在不必改变原类文件和使用继承的情况下，动态地扩展一个对象的功能。它是通过创建一个包装对象，也就是装饰来包裹真实的对象。-When there is no change of the original class files and the use of inheritance, and dynamic expansion of an object function. It is by creating a wrapper object, object is to wrap the real decoration.