java之反射进阶

我们反射通常使用第一种方式,首先来看看Class.forName(clssName): 注意：传入的className必须是类的全路径,否则会报错java.lang.ClassNotFoundException。

public static Class forName(String className)
                throws ClassNotFoundException {
        return forName0(className, true, ClassLoader.getCallerClassLoader());
    }

通过调用forName0方法，使用ClassLoader.getCallerClassLoader()来加载ClassLoader

    // Returns the invoker's class loader, or null if none.
    // NOTE: This must always be invoked when there is exactly one intervening
    // frame from the core libraries on the stack between this method's
    // invocation and the desired invoker.
    static ClassLoader getCallerClassLoader() {
        // NOTE use of more generic Reflection.getCallerClass()
        Class caller = Reflection.getCallerClass(3);
        // This can be null if the VM is requesting it
        if (caller == null) {
            return null;
        }
        // Circumvent security check since this is package-private
        return caller.getClassLoader0();
    }

在获取ClassLoader调用claser.getClassLoader0() 这是一个私有包，可以避免安全检查。

 // Package-private to allow ClassLoader access
    native ClassLoader getClassLoader0();

1、ClassLoader到底是个什么东西