blocks|key|1351592|text|根据维基百科的定义，术语"shim“在技术上可以被归类为”结构化“设计模式。许多类型的“结构化”设计模式在(有些人会说是事实上的)面向对象软件设计模式参考"Design+Patterns,+Elements+of+Reusable+Object-Oriented+Software"+(更为人所知的是"Gang+of+Four"+)中有非常清晰的描述。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1351593|"Gang+of+Four"文本概述了至少3种公认的模式，即“代理”、“适配器”和“门面”，它们都提供了“填充”类型的功能。在大多数领域中，经常会使用和/或遗漏使用同一根概念的不同缩写词，这会导致人们感到困惑。使用“填充”这个词来描述更具体的“结构化”设计模式"Proxy"、"Adapter"和"Facade"无疑就是这种情况的一个明显的例子。"shim“只是一个更一般的术语，表示更具体类型的”结构化“模式”代理“、”适配器“、”外观“以及其他可能的类型。|1351594|entityMap|0|LINK|mutability|MUTABLE|url|https://en.wikipedia.org/wiki/Design_Patterns|1|2|3|https://en.wikipedia.org/?title=Proxy_pattern|4|https://en.wikipedia.org/wiki/Adapter_pattern|5|https://en.wikipedia.org/wiki/Facade_pattern^0|25|1S|0|46|E|1|0|0|E|2|3M|7|3|3U|9|4|44|8|5|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@$A|W|B|X|1|Y]|$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@$A|13|B|14|1|15]|$A|16|B|17|1|18]|$A|19|B|1A|1|1B]|$A|1C|B|1D|1|1E]]|C|$]]|$1|F|3|-4|5|6|7|1F|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|M]]|O|$5|I|J|K|C|$L|M]]|P|$5|I|J|K|C|$L|Q]]|R|$5|I|J|K|C|$L|S]]|T|$5|I|J|K|C|$L|U]]]]

The term "shim" as defined in Wikipedia would technically be classified, based on its definition, as a "Structural" design pattern. The many types of “Structural” design patterns are quite clearly described in the (some would say defacto) object oriented software design patterns reference <a href="https://en.wikipedia.org/wiki/Design_Patterns" rel="noreferrer">"Design Patterns, Elements of Reusable Object-Oriented Software"</a> better known as the <a href="https://en.wikipedia.org/wiki/Design_Patterns" rel="noreferrer">"Gang of Four"</a>. 

The <a href="https://en.wikipedia.org/wiki/Design_Patterns" rel="noreferrer">"Gang of Four"</a> text outlines at least 3 well established patterns known as, "Proxy", "Adapter" and "Facade" which all provide “shim” type functionality. In most fields it’s often times the use and or miss use of different acronyms for the same root concept that causes people confusion. Using the word “shim” to describe the more specific “Structural” design patterns <a href="https://en.wikipedia.org/?title=Proxy_pattern" rel="noreferrer">"Proxy"</a>, <a href="https://en.wikipedia.org/wiki/Adapter_pattern" rel="noreferrer">"Adapter"</a> and <a href="https://en.wikipedia.org/wiki/Facade_pattern" rel="noreferrer">"Facade"</a> certainly is a clear example of this type of situation. A "shim" is simply a more general term for the more specific types of "Structural" patterns "Proxy", "Adapter", "Facade" and possibly others.

blocks|key|1136176|text|至于这个词的起源，苹果公司的Dictionary小工具说|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1136177|noun
+++a+washer+or+thin+strip+of+material+used+to+align+parts,+
+++make+them+fit,+or+reduce+wear.

verb+(+shimmed,+shimming)+[+trans.+]
+++wedge+(something)+or+fill+up+(a+space)+with+a+shim.

ORIGIN+early+18th+cent.:+of+unknown+origin|code-block|syntax|javascript|1136178|这似乎非常符合网页设计师使用这个术语的方式。|1136179|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

As for origins of the word, quoth Apple's Dictionary widget

<pre><code>noun
 a washer or thin strip of material used to align parts, 
 make them fit, or reduce wear.

verb ( shimmed, shimming) [ trans. ]
 wedge (something) or fill up (a space) with a shim.

