关灯
开启左侧

Java 反射机制的用途和缺点

[复制链接]
大雨滂沱 发表于 2018-6-8 09:35:05 | 显示全部楼层 |阅读模式 打印 上一主题 下一主题
 
反射的用途 Uses of Reflection
Reflection is commonly used by programs which require the ability to examine or modify the runtime behavior of applications running in the Java virtual machine. This is a relatively advanced feature and should be used only by developers who have a strong grasp of the fundamentals of the language. With that caveat in mind, reflection is a powerful technique and can enable applications to perform operations which would otherwise be impossible.
反射被广泛地用于那些需要在运行时检测或修改程序行为的程序中。这是一个相对高级的特性,只有那些语言基础非常扎实的开发者才应该使用它。如果能把这句警示时刻放在心里,那么反射机制就会成为一项强大的技术,可以让应用程序做一些几乎不可能做到的事情。

反射的缺点 Drawbacks of Reflection
Reflection is powerful, but should not be used indiscriminately. If it is possible to perform an operation without using reflection, then it is preferable to avoid using it. The following concerns should be kept in mind when accessing code via reflection.
尽管反射非常强大,但也不能滥用。如果一个功能可以不用反射完成,那么最好就不用。
在我们使用反射技术时,下面几条内容应该牢记于心:

1.性能第一 Performance Overhead
Because reflection involves types that are dynamically resolved, certain Java virtual machine optimizations can not be performed. Consequently, reflective operations have slower performance than their non-reflective counterparts, and should be avoided in sections of code which are called frequently in performance-sensitive applications.
反射包括了一些动态类型,所以 JVM 无法对这些代码进行优化。因此,反射操作的效率要比那些非反射操作低得多。我们应该避免在经常被 执行的代码或对性能要求很高的程序中使用反射。
2.安全限制 Security Restrictions
Reflection requires a runtime permission which may not be present when running under a security manager. This is in an important consideration for code which has to run in a restricted security context, such as in an Applet.
使用反射技术要求程序必须在一个没有安全限制的环境中运行。如果一个程序必须在有安全限制的环境中运行,如 Applet,那么这就是个问题了。
3.内部暴露 Exposure of Internals
Since reflection allows code to perform operations that would be illegal in non-reflective code, such as accessing private fields and methods, the use of reflection can result in unexpected side-effects, which may render code dysfunctional and may destroy portability. Reflective code breaks abstractions and therefore may change behavior with upgrades of the platform.
由于反射允许代码执行一些在正常情况下不被允许的操作(比如访问私有的属性和方法),所以使用反射可能会导致意料之外的副作用——代码有功能上的错误,降低可移植性。反射代码破坏了抽象性,因此当平台发生改变的时候,代码的行为就有可能也随着变化。





 

精彩评论1

正序浏览
意大利炮 发表于 2018-8-20 13:13:23 来自手机 | 显示全部楼层
 
顶老大6666666666666666
 
您需要登录后才可以回帖 登录 | 立即注册

本版积分规则

  • 最佳新人

    注册账号后积极发帖的会员

0关注

8粉丝

6帖子

排行榜
关闭

站长推荐上一条 /1 下一条

官方微信

全国服务热线:

400-0708-360

公司地址:国家西部信息安全产业基地(成都市高新区云华路333号)

邮编:610000    Email:2908503813@qq.com

Copyright   ©2015-2016  EOIT论坛Powered by©Discuz!    ( 蜀ICP备11000634号-7 )