spring boot and spring data jpa (without web).
The bundle aims to create a spring context to facilitate the creation of Repository, and in teh bundle activator, I create the spring boot application, get an implementation of service that use the injected repository and this service will be registered as an OSGI service.
The bundle will be deployed on Liferay 7 so there is no ready bundles to help exporting packages (for jpa ...), to make simpler the idea is to have a standalone bundle that embed all dependencies in the bundle classpath (no package to import from outside the bundle)
Is there any sample that can help ? and is that a good idea ?
The problem was, when trying to start the bundle, it fails with "Caused by: java.lang.ClassNotFoundException: org.osgi.framework.BundleActivator .."
The following classes are simplified sampel to demonstates the problem (normally it must be a separate bundle that define and export the api that will be implemented by the bundle in question, but in this sample this is a unique bundle with 4 classes)
1/ The bundle activator class
import java.util.Hashtable;
import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceRegistration;
import org.springframework.context.ApplicationContext;
public class Activator implements BundleActivator
{
#Override
public void start(BundleContext context) throws Exception
{
ApplicationContext springCtx = SpringFramework.getContext();
UserDao dao = springCtx.getBean(UserDao.class);
userDaoReg = bc.registerService(UserDao.class.getName(), dao, new Hashtable());
}
#Override
public void stop(BundleContext context) throws Exception
{
/** **/
}
}
2/ class to launch the spring boot application
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
#SpringBootApplication
public class SpringFramework {
private static ConfigurableApplicationContext context;
public static void main(String[] args) {
context = SpringApplication.run(SpringFramework.class);
}
public static ConfigurableApplicationContext getContext()
{
if (context == null) {
context = SpringApplication.run(SpringFramework.class);
}
return context;
}
}
3/ The UserDao to be registered as a service
import org.springframework.data.jpa.repository.JpaRepository;
public interface UserDao extends JpaRepository<User, Integer>
{
}
4/ and a simple JPA Entity class "User"
And these are dependencies and plugin used in the pom.xml
<dependencies>
<!--OSGI dependencies-->
<dependency>
<groupId>org.osgi</groupId>
<artifactId>org.osgi.core</artifactId>
<scope>provided</scope>
</dependency>
<!-- Spring -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!--persistence-api -->
<dependency>
<groupId>javax.persistence</groupId>
<artifactId>persistence-api</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>1.3.0.RELEASE</version>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.6</version>
<configuration>
<archive>
<manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.felix</groupId>
<artifactId>maven-bundle-plugin</artifactId>
<version>3.2.0</version>
<executions>
<execution>
<id>bundle-manifest</id>
<phase>process-classes</phase>
<goals>
<goal>manifest</goal>
</goals>
<configuration>
<instructions>
<Import-Package>!*</Import-Package>
<Bundle-Activator>hello.Activator</Bundle-Activator>
<Embed-Dependency>*</Embed-Dependency>
<!--<Embed-Transitive>true</Embed-Transitive>-->
</instructions>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
This is the generated manifest in the jar
Manifest-Version: 1.0
Bundle-SymbolicName: test-spring-boot-no-web
Archiver-Version: Plexus Archiver
Built-By: XXX
Bnd-LastModified: 1475774161783
Bundle-ManifestVersion: 2
Embed-Dependency: *
Require-Capability: osgi.ee;filter:="(&(osgi.ee=JavaSE)(version=1.8))"
Spring-Boot-Version: 1.3.0.RELEASE
Tool: Bnd-3.2.0.201605172007
Main-Class: org.springframework.boot.loader.JarLauncher
Embedded-Artifacts: org.osgi.core-6.0.0.jar;g="org.osgi";a="org.osgi.c
ore";v="6.0.0",slf4j-api-1.7.13.jar;g="org.slf4j";a="slf4j-api";v="1.
7.13",spring-boot-starter-1.3.0.RELEASE.jar;g="org.springframework.bo
ot";a="spring-boot-starter";v="1.3.0.RELEASE",spring-boot-starter-dat
a-jpa-1.3.0.RELEASE.jar;g="org.springframework.boot";a="spring-boot-s
tarter-data-jpa";v="1.3.0.RELEASE",persistence-api-1.0.2.jar;g="javax
.persistence";a="persistence-api";v="1.0.2",javax.transaction-api-1.2
.jar;g="javax.transaction";a="javax.transaction-api";v="1.2"
Export-Package: hello;version="1.0.0"
Bundle-Name: spring-boot-no-web
Bundle-Version: 1.0.0.SNAPSHOT
Bundle-ClassPath: .,org.osgi.core-6.0.0.jar,slf4j-api-1.7.13.jar,sprin
g-boot-starter-1.3.0.RELEASE.jar,spring-boot-starter-data-jpa-1.3.0.R
ELEASE.jar,persistence-api-1.0.2.jar,javax.transaction-api-1.2.jar
Bundle-Activator: hello.Activator
Start-Class: hello.SpringFramework
Created-By: Apache Maven Bundle Plugin
Build-Jdk: 1.8.0_101

Answer 1

I saw 2 questions in your post so I'll try to answer those:
Is there any sample that can help ?
I don't think so! What you are trying to do seems weird to me. See below for details.
... is that a good idea ?
You are saying you want "standalone bundle" that "will be deployed on Liferay 7"! It may be you just picked the wrong words but the way you state it, you are trying to have mutually exclusive things.
There is no such thing as "standalone bundle". I assume you mean standalone java application (executable Jar file that has the OSGi framework embedded). You can build such applications in a number of different ways. For example there is excellent tutorial how to do this from EnRoute. You can not however deploy such executable jar as it typically is not a OSGi bundle. While technically you can make it a bundle, you may run into all kinds of issues due to the embeded runtime and dependencies.
In Liferay 7 (and any outher product that has OSGi container) you can run a bundle in the runtime environment the product defines. The bundle must be resolvable at runtime. It may have all it's dependencies embedded but that defeats the purpose of modularity unless it provides something to outher bundles (which does not seem to be your case).
From that perspective what you are trying to do seems to be a bad idea. Moreover Spring Boot is a framework to build stand alone java applications and as such have it's own assumptions. Making it work inside an OSGi container is likely not a trivial task (if at all possible)
Perhaps better idea would be to have some bundles providing the business logic only. Then you could deploy those bundles in Liferay and laverage Liferay's capabilities to serve REST servces. You could use the exact same bundles to cunstruct standalone application that uses Spring or CXF or something else.
Notes about your code
your main class is org.springframework.boot.loader.JarLauncher. If you run this jar it will start Spring which likely will be totally unaware of OSGI runtime.
you have org.osgi.core-6.0.0.jar is your bundle's classpath with is basically the OSGi's runtime. This will cause issues if deployed into a OSGi runtime and my be the reason why you see
Caused by: java.lang.ClassNotFoundException: org.osgi.framework.BundleActivator ..