Xbooting a Java class [duplicate]

Question

Basically I want to replace the Canvas class at runtime by an application that uses my custom Canvas class, I heard xbooting can do this but there are no tutorials or anything.

So I'm just wondering what the vm arguments are, can you help me please?

Flatus

"uses my custom Canvas class" DYM a java.awt.Canvas? Time to join us in the 3rd millennium & use Swing. BTW 1) What is the use-case here for a) Extending this class. b) Using it instead of the inbuilt class? 2) It will not be legal to distribute this app. AFAIU. – Dulcle

@AndrewThompson - My understanding is that it would not be legal to distribute a JVM that had the custom class instead of the standard one. However, distributing the class together instructions on how to modify the bootclasspath would be OK. (Doesn't make it a good idea though ...) – Bolus

@StephenC Thanks for clarifying. Your suggestion makes more sense. – Dulcle

BTW -1 for ignoring my questions. They were intended to help you arrive at the best solution. – Dulcle

@AndrewThompson I think that Francis should have answered your questions although I do not think they are relevant to the original problem and thus the downvote is not deserved. The problem is simple - how to setup a bootclasspath, that does not need to be justified by a usecase. Plus, as StephenC already pointed out, its perfectly legal to write/distribute such apps. Thank you. – Albion

Answer 1

By xboooting you probably mean the -Xbootclasspath parameter?

You can use the -Xbootclasspath to override the classes that are being loaded when the VM is booting. This way you can give the VM your own implementation of a certain class and it will be used right from the start of the VM. You can do something like this:

java -Xbootclasspath/p:path_to_the_jar_with_myCanvas_class.jar HelloWorld.class

But the -Xbootclasspath won't replace the Canvas class at runtime, the replacement will occur already at the start of the VM.

Here is a nice post about Xbootclasspath : When to use -Xbootclasspath on HotSpot?

Carlocarload

Yea thats what i want haha :) just trying to figure out the rest of the parameters – Flatus