如何检测java系统类？
我正在尝试向系统类（FileInputStream/FileOutputStream）添加自定义行为。我使用以下转换方法编写了自定义 ClassFileTransformer：
public byte[] transform(ClassLoader arg0, String arg1, Class arg2, ProtectionDomain arg3, byte[] arg4) throws IllegalClassFormatException {
System.out.println("class name: " + arg1);
return arg4;
}
当我运行示例程序时：
public static void main(String[] args) throws Exception {
new FileOutputStream("file");
}
我看到没有系统类未传递给转换。
有没有办法修改系统类？提前致谢！
I'm trying to add custom behaviour to system classes (FileInputStream/FileOutputStream). I wrote custom ClassFileTransformer with the following transform method:
public byte[] transform(ClassLoader arg0, String arg1, Class arg2, ProtectionDomain arg3, byte[] arg4) throws IllegalClassFormatException {
System.out.println("class name: " + arg1);
return arg4;
}
When I run sample program:
public static void main(String[] args) throws Exception {
new FileOutputStream("file");
}
I see that no system classes are not passed to transform.
Is there any way to modify system classes? Thanks in advance!
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在调用 pre-main 方法并添加 ClassFileTransformer 之前，一些（不是全部）系统类已经加载。如果您也想转换这些类，则可以在添加 ClassFileTransformer 后调用类似 Instrumentation#retransformClasses(Instrumentation#getAllLoadedClasses()) 的内容。请注意，您必须使用 Instrumentation#addTransformer(ClassFileTransformer, true) 来指示您的转换器支持类的重新转换。
Some (not all) system classes are already loaded before the pre-main method is invoked and your ClassFileTransformer is added. If you want to transform these classes as well, you can invoke something like Instrumentation#retransformClasses(Instrumentation#getAllLoadedClasses()) after adding your ClassFileTransformer. Note, you have to use Instrumentation#addTransformer(ClassFileTransformer, true) to indicate that your transformer supports retransformation of classes.