Difficult ClassLoader problems with multiple deployed enterprise Apps

Greetings!

When multiple instances of an enterprise application are deployed, ClassLoader issues are causing ClassCast Exceptions in the instantiation of Stateless SessionBeans. These ClassCast Exceptions are causing the Stateless Session beans to not be created appropriately/correctly, and in turn there is an InvocationTargetException resulting in an HTTP 500 Internal Server Error (mapped to a custom handler).

The setup is SJSAS2005Q2, JDK 1.5, MySQL 5.0, Linux (RedHat 9, and Debian 3.0/3.1)

Below is a typical example:

Exception creating stateless session bean : [{0}]java.lang.reflect.InvocationTargetException

<<long stack Trace omitted>>

Caused by: java.lang.ClassCastException: $Proxy111at com.acjust.ecommerce.ejb.preferences.PreferenceManagerBean.ejbCreate(PreferenceManagerBean.java:354)... 67 more

Here is the code from PreferenceManagerBean, the offending line is the (first one) that does a lookup on PreferencesBean and casts the result. This is a SessionFacade (there are many others) and they all (may) exhibit this behavior when there are multiple enterprise apps running.

publicvoid ejbCreate(){

LookupServiceHelper lookup = LookupServiceHelper.getInstance();

preferencesHome = (LocalPreferencesHome)

lookup.getLocalHome(IConstants.PREFERENCES_BEAN);

companyInformationHome = (LocalCompanyInformationHome)

lookup.getLocalHome(IConstants.COMPANY_INFORMATION_BEAN);

businessAddressHome = (LocalBusinessAddressHome)

lookup.getLocalHome(IConstants.BUSINESS_ADDRESS_BEAN);

sitePreferencesHome = (LocalSitePreferencesHome)

lookup.getLocalHome(IConstants.SITE_PREFERENCES_BEAN);

paymentPreferencesHome = (LocalPaymentPreferencesHome)

lookup.getLocalHome(IConstants.PAYMENT_PREFERENCES_BEAN);

productPreferencesHome = (LocalProductPreferencesHome)

lookup.getLocalHome(IConstants.PRODUCT_PREFERENCES_BEAN);

}

When there is one instance of the App, it works perfectly. When there are two instances, one works perfectly, and the other one will have the above issues with the instantiation of Stateless Session Beans (the broken enterprise app is the one that is NOT loaded or reloaded most recently).

Thinking that the problem may be solved by rearranging or repackaging the software, multiple solutions have been tried. (ClassCast Exceptions such as these are typically the result of helper classes being loaded by one class-loader, then loaded by another, compared or casted, and the two are not equivalent). In this case, though, the software is behaving as though each enterprise app does not have its own class loader hierarchy, which is obviously highly undesirable for the situation at-hand. At any rate, bundling all library classes at the app server classpath level, putting all library classes in each jar, and war, and putting all library classes in the ear/lib directory and using MANIFEST.MF classpath entries to point all ear subcomponents at the library classes - none of these potential solutions has alleviated this problem. In addition, the EJB classes themselves triggering the exception(s) are not helper classes but EJBs that are correctly packaged in their respective EJB-JARS.

Here is the sun SJSAS 8 classloader hierarchy from the userguide:

http://docs.sun.com/source/817-6087/dgdeploy.html#wp58491

Can somebody from the Sun App Server team speak to whether or not this is an Application Server issue? Why should the classloader hierarchy from one enterprise app interfere with any other? Are there known workarounds?

Any help is greatly appreciated.

Best, Adam

[3898 byte] By [adamjusta] at [2007-10-2 4:47:38]

Java programming resources: FAQs, tutorials, compiler and browser download sites, documentation, books lists, IDEs, etc.

Difficult ClassLoader problems with multiple deployed enterprise Apps

Enterprise & Remote Computing New Topic

Enterprise & Remote Computing Hot Topic

Enterprise & Remote Computing

All Classified