I got two classes with the same package in different JARs. Until the previous version, both classes were identical, so i had no issues in loading them. Now, one of them has a new method added and if I want to access it, not only should I import the class with that package, i also need to make sure the jar with the correct class comes first in the classpath.
i.e. javac -classpath "%classpath%;a.jar;b.jar" MyClasses..
where a.jar has the class with my new method.
Now, how do i ensure this when my app goes to production, where it's deployed as an EAR file, with all the libraries under WEB-INF/lib?
How do I know which jar gets the preference over the other? Is it the alphabetical order like a.jar is given the first preference over b.jar?
I've read this safe-class-imports-from-jar-files thread and got to know about writing a custom classloader, but is there a better simpler solution that? Cos I'm just going to access this method in that whole JAR in this current project and writing a classloader seems a bit overkill.
And please don't ask me "Why the hell same class with same package in different JARs?" It's absolutely out of my control and it'll take some time to get this corrected.
Environment details: IBM WAS 6.1 on their 1.5 Java.
Please ask me more questions, if I don't make much sense. Thanks in advance!
Websphere allows you to specify the order in which classloaders of a particular application are inquired when searching for a class (the classloaders are hierarchically structured, from the topmost that loads JRE classes, down to classloader loading classes in your WAR).
During deployment of an app, you can specify if the order of inquiring the classloaders when searching for a class. There are two modes - Parent first (i.e. query the topmost classloader first) and parent last (query the app classloader first). This can be specified on both EAR and WAR level.
Packaging the duplicated jars to different locations in the app (e.g. one to EAR's classpath, the other to WAR's WEB-INF/lib) and setting the classloader orderING apropriately may solve your problem. However, if both your JARs have to be on the same level (e.g. WEB-INF/lib), then there's no way to specify which one will be used when loading the duplicated class.