ClassWriter cw = new ClassWriter(...);
byte[] bytes = cw.toByteArray();
I would like to create new class instance from bytes array. How do I do this? Is it possible at all?
asked Nov 23, 2010 at 17:41
Denys Kniazhev-Support Ukraine
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1possible duplicate of Java: How to load Class stored as byte[] into the JVM?bruno conde– bruno conde2010-11-23 17:44:33 +00:00Commented Nov 23, 2010 at 17:44
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@bruno conde: It looks like. We just express things in a more concise way hereDenys Kniazhev-Support Ukraine– Denys Kniazhev-Support Ukraine2010-11-23 17:54:42 +00:00Commented Nov 23, 2010 at 17:54
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You can use defineClass, however unless you use a custom class loader you may need to use reflections to call it as its not a public method.Peter Lawrey– Peter Lawrey2010-11-23 22:39:50 +00:00Commented Nov 23, 2010 at 22:39
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3 Answers
ClassLoader.defineClass()
Reference:
3 Comments
Sean Patrick Floyd
Nice answer but awful formatting and a java 1.4 link. Changed both.
Vladimir Ivanov
thanks for editing, was struggling with that, but parser didn't want to show the link properly.
Tomas Narros
+1. Anyway, the method is protected, so you'll need a way to access it. Extending the ClassLoader and providing a public method could be a solution.
This is possible, and you need to use Reflection in order to achieve this. The psuedo code is:
final Class clazz = loadIntoCurrentClassLoader(bytes); //I'm assuming you wrote this already using defineClass
final YourClass foo ;
try {
foo = (YourClass) clazz.newInstance();
}
catch (final Exception e) {
throw new RuntimeException(e);
}
4 Comments
Sean Patrick Floyd
I'm pretty sure the
loadIntoCurrentClassLoader(bytes) part is what the question is about :-)
Amir Afghani
Ok so I went a little overboard ;)
Amir Afghani
It's ambiguous from the way the question is phrased.
AlexR
The point is not clazz.newInstance(). The point here was how to get clazz. Reflection does not help here, you should use classLoader.defineClass()
I can create the class by extending ClassLoader and using defineClass. But then the created class has my extended ClassLoader as its ClassLoader, which causes failures when the code of my class loads other classes. Presumably I can get around this by creating my ClassLoader to delegate everything in the right way, but it's not obvious how to get this right.
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