Question

I Have a code:

public class testCustomer {

    private ModelMap customer;
    }

And getters/setters for above class.

And I have two methods:

@ActionMapping(params = "action=search")
    public void searchAction(
            ActionRequest request,
            ActionResponse response) {

            ModelMap modelMap = new ModelMap();
            modelMap.put("rowsPerPage", 10);
            modelMap.put("page", 1);
            modelMap.put("total", 100);

            testCustomer.setCustomer(modelMap);
    }


@ResourceMapping(value="customer")
    public ModelAndView listCustomer(
            ResourceRequest req,
            ResourceResponse res) {


        ModelAndView mav = new ModelAndView();
        MappingJacksonJsonView v = new MappingJacksonJsonView();

        mav.setView(v);
        if(testCustomer.getCustomer().isEmpty()){
            log.debug("List Customer Resource: " + "NULL");
            mav.addObject("data", null);
        } else {
            log.debug("List Customer Resource: " + testCustomer.getCustomer());         
            mav.addObject("dataListCustomer", testCustomer.getCustomer());
        }
        return mav;
    }

How Can I check in @ResourceMapping if testCustomer is empty or not? Because now I have NullPointer Exeption
What is wrong in my code?

Answer 1

In java, null is different to “being empty”. Calling any method on a null will result in a NullPointerException. You must explicitly test for null before calling isEmpty().

Change your code to this:

if (testCustomer.getCustomer() == null || testCustomer.getCustomer().isEmpty())