Is it possible to integrate OSGi with Spring Data?

Question

I'm currently working on an OSGi application running under apache Karaf that uses JPA and QueryDSL.

I was wondering if I could use Spring Data with QueryDSL instead of the current approach.

The reason for this is that I find Spring repositories to be quite useful and having a template for NoSQL database accesses might be useful in the future.

I have tried to start a normal spring application without a web context with OSGi but I get a ClassNoutFoundException when it tries to load the applicationContext.xml or the ApplicationContext.class.

I don't want to use Spring DM since it is discontinued.

Basically the sole reason for wanting to try this integration is for the Spring Repositories, but if you think this is not necessary please tell me. Any information regarding how to achive this or if it's ok to persue this would be more than welcome.

Thank you

Update

I've managed to make spring work by starting the application context with org.eclipse.gemini.blueprint.context.support.OsgiBundleXmlApplicationContext. The applicationContext is exported in OSGi as a service and I can get all the beans that I need by calling it.

The problem I'm having right now is that when I declare <jpa:repositories base-package="x.y.z" /> I get the following exception:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor#0' defined in URL [bundle://251.13:0/META-INF/spring/applicationContext.xml]: Initialization of bean failed; nested exception is java.lang.IllegalStateException: No persistence exception translators found in bean factory. Cannot perform exception translation.
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:527)[185:org.springframework.beans:3.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)[185:org.springframework.beans:3.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)[185:org.springframework.beans:3.1.4.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)[185:org.springframework.beans:3.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)[185:org.springframework.beans:3.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)[185:org.springframework.beans:3.1.4.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1109)[187:org.springframework.context:3.1.4.RELEASE]
    at org.eclipse.gemini.blueprint.context.support.AbstractDelegatedExecutionApplicationContext.registerBeanPostProcessors(AbstractDelegatedExecutionApplicationContext.java:502)[193:org.eclipse.gemini.blueprint.core:1.0.0.RELEASE]
    at org.eclipse.gemini.blueprint.context.support.AbstractDelegatedExecutionApplicationContext.registerBeanPostProcessors(AbstractDelegatedExecutionApplicationContext.java:451)[193:org.eclipse.gemini.blueprint.core:1.0.0.RELEASE]
    at org.eclipse.gemini.blueprint.context.support.AbstractDelegatedExecutionApplicationContext$4.run(AbstractDelegatedExecutionApplicationContext.java:306)[193:org.eclipse.gemini.blueprint.core:1.0.0.RELEASE]
    at org.eclipse.gemini.blueprint.util.internal.PrivilegedUtils.executeWithCustomTCCL(PrivilegedUtils.java:85)[193:org.eclipse.gemini.blueprint.core:1.0.0.RELEASE]
    at org.eclipse.gemini.blueprint.context.support.AbstractDelegatedExecutionApplicationContext.completeRefresh(AbstractDelegatedExecutionApplicationContext.java:290)[193:org.eclipse.gemini.blueprint.core:1.0.0.RELEASE]
    at org.eclipse.gemini.blueprint.extender.internal.dependencies.startup.DependencyWaiterApplicationContextExecutor$CompleteRefreshTask.run(DependencyWaiterApplicationContextExecutor.java:137)[194:org.eclipse.gemini.blueprint.extender:1.0.0.RELEASE]
    at java.lang.Thread.run(Thread.java:662)[:1.6.0_37]
Caused by: java.lang.IllegalStateException: No persistence exception translators found in bean factory. Cannot perform exception translation.
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.detectPersistenceExceptionTranslators(PersistenceExceptionTranslationInterceptor.java:142)[195:org.springframework.transaction:3.1.4.RELEASE]
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.<init>(PersistenceExceptionTranslationInterceptor.java:79)[195:org.springframework.transaction:3.1.4.RELEASE]
    at org.springframework.dao.annotation.PersistenceExceptionTranslationAdvisor.<init>(PersistenceExceptionTranslationAdvisor.java:70)[195:org.springframework.transaction:3.1.4.RELEASE]
    at org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor.setBeanFactory(PersistenceExceptionTranslationPostProcessor.java:103)[195:org.springframework.transaction:3.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeAwareMethods(AbstractAutowireCapableBeanFactory.java:1475)[185:org.springframework.beans:3.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1443)[185:org.springframework.beans:3.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)[185:org.springframework.beans:3.1.4.RELEASE]

As a JPA provider I'm using OpenJPA. The entityManagerFactory is a service which I can get by using the blueprint. I think I need to reference it in <jpa:repositories base-package="x.y.z" />, but how do I do that since the applicationContext.xml is read by spring and not the blueprint?

I would really appreciate any hint in the right direction.

Thank you

Answer 1

Use Querydsl-SQL directly in your code and

• it will work well within OSGi as it does not use class loading, weaving, enhancing, caching and other tricks that sound really good but causes chaos
• your code will run much faster than with any of the "cache-enhanced" JPA engines
• others will be able to understand your code (not like JPA Criteria API queries)
• you will know exactly what SQL commands run on the Database Server that minimizes problem-solving time
• your code will be as database independent as with any ORM tool

Do not use Spring, spring-data, JPA and other monoholitic technologies together with OSGi as

• they were designed to work within monoholitic systems where everything is in one application context, not in separate bundles
• by using these technologies together with OSGi you will spend most of your time to fix bugs like this and looking for workarounds

People who argue with this, already spent lots of time on finding such workarounds. They managed to implement some business logic. They hope that they now truly found workarounds for every conceptual issue and they do not have to spend the same amount of work next time. They are in a bidding fee auction. Be honest guys! Somewhere deep you know I am right ;-).

I am saying this with the experience that I

• tried the perfect stack based on Hibernate and Don't repeat the DAO article of IBM (much before Spring-Data hype began). Twice
• wrote hibernate-osgi-adapter for Hibernate 4.1.x
• Re-implemented the complete JPA chapter of OSGi Enterprise specification