Java：Class.forName和ClassLoader.loadClass之间的区别 [英] Java: Difference between Class.forName and ClassLoader.loadClass

问题描述

最近遇到一些让我思考的代码。有什么区别：

Recently came across some code that got me thinking. What's the difference between:

Class theClass = Class.forName("SomeImpl");
SomeImpl impl = (SomeImpl)theClass.newInstance();

和：

Class theClass = ClassLoader.loadClass("SomeImpl");
SomeImpl impl = (SomeImpl)theClass.newInstance();

它们是同义词吗？在某些情况下，是否优先于另一方？使用这两种方法有什么用，有什么用呢？

Are they synonymous? Is one preferable to the other in certain circumstances? What are the do's and dont's to using these two methods?

提前致谢。

推荐答案

Class.forName（）将始终使用调用者的ClassLoader，而ClassLoader.loadClass（）可以指定不同的ClassLoader。我相信Class.forName也会初始化加载的类，而ClassLoader.loadClass（）方法不会立即执行（它在第一次使用之前不会初始化）。

Class.forName() will always use the ClassLoader of the caller, whereas ClassLoader.loadClass() can specify a different ClassLoader. I believe that Class.forName initializes the loaded class as well, whereas the ClassLoader.loadClass() approach doesn't do that right away (it's not initialized until it's used for the first time).

在查看确认初始化行为的摘要时刚刚发现了这篇文章。看起来这里有您正在寻找的大部分信息：

Just found this article when looking to confirm my summary of the initialization behavior. It looks like this has most of the information you're looking for:

http://www.javaworld.com/javaworld/javaqa/2003-03/01-qa-0314-forname.html

这个用法很酷，虽然我之前从未使用过它：

This usage is pretty cool, though I've never used it before:

Class.forName(String, boolean, ClassLoader)

它允许您指定ClassLoader并且boolean参数定义是否应该在加载类时初始化类。

It allows you to specify a ClassLoader and the boolean parameter defines whether the class should be initialized when it's loaded or not.

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