'Bean does not have a public constructor that does not take parameters' error despite clearly having one?

Question

I have an EmailService EJB that has a very simple \'send_email\' method. I\'m receving the error in the title despite clearly having a public constructor that does not take para

Answer 1

Just in case you are arriving here several years late as I did, it also turns out this error message may be misleading. I got the error,

[ERROR   ] CNTR4006E: The EVENT_MANAGER_BEAN enterprise bean in the MySpecialEJB.jar module of the some-ear-DEVELOPMENT-SNAPSHOT application failed to start. Exception: com.ibm.ejs.container.EJBConfigurationException: EJB class com.notarealcompany.event.EventManagerEJB must have a public constructor that takes no parameters : some-ear-DEVELOPMENT-SNAPSHOT#MySpecialEJB.jar#EVENT_MANAGER_BEAN
    at com.ibm.ws.ejbcontainer.jitdeploy.EJBUtils.validateEjbClass(EJBUtils.java:346)
    at [internal classes]
Caused by: java.lang.NoClassDefFoundError: commonj/work/Work
    at java.lang.Class.getDeclaredConstructors0(Native Method)
    at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671)
    at java.lang.Class.getConstructor0(Class.java:3075)
    at java.lang.Class.getConstructor(Class.java:1825)
    at com.ibm.ws.ejbcontainer.jitdeploy.EJBUtils.validateEjbClass(EJBUtils.java:337)
    ... 1 more

I don't think the error message is trying to say that such a method does not exist. Rather it's saying that the loader couldn't find one that does exist that can be successfully loaded. The actual error (caused by) is the NoClassDefFoundError on the class commonj.work.Work. It turns out that there is also a warning earlier in the log:

[WARNING ] CWNEN0047W: Resource annotations on the fields of the com.notarealcompany.app.ApplicationEJB class will be ignored. The annotations could not be obtained because of the exception : java.lang.NoClassDefFoundError: Lcommonj/work/WorkManager;

So the Application EJB didn't get its resources injected either because commonj.work.WorkManager could not be found. Why that's a warning and not an error is a good question. I'm sure the app will do just fine without those resources, right? Basically, the jar with the APIs for commonj.work just didn't get included with the deployment. In our case, that's because the old application server provided it whereas the new application server did not. A little adjustment to the POM file and we got past that issue. Very misleading error message in my opinion.