CODEWITHSUNDEEP
javaspringhibernatespring-mvc
Rob
Rob

Reputation: 4224

Error in Spring bean injection : leads to a NullPointerException

I am totally new to Spring framework, bean injections etc, and working on a project organized in many sub-projects about it.

In the commons subproject, containing all Entities, DAOs, DS, I have a MyDS class implementing IMyDS and containing its EntityManager and DAO :

@PersistenceContext(unitName="myPersistenceUnit")
private EntityManager entityManager;

@Autowired
@Qualifier("myDAO")
private IMyDAO mainDao;

Then, I am trying to call this class from the Web part of my project, like this:

@Autowired
private IMyDS myDS; 

// then I try to call a function of IMyDS, and get an error at this line :

protected ActionForward executeAction(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws ReefPresentationException {
    myDS.callFunction(form);
}

But it doesn't work, giving me a NullPointerException. So far I've guessed the bean is not correctly injected, so I tried to add some information in my application-context-spring.xml file :

<bean id="myDS" class="com.my.project.service.IMyDS" />

And I get this error :

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'myDS' defined in ServletContext resource [/WEB-INF/config/application-context-spring.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.my.project.service.IMyDS]: Specified class is an interface

So I tried instead to declare the class :

<bean id="myDS" class="com.my.project.service.internal.MyDS" />

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'myDS' defined in ServletContext resource [/WEB-INF/config/application-context-spring.xml]: Instantiation of bean failed; nested exception is java.lang.ExceptionInInitializerError

So I really have no idea of what is wrong right now...

Thanks for your help

Upvotes: 0

Views: 1512

Answers (1)

Kevin Wittek
Kevin Wittek

Reputation: 1572

The errors says it all. You have defined your interface IMyDS as a bean and Spring can't instantiate the interface.

Upvotes: 1

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