java之反射进阶

2019-11-08 00:42:44

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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();