Questions on Java Reflection in EJB

Question

Hi,
Recently, I use reflection technology on EJB to get/set properties of a bean.
We need it because we need to encapsulate data in a map to transfer data between
presentation layer and business back end(i.e. the so-called value data object).
A bean is packed into a map as following:
The property name of a bean becomes the key in the map, and its value becomes the
corresponding value in the map.
So we have to do two things:
1)Given a bean, convert it to a map;
2)Given a data map, assign the value to a bean
It would be nice if we can implement the two requirements in a base class. So I use
reflection. And succeed to achieve the goal.
But there are two problems occured and I can't understand why.
1)If I use Class.forName() to load the entity bean implementation class(BMP or CMP abstract
schema) I got a ClassNotFoundException. A workaround is to jar the BMP or CMP bean class
and place it on the classpath.
So, I want to know why there is such restriction.
2)For the classes java.lang.reflect.Method, java.lang.reflect.InvocationTargetException
I reference to in bean class, the IDE(I use IntelliJ Idea) give me a
warning: "Use java.lang.reflect.Method are not allowed in EJB". Are the methods really
dangerous in EJB environment?
Can anyone explain me these pluzzles?
Thank you in advance!
BTW, I develop under weblogic 7.0. Now, my program functions well, I just can't understand
the above phenomena.
Regards,
Justine

Answer 1

1) You should never directly manipulate the EJB implementation class. That class is for the container. When accessing EJBs (no matter the means), you should use the Home/Remote or Local interfaces - those your client should already have. If what you're doing is actually working for you, I can only say that you're not using EJBs properly and are not getting the actual "bang for the buck" you paid for. And you're damn lucky it hasn't blown bits all over the place...
2) Yes, it is potentially dangerous to be dorking around with reflection on EJBs. When you're using the Home/Remote or Local interfaces, you're actually using an Object that the vendor supplies to perform the actual remote operations. Using reflection could potentially invoke one of the "hidden" vendor methods with extremely unpredictable results - like deleting your entire table.
As for using a map for transferring data, I would strongly recommend against it, especially in this case, because you've not only lost the strong typing you get with ValueObjects, but you have to do a lot of extra work on both "sides" (client and EJB) to make sure all your data is present and/or correct.