Invalid property ‘cacheTarget’ of bean class [org.springframework.osgi.service.exporter.support.OsgiServiceFactoryBean]

Okay, so I’ve lost so much time on this incredibly stupid issue, and Google wasn’t of much help that I thought I’d blog about it as a memo for myself and for others.

here’s the setup : I’ve created an osgi bundle (using PDE new plugin wizard), created a class (implementing an interface) and tried to export it as an OSGi service using Spring DM.

I used Spring IDE tooling to generate my bundle’s context xml files (I tend to follow the Spring DM best practices in separating the bundle’s context in 2 xml files, one for the regular Spring setup, the other for OSGi interactions).

Anyway, the first xml file simply declares a Spring bean :

<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xsi:schemalocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

	<bean id="todoListsServiceImpl" class="org.dynaresume.blueprint.todo.service.impl.TodoListsServiceImpl"></bean>
</beans>

Whereas the second one simply exports that bean as an OSGi service :

<beans xmlns:osgi="http://www.springframework.org/schema/osgi" 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.xsd
	http://www.springframework.org/schema/osgi http://www.springframework.org/schema/osgi/spring-osgi-2.0-m1.xsd">

	<osgi:service ref="todoListsServiceImpl" interface="org.dynaresume.blueprint.todo.service.ITodoListsService">

</osgi:service></beans>

It can’t get simpler than this. Even worse, I’ve been working with OSGi and Spring DM on a rather big project at work for more than a year now, and yet, this simple example invariantly failed at runtime with this stacktrace :

927674 [SpringOsgiExtenderThread-5] ERROR org.springframework.osgi.extender.internal.activator.ContextLoaderListener – Application context refresh failed (OsgiBundleXmlApplicationContext(bundle=org.dynaresume.blueprint.todo.service.impl, config=osgibundle:/META-INF/spring/*.xml))
org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘org.springframework.osgi.service.exporter.support.OsgiServiceFactoryBean#0′: Error setting property values; nested exception is org.springframework.beans.NotWritablePropertyException: Invalid property ‘cacheTarget’ of bean class [org.springframework.osgi.service.exporter.support.OsgiServiceFactoryBean]: Bean property ‘cacheTarget’ is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?
[...]
at java.lang.Thread.run(Thread.java:619)
Caused by: org.springframework.beans.NotWritablePropertyException: Invalid property ‘cacheTarget’ of bean class [org.springframework.osgi.service.exporter.support.OsgiServiceFactoryBean]: Bean property ‘cacheTarget’ is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?
[...]
… 18 more

This drove me mad for 3 days : I’ve tried many (stupid) things, like trying out different versions of Spring DM, or Spring (2.5.6[ε|.A|.SEC01]) to no avail.

But tonight, after coming back from a 4 days vacation, I was able to track down the cause of this issue : it’s caused by the usage of and old version of Spring DM’s osgi schema. If you look back at the second xml file’s source, you can see :

http://www.springframework.org/schema/osgi http://www.springframework.org/schema/osgi/spring-osgi-2.0-m1.xsd

This schema’s version declares a cache-target xml attribute, and while I didn’t use it in my xml, a default value was inferred and the Spring bean creation facility didn’t find it to it’s liking and thus the stacktrace listed above.

Simply changing the xsd to :

http://www.springframework.org/schema/osgi http://www.springframework.org/schema/osgi/spring-osgi-1.2.xsd

Fixes the issue.

I feel awful right now.
Based on Mirko’s comment, I’ve updated this post to specify the xsd schema to use instead of relying on the generic name.

Pascal and/or Angelo : if you read this, then you’ll understand that I won’t be able to finish the task we talked about in a week as I promised ! (and don’t you dare make fun of me, this kind of shit can happen to anybody )