NPE when logging inside a property getter

[cyberanto]

I get a Nullpointer Exception when I add a log statement to my property getter. Example:

---------------------------------------------------
@Name("editDataView")
public class EditDataViewAction ...

skuSelectionAction() {
...
Contexts.getSessionContext().set("skuModel", selectedSku);
...
}

----------------------------------------------------
@Scope(SESSION)
@Name("skuModel")
public class SkuModel ...

@Logger private Log log;

private List features = new ArrayList();

// lazy loading
public List getFeatures() {
if (features.size() < 1) {
log.info("features.size() was smaller than 1");
try {
features.addAll(featureDao.getFeaturesByFeatureListId(featureListId, this));
} catch (ServerException e) {
e.printStackTrace();
}
}
return features;
}

Caused by: java.lang.NullPointerException
at com....model.SkuModel.getFeatures(SkuModel.java:196)
at com....view.EditDataViewAction.skuSelectionAction(EditDataViewAction.java:53)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

If I take out the log statement, this works just fine ... looks like the Logger has not been initialized at reflection time?

Seam version: 2.0.1.CR1

[pmuir]

Where do you call getFeatures from?

[jdijkmeijer]

Also make sure that your Log is a seam Log, and not a commons log or something different. check your import.s

[cyberanto]

hmm, I had transferred a couple of DAOs from another project which had been using commons logging.

After replacing all my commons logging imports with seam.log.Log, all hell is breaking loose ...

e.g.

==========================================

import org.jboss.seam.annotations.Logger;
import org.jboss.seam.log.Log;

@Name("applicationCache")
@Scope(APPLICATION)
public class SwcmApplicationCache implements Serializable {

@Logger private Log log;

CategoryDAO categoryDao = new CategoryDAO();

public String refreshCategories() {
String outcome = ActionOutcomes.SUCCESS;

try {
categories.clear();
categories.addAll(categoryDao.getAllCategories());
staleCategory = false;
} catch (ServerException e) {
e.printStackTrace();
outcome = ActionOutcomes.FAILURE;
}

log.info("updating application cache categories outcome: "+outcome);
return outcome;
}

...
}

============================================

@Name("categoryDao")
public class CategoryDAO extends AbstractDAO {

@Logger private Log log;

public ArrayList getAllCategories() throws ServerException {

...
System.out.println("Logger is: "+log);
log.info("#0 categories returned ...", categories.size());
return categories;
}
}

bombs on Line 55 - the log.info() in the CategoryDAO ... (categories is NOT null) ...

14:39:56,171 INFO [STDOUT] Logger is: null

Caused by: java.lang.NullPointerException
at com.jostens.swcm.sql.CategoryDAO.getAllCategories(CategoryDAO.java:55)
at com.jostens.swcm.application.SwcmApplicationCache.refreshCategories(SwcmApplicationCache.java:68)


Unless someone can tell me what I am doing wrong, I may have to replace all my logging with System.out.print()'s ...


I am using JBOSS Developer Studio and set up my project using its ejb wizard. The SEAM Logger works fine in some other classes ...

[cyberanto]

I found out what my mistake was:

I didn't use injection to create the component which contained the SEAM Logger ...

injecting the component initializes the Logger correctly.

@In(create=true)
private CategoryDAO categoryDao;

//
// CategoryDAO categoryDao = new CategoryDAO();

There used to be a class org.jboss.seam.log.LogImpl ... not any more

How do I get a Seam Logger if I want to instantiate the class "normally" ?

[nickarls]

Haven't used it but Logger seams to have some static methods that might be interesting.