Java ClassLoader委托模型？

正确的类加载器实现将：

1. 检查该类是否已经加载。
2. 通常要求父类加载器加载该类
3. 尝试在自己的班级路径中查找班级。

ClassLoader.loadClass的默认实现是这样的：

protected synchronized Class<?> loadClass(String name, boolean resolve) {  // First, check if this class loader has directly defined the class or if the  // JVM has initiated the class load with this class loader.  Class<?> result = findLoadedClass(name);  if (result == null) {    try {      // Next, delegate to the parent.      result = getParent().loadClass(name);    } catch (ClassNotFoundException ex) {      // Finally, search locally if the parent could not find the class.      result = findClass(ex);    }  }  // As a remnant of J2SE 1.0.2, link the class if a subclass of the class  // loader class requested it (the JVM never calls the method,  // loadClass(String) passes false, and the protected access modifier prevents  // callers from passing true).  if (resolve) {    resolveClass(result);  }  return result;}

一些类加载器实现将委派给其他非父类加载器（例如，OSGi，取决于包，委派给类加载器的图），而某些类加载器实现会在委派之前在本地类路径中查找类。