ORIGIN early 18th cent.: of unknown origin
</code></pre>

This seems to fit quite well with how web designers use the term.

blocks|key|1136195|text|.net+4.5+Microsoft+Fakes框架to+isolate+your+application+from+other+assemblies+for+unit+testing中使用了填充符。填充符将对特定方法的调用转移到您作为测试的一部分编写的代码中|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1136196|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/hh549176.aspx^0|Q|1U|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Shims are used in .net 4.5 Microsoft Fakes framework <a href="http://msdn.microsoft.com/en-us/library/hh549176.aspx" rel="noreferrer">to isolate your application from other assemblies for unit testing</a>. Shims divert calls to specific methods to code that you write as part of your test

blocks|key|1351656|text|正如我们在这里的许多响应中所看到的，填充程序是一种在API级别提供功能的适配器，而API级别的功能不一定是该API的一部分。这个线程有很多好的和完整的响应，所以我不会进一步扩展这个定义。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1351657|然而，我想我可以添加一个很好的例子，那就是Javascript+ES5+Shim+(https://github.com/es-shims/es5-shim)：|offset|length|1351658|Javascript在过去的几年中发生了很大的变化，在语言规范的其他变化中，许多新方法被添加到它的核心对象中。|1351659|例如，在ES2015规范(又称ES5)中，find方法被添加到Array原型中。因此，假设您正在使用本规范(例如:Node0.12)之前的JavasScript引擎运行代码，该规范还没有提供该方法。通过加载ES5填充程序，这些新方法将被添加到Array原型中，即使您没有在较新的JavaScript规范上运行，也可以使用它们。|style|CODE|1351660|您可能会问:为什么有人要这样做，而不是将环境升级到更新的版本(比方说Node+8)？|1351661|在很多实际案例中，这种方法是有意义的。一个很好的例子：|1351662|假设您有一个在旧环境中运行的遗留系统，并且您需要使用这些新方法来实现/修复功能。您的环境的升级仍在进行中，因为存在兼容性问题，需要进行大量的代码更改和测试(一个关键组件)。|1351663|在本例中，您可以尝试制作此类功能的您自己的版本，但这将使您的代码更难阅读，更复杂，可能会引入新的错误，并将需要大量额外的测试，仅仅是为了涵盖您知道将在下一个版本中提供的功能。|1351664|相反，您可以使用此填充程序并利用这些新方法，利用此修复程序/功能将在升级后兼容的事实，因为您已经在使用下一个规范中已知的可用方法。还有一个额外的原因:因为这些方法是下一种语言规范的原生方法，所以它们的运行速度很可能比您尝试创建自己的版本时的任何实现都要快。|1351665|这种方法受欢迎的另一个实际场景是在浏览器级别。假设您需要支持旧浏览器，并希望利用这些新功能。Javascript是一种允许您在其核心对象中添加/修改方法的语言(如将方法添加到Array+prototype中)，而这些填充库仅在当前实现缺少此类方法时才会智能地添加这些方法。|1351666|PS:+1)您将看到与这些Javascript填充符相关的术语"Polyfill“。Polyfill是一种更专业的填充类型，用于在不同的浏览器级别规范中提供前向兼容性。顺便说一下，我上面的例子就是这样的例子。|1351667|2)垫片不限于此示例(添加将在未来版本中提供的功能)。还有一些不同的用例也会被认为是填充程序。|1351668|3)如果您对这个特定的polyfill是如何实现的很好奇，您可以打开Javascript+Array.find规范并滚动到页面末尾，在那里您将找到此方法的规范实现。|1351669|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/es-shims/es5-shim|1|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find^0|0|16|10|0|0|0|L|4|V|5|3D|5|0|0|0|0|0|0|0|0|0|19|A|1|0^^$0|@$1|2|3|4|5|6|7|1D|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1E|8|@]|9|@$D|1F|E|1G|1|1H]]|A|$]]|$1|F|3|G|5|6|7|1I|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|1J|8|@$D|1K|E|1L|J|K]|$D|1M|E|1N|J|K]|$D|1O|E|1P|J|K]]|9|@]|A|$]]|$1|L|3|M|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1R|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1S|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|1T|8|@]|9|@]|A|$]]|$1|T|3|U|5|6|7|1U|8|@]|9|@]|A|$]]|$1|V|3|W|5|6|7|1V|8|@]|9|@]|A|$]]|$1|X|3|Y|5|6|7|1W|8|@]|9|@]|A|$]]|$1|Z|3|10|5|6|7|1X|8|@]|9|@]|A|$]]|$1|11|3|12|5|6|7|1Y|8|@]|9|@$D|1Z|E|20|1|21]]|A|$]]|$1|13|3|-4|5|6|7|22|8|@]|9|@]|A|$]]]|14|$15|$5|16|17|18|A|$19|1A]]|1B|$5|16|17|18|A|$19|1C]]]]

