Frequently Asked Questions

This page will eventually become the HiveMind FAQ. The idea is that people ask questions and that other HiveMind users and developers respond and comment until a "accepted solution" is reached. Eventually we will be able to compile a list of questions and accepted solutions into a more official FAQ for the HiveMind website.

Question 1): InjectingNonServiceFactoryObtainedObjects (DanielFeist 21/06/2004)

Is there anyway to inject a service, using the BuilderFactory, with an object obtained by invoking a method of another service thus allowing non-service objects to be obtained from a POJOF (plain old java object factory) for injection?

Question 2): UsingJNDIToObtainHiveMindServices (DanielFeist 24/06/2004)

I have been experimenting with the use of JNDI as a facade to HiveMind by implementing a simple JNDI SPI. The lookup method of a JNDI Context takes just a Name, yet to obtain a HiveMind service i need to be able to specifiy the interface expected. What i have found is that i can, in place of the interface expected put Object.class and everything works ok. Object is not an interface so i'm not quite sure why this works. Is this intentional? Will HiveMind continue to support this?

Accepted Answer:

HowardLewisShip: Yes, passing Object.class will continue work but it is not recommended in normal cirmcumstaces. The idea of passing in the expected (assignable) type is to allow HiveMind to do a check that the service object or proxy returned is assignable. Better a good message from inside HiveMind than a bad ClassCastException. Using java.lang.Object is acceptible if you don't care about that test.

Question 3): PuttingHivemindConfigurationFilesOutsideAnEAROrWAR (TomDavies 24/09/2004)

I have configuration data which may change reasonably often, and which I'd like an administrator to be able to change without rebuilding an ear/war file. What's the best way to make this available to HiveMind?

Answer

Michael Frericks: You could add files that reside outside the classpath as modules this way:

ClassResolver resolver = new DefaultClassResolver();
RegistryBuilder builder = new RegistryBuilder();

// process classpath modules
builder.processModules(resolver);


// process modules located anywhere else
File[] modules = getHiveModules(confPaths);

for (int i = 0; i < modules.length; i++)
{
    File module = modules[i];
    builder.processModule(resolver,
	new URLResource(module.toURL()));
}

Registry registry = builder.constructRegistry(Locale.getDefault());

Question 4): How can I use HiveMind to lookup my EJB remote component interfaces? (aka ServiceLocator pattern) (DavidKarlsen 03/10/2004)

I'd like to lookup my EJB beans and receive the narrowed remote component interface via HiveMind.

Answer

David Karlsen: Use the hivemind.lib.EJBProxyFactory:

<module id="com.mypackage" version="1.0.0">
         <service-point id="SessionFacade" interface="com.mypackage.SessionFacade">
         <invoke-factory service-id="hivemind.lib.EJBProxyFactory">
                 <construct
                 home-interface="com.mypackage.SessionFacadeHome"
                 jndi-name="ejb/com/mypackage/SessionFacadeHome"/>
         </invoke-factory>
         </service-point>
</module>

Then in your code:
//initialize Registry registry some way
SessionFacade sf = (SessionFacade) registry.getService(SessionFacade.class);

Question 5): How does one explicitly enable logging within Hivemind? (mferris 03/29/2004)

When I run, I get the spew below, which I see comes from the guts of the RegistryBuilder. I specify an interceptor class, but the problem is that Hivemind is not instantiating my service, hence I get no interception. Another service point in the same hivemodule.xml DOES get instantiated. I get a runtime error of:
Unable to construct service tradeworkflow.TradeLifecycleService: Failure invoking constructor for class trade.workflow.service.TradeLifecycleService (at META-INF/hivemodule.xml, line 9, column 86)

The hivemodule line and column referenced contains the > symbol (the end of the <construct class line)

L O G G I N G C O N F I G U R A T I O N E R R O R

Logging is not enabled for org.apache.hivemind.impl.RegistryBuilder.
Errors during HiveMind module descriptor parsing and validation may not be
logged. This may result in difficult-to-trace runtime exceptions, if there
are errors in any of your module descriptors. You should enable error
logging for the org.apache.hivemind and hivemind loggers.

I attempted to pass in -Dorg.apache.commons.logging.Log=org.apache.commons.logging.impl.Jdk14Logger -Dorg.apache.hivemind=SEVERE at the command line, but this has no effect.

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