为什么 Class.newInstance() 是“邪恶的"? [英] Why is Class.newInstance() "evil"?

问题描述

Ryan Delucchi 问此处 评论 #3 到 汤姆霍廷的回答:

Ryan Delucchi asked here in comment #3 to Tom Hawtin's answer:

为什么 Class.newInstance() 是邪恶的"?

why is Class.newInstance() "evil"?

这是对代码示例的回应:

this in response to the code sample:

// Avoid Class.newInstance, for it is evil.
Constructor<? extends Runnable> ctor = runClass.getConstructor();
Runnable doRun = ctor.newInstance();

那么，为什么是邪恶的?

so, why is it Evil?

推荐答案

Java API 文档解释了原因 (http://java.sun.com/javase/6/docs/api/java/lang/Class.html#newInstance()):

The Java API documentation explains why (http://java.sun.com/javase/6/docs/api/java/lang/Class.html#newInstance()):

请注意，此方法会传播空构造函数抛出的任何异常，包括已检查的异常.使用此方法可以有效地绕过编译器否则会执行的编译时异常检查.Constructor.newInstance 方法通过将构造函数抛出的任何异常包装在(已检查的)InvocationTargetException 中来避免此问题.

Note that this method propagates any exception thrown by the nullary constructor, including a checked exception. Use of this method effectively bypasses the compile-time exception checking that would otherwise be performed by the compiler. The Constructor.newInstance method avoids this problem by wrapping any exception thrown by the constructor in a (checked) InvocationTargetException.

换句话说，它可以打败受检异常系统.

In other words, it can defeat the checked exceptions system.

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