定义自定义系统类加载器 [英] Define custom system classloader

问题描述

我试图告诉JVM将自定义的ClassLoader用作默认的ClassLoader

I'm trying to tell the JVM to use my custom ClassLoader as default ClassLoader

这是我用来选择类的VM参数：

This is the VM argument i use to pick my class:

-Djava.system.class.loader=JarClassLoader

这是我得到的错误

Error occurred during initialization of VM
java.lang.Error: java.lang.NoSuchMethodException: JarClassLoader.<init>(java.lang.ClassLoader)
    at java.lang.ClassLoader.initSystemClassLoader(Unknown Source)
    at java.lang.ClassLoader.getSystemClassLoader(Unknown Source)
Caused by: java.lang.NoSuchMethodException: JarClassLoader.<init>(java.lang.ClassLoader)
    at java.lang.Class.getConstructor0(Unknown Source)
    at java.lang.Class.getDeclaredConstructor(Unknown Source)
    at java.lang.SystemClassLoaderAction.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.lang.ClassLoader.initSystemClassLoader(Unknown Source)
    at java.lang.ClassLoader.getSystemClassLoader(Unknown Source)

我必须定义特定的方法还是使用错误的参数？

Do i have to define a specific method or am i using the wrong argument?

推荐答案

自定义ClassLoader

Custom ClassLoader

public class CustomClassLoader extends ClassLoader{

    public CustomClassLoader(ClassLoader classLoader) {
        super(classLoader);
    }

    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException {
        System.out.println("Loading class :" + name);
        return super.loadClass(name);
    }
}

主班

public class Main {

    public static void main(String[] args) {
        System.out.println("Starting main");
    }
}

VM参数： -Djava .system.class.loader = CustomClassLoader

所有类都在默认包中，并且可以成功执行。

All classes are in default package and it executes successfully.

输出：

加载类：Main

启动main

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