reflection and overloading, java.lang.IllegalArgumentException: wrong number of arguments

[Alessandro Ilardo]

I am testing an ejb with a client which uses the Junit framework.
On the ejb I have two public methods

public User getUser(final String email, final String domain)
public User getUser(final Long id)

the client code is something like this

 
public Object invokeRemoteMethod(String keyName, Object[] params) throws ServiceLocatorException {
        Object result = null;
        try {
            if (this.ejbObj == null) {
                this.setEjbObj();
            }
            logger.debug("[invokeRemoteMethod] Got EJB object.");
            Method mth = this.getRemoteMethod(keyName, params);
//            Method mth = this.getRemoteMethod(this.getEjbProp(keyName), params);
            logger.debug("[invokeRemoteMethod] Got EJB method.");
            if (mth.getReturnType() != null) {
                result = mth.invoke(this.ejbObj, params);
            } else {
                mth.invoke(this.ejbObj, params);
            }
            logger.debug("[invokeRemoteMethod] EJB method invoked.");
        } catch(InvocationTargetException ex) {
            logger.fatal(ex.getCause());
            throw new ServiceLocatorException(ex.getMessage());
        } catch (Exception ex) {
            logger.fatal(ex);
            throw new ServiceLocatorException(ex.getMessage());
        }
        return result;
    }


private Method getRemoteMethod(String keyName, Object[] params) throws ServiceLocatorException {
        Method mth = methodsCache.get(getEjbProp(keyName));
        if (mth == null) {
            try {
                if (ejbClass == null) {
                    this.setEjbClass();
                }
                Class[] clazzes = new Class[params.length];
                for (int i = 0; i < params.length; i++) {
                    clazzes[i] = params[i].getClass();
                }
                mth = ejbClass.getMethod(keyName, clazzes);
            } catch (Exception ex) {
                logger.fatal(ex);
                throw new ServiceLocatorException(ex.getMessage());
            }
            methodsCache.put(getEjbProp(keyName), mth);
        }
        logger.info("[getRemoteMethod] EJB method succesfully found.");
        return mth;
    }
 

called by a junit test

 
@Test(expected=NoResultException.class)
    public void testGetUser(){
        remMthParam = new Object[]{getMockUsr().getUsername(),
                    getMockUsr().getDomain()
                };
        logger.debug("[testGetUser] Start test.");
        try {
            returnedObj = getServiceInterf().invokeRemoteMethod("getUser", remMthParam);
        } catch (ServiceLocatorException ex) {
            logger.fatal("[testGetUser] " + ex.getMessage());
        }
    }

The test doesn't complete correctly and I get this exception
834 [main] FATAL eu.virtualLab.security.user.test.util.ServiceLocator - java.lang.IllegalArgumentException: wrong number of arguments
835 [main] FATAL eu.virtualLab.security.user.test.junit.JunitUserActions - [testGetUser] wrong number of arguments

Could you please give me some help about it?
Thanks in advance

[Campbell Ritchie]

Don't know, sorry, but that looks too difficult for us beginners. Moving.

[Steve Luke]

It looks to me like you have to find a better way of caching methods. You have 2 methods with different numbers of parameters. Whichever is the first one that is searched for will be cached and returned for any time another method with the same method name is called. This will cause problems when you would have overloaded methods with different single parameters as well (for example a getUser(Long) and a getUser(Integer)).

I would suggest putting more information in the cache's key, for example the method name and the list of parameter types. For example this would be a utility method that could help you generate a more useful key:

    static String generateMethodKey(String methodName, Object[] params)
    {
        StringBuilder output = new StringBuilder(methodName);
        output.append("(");
        for (Object obj : params)
        {
            output.append(obj.getClass().getName()).append(",");
        }
        output.setCharAt(output.length() - 1, ')');

        return output.toString();
    }

You could call it in your getRemoteMethod() method like:

private Method getRemoteMethod(String keyName, Object[] params) throws ServiceLocatorException {
        String methodKey = generateMethodKey(keyName, params);
        Method mth = methodsCache.get(methodKey); //or whatever ejbProp does...
        if (mth == null) {

            ...

            methodsCache.put(methodKey, mth);
        }
        logger.info("[getRemoteMethod] EJB method succesfully found.");
        return mth;
    }

[Alessandro Ilardo]

Thank you, you're right