如何修改第三方代码

Question

A supposedly simple architectural/design question:

Our Java application is depending on a third party code. However, this third party code does a little thing that I don't like (set's the timeZone to GMT; I'd like to set the timezone differently based on TimeZoneID of the application). What are my options?

1- I can't simply extend the third party classes and override the undesired behavior, since there are callers to the 3rd party classes from litterally everywhere in our application (this is the way that we inherited the application to begin with).

2- Maybe the too invasive solution is to write our own equivalent of the third party code and depend on that instead. But, that's too much and too invasive probably.

3- I looked at Spring AOP (and aspectJ) stuff a little bit to do load time weaving. I didn't dive in it too much, but it seemed to me that since the third party code calls java.util.Timezone.setDefault(GMTTimeZone); (as opposed to calling a class that we wrote/manage ourselves) It can't be done that easily. I could be wrong here, and maybe I can still weave around java.util.Timezone.setDefault(). Please let me know if this is ture, and it is pretty much my (only) solution.

4- Am I missing something, or that's pretty much all available options?

Answer 1

First, you could contact the third party and ask them to change the code. It's not as long of a shot as you might think. It annoys you, and probably their other customers.

Also, you could use a subclass as a proxy into your code only. Others on your project don't have to use your subclass, necessarily. You could clean up the undesired behavior and abstract the change out of your code. You could also send this code to the vendor when asking them to change the behavior!

Lastly, the easiest solution would be to just take the return value and fix it in-line. It's the fastest way to get it done now, but it's not a good pattern to follow, as you're introducing code that's only used to fix other people's problems.

Answer 2

You're probably pretty much limited to what you've posted. As smcg said, it might be best to fork the code (if possible) and simple change the code then recompile it. On the AOP, if you could monkey patch the code then you could replace the method that calls the setDefault() on the timezone.

Answer 3

extend that class from your class and override that method (fill code according to your requirement) in your subclass, but that class and method should not be declared as final in that third party code.

ThirdPartyClassName obj=new YourSubClassName();

    obj.yourOverridenMethod()

This will call your overridden method of your sub class and all other calls will call the original method of third party class