Java - Load a class outside of classpath. What are the options

问题

I got a Java product which is used by many clients. The product gets added as a jar into the client's (say for example XYZ company who wants to use his product for their needs) code base and works independently. Its a stand alone product and all the client projects depends (maven dependency) on this one product (which again is a couple of java projects bundled as a jar rolled out with a license)

Now i am in a situation to make the engine use a class outside of it's class path. It's a client class and I don't want to move that class into the products code base and keep it outside but still want to use it.

Just to confirm I tested it and its saying that class not found as expected. One option i can think of is jar those specific classes and add it to my product's classpath

Is their any other better ideas?

回答1:

I think you have three options (EDIT -- more details):

1. load a class from a File on the filesystem, using a URLClassLoader:

   see this answer;

2. create the class using reflection:

   you still need the class to be in classpath, or you need to load it through filesystem (option 1), see this.

3. middle way solution: you can add an interface to your standalone product, and then create your implementing class with reflection; I never did this in production, I just tested the code and it works: see this question

来源：https://stackoverflow.com/questions/24286379/java-load-a-class-outside-of-classpath-what-are-the-options