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anasustic
Level 6
June 24, 2022
Solved

How to use #onChange in ResourceChangeListener

  • June 24, 2022
  • 2 replies
  • 1200 views

Hi

I would like to know if and why do I need the NotNull Constraint when implementing onChange in ResourceChangeListener. Here is the code:

 

public class ComponentCampaignCleanupListener implements ResourceChangeListener {

    private static final Logger logger = LoggerFactory.getLogger(ComponentCampaignCleanupListener.class);

    @Reference
    private ResourceResolverService resourceResolverService;


    @Override
    public void onChange(List<ResourceChange> list) {...} //**Do I need here @NotNull  for the list parameter and why?
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Best answer by aanchal-sikka

I have tried both ways. It is working fine for me

@9944223 public void onChange(List<ResourceChange> changes) { logger.info("On Change Event !!!"); changes.forEach(change -> { logger.info("Resource event: {} at: {}", change.getType(), change.getPath()); }); } @9944223 public void onChange(@NotNull List<ResourceChange> changes) { logger.info("On Change Event !!!"); changes.forEach(change -> { logger.info("Resource event: {} at: {}", change.getType(), change.getPath()); }); }

 

 

2 replies

T
Adobe Employee
Tushar_GuptaAdobe Employee
Adobe Employee
June 24, 2022

I dont think it is mandatory to define notnull here. Refer below 

https://github.com/apache/sling-org-apache-sling-discovery-commons/blob/4f7d7ca3224239d52798cc8418ec8283f5eddc9e/src/main/java/org/apache/sling/discovery/commons/providers/spi/base/IdMapService.java 

 

The @126844 Annotation is, actually, an explicit contract declaring the following:

  1. A method should not return null.
  2. A variable (like fields, local variables, and parameters) cannot should not hold null value.

Additionally, @126844 is often checked by ConstraintValidators (eg. in spring and hibernate).

The @126844 annotation doesn't do any validation on its own because the annotation definition does not provide any ConstraintValidator type reference.

    A
    anasusticAuthor
    Level 6
    June 24, 2022

    Thanks @tushar_gupta 

    In my specific case the list variable could be null. I am listening to /content ADDED changes. In fact, if I add the @NotNull constraint AEM I cannot render any Page and get a compilation error.

    The reason why I posted the question is that I thought according to the interface, this method should have a @NotNull annotation.

     

    Here is the interface:

    @ConsumerType
    public interface ResourceChangeListener {
        String PATHS = "resource.paths";
        String CHANGES = "resource.change.types";
        String PROPERTY_NAMES_HINT = "resource.property.names.hint";

        void onChange(@NotNull List<ResourceChange> var1);
    }

    I 

      aanchal-sikka
      Community Advisor
      aanchal-sikkaCommunity AdvisorAccepted solution
      Community Advisor
      January 31, 2024

      I have tried both ways. It is working fine for me

      @9944223 public void onChange(List<ResourceChange> changes) { logger.info("On Change Event !!!"); changes.forEach(change -> { logger.info("Resource event: {} at: {}", change.getType(), change.getPath()); }); } @9944223 public void onChange(@NotNull List<ResourceChange> changes) { logger.info("On Change Event !!!"); changes.forEach(change -> { logger.info("Resource event: {} at: {}", change.getType(), change.getPath()); }); }

       

       

      Aanchal Sikka
        SantoshSai
        Community Advisor
        SantoshSaiCommunity Advisor
        Community Advisor
        June 24, 2022

        Hi @anasustic ,

        If you want to use Javax validation constraints to ensure that the List<ResourceChange> list

         being passed in is not null then @NotNull annotation is being used.

        Fore more details please visit: https://docs.oracle.com/javaee/7/api/javax/validation/constraints/NotNull.html

        Hope that helps!

        Regards,

        Santosh

        Santosh Sai
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