As we could see in many responses here, a shim is a sort of adapter that provides functionality at API level which was not necessarily part of that API. This thread has a lot of good and complete responses, so I'm not expanding the definition further.

However, I think I can add a good example, which is the Javascript ES5 Shim (<a href="https://github.com/es-shims/es5-shim" rel="nofollow noreferrer">https://github.com/es-shims/es5-shim</a>):

Javascript has evolved a lot during the last few years, and among many other changes to the language specification, a lot of new methods have been added to its core objects.

For example, in the ES2015 specification (aka ES5), the method <code>find</code> has been added to the <code>Array</code> prototype. So let's say you are running your code using a JavasScript engine prior to this specification (ex: Node 0.12) which doesn't offer that method yet. By loading the ES5 shim, these new methods will be added to the <code>Array</code> prototype, allowing you to make use of them even if you are not running on a newer JavaScript specification.

You might ask: why would someone do that instead of upgrading the environment to a newer version (let's say Node 8)?

There is a lot of real cases scenarios where that approach makes sense. One good example:

Let's say you have a legacy system that is running in an old environment, and you need to use such new methods to implement/fix a functionality. The upgrade of your environment still a work in progress because there are compatibility issues that require a lot of code changes and tests (a critical component).

In this example, you could try to craft your own version of such functionality, but that would make your code harder to read, more complex, can introduce new bugs and will require tons of additional tests just to cover a functionality that you know it will be available in the next release.

Instead, you can use this shim and make use of these new methods, taking advantage of the fact that this fix/functionality will be compatible after the upgrade, because you are already using the methods known to be available in the next specification. And there is a bonus reason: since these methods are native to the next language specification, there is a good chance that they will run faster than any implementation that you could have done if you tried to make your own version.

Another real scenario where such approach is welcome is at browser level. Let's say you need to support old browser and want to take advantage of these newer features. Javascript is a language that allows you to add/modify methods in its core objects (like adding methods to Array prototype), and those shim libraries are smart enough to add such methods only if the current implementation is lacking of them. 

PS:
1) You will see the term "Polyfill" related to these Javascript shims. Polyfill is a more specialized type of shim that is used to provide forward compatibility in different browser level specifications. By the way, my example above refers exactly to such example.

2) Shims are not limited to this example (adding functionality that will be available in a future release). There are different use cases that would be considered to be a shim as well.

3) If you are curious about how this specific polyfill is implemented, you can open Javascript <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find" rel="nofollow noreferrer">Array.find</a> specs and scroll to the end of the page where you will find a canonical implementation for this method.

blocks|key|1351694|text|填充是对所有服务执行的另一种级别的安全检查，以保护上游系统。SHIM+Server根据在请求(SOAP/+RESTFUL)中传递的用户凭据来验证每个传入请求，其中包含头用户凭据。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1351695|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

SHIM is another level of security check which is done for all the services, to protect upstream systems. SHIM Server validates every incoming request, with Headers User credentials, against the user credentials, which are passed in the request(SOAP / RESTFUL).

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