Question

I am working on application which contains few sub modules. On one of these modules I have service with header like this:

@Transactional
@Service("mySimpleService")
public class MySimpleServiceImpl implements MySimpleService {}

On the another module I have a controller in which I would like to use one of the MySimpleService method. So I have something similar to this:

@Controller
public class EasyController {    

    @Autowired
    private MySimpleService mySimpleService;

    @RequestMapping("/webpage.htm")
    public ModelAndView webpage(@RequestParam,
                                @RequestParam,
                                HttpServletRequest request,
                                HttpServletResponse response) {
        ModelAndView mav = new ModelAndView(”webpage”);
        mav.addObject(”name”, mySimpleService.getObject());
        return mav;
    }
}

On the line mav.addObject(”name”, mySimpleService.getObject()); I am getting NullPointerException. I don’t know why. I am not getting error similar to Could not autowire field but only NullPointerException.

I have also created my own interceptor in this way to check some another ideas in my task:

public class CustomInterceptor extends HandlerInterceptorAdapter {

    @Autowired
    private MySimpleService mySimpleService;

    @Override
    public boolean preHandle(HttpServletRequest request, 
                             HttpServletResponse response,
                             Object handler)
                             throws Exception {         
        request.setAttribute("attr", mySimpleService.getAttribute());
        return true;
    }    
}

This interceptor is of course declared in dispatcher servlet. In my logs I can see NullPointerException at line: request.setAttribute("attr", mySimpleService.getAttribute());. So this is exactly problem with getting access to service from another application module.

How can I achieve this?

I have heard about ideas like building EJB with my service and share it using JNDI or using Maven – copy folder with my service to target module during building application. I have tried to do the second option but it isn’t working and I can’t check if the coping was successful. Is possible to check Maven based solution? Do you have another suggestions?

EDIT

This is component scaning from target module dispatcher servlet:

<context:component-scan base-package="my.package.target.module.controller" annotation-config="false"/>

Answer 1

I think your problem is the annotation-config=”false”. The annotation-config feature is what turns on the @Autowired annotation. Without auto-wiring, your mySimpleService properties do not get injected and remain null. Then you get the NullPointerException.

Try

<context:component-scan base-package="my.package.target.module.controller" annotation-config="true"/>

BTW – I have never used this exact configuration, since I don’t do scanning. I always use the separate element:

<context:annotation-config />