Imagine I have a bunch of classes, that can do logging, so I've created a logger interface and a couple of implementations (writing to file, to stdout, to db, etc.), but sometimes I don't care about logging those messages, so I've made an implementation, that simply ignores all of the messages.Imagine I have a bunch of classes, that can do
阅读背景：
构造函数注入——如果构造函数中没有提供新的null对象，是否可以使用它?
来源：互联网
分享到：
