我们先来看看需要重构的功能是一个下拉选择框，可任意选择11部词典中的一部，访问地址：http://123.56.99.179/select/dictionary-select.jsp?dict=RANDOMHOUSE，在HTML中的效果如下图所示：
HTML代码如下：
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<select?name="dict"?id="dict"?onchange="update();">
?
????<option?value="ICIBA">iCIBA</option>
????<option?value="YOUDAO">Youdao</option>
????<option?value="COLLINS">Collins</option>
????<option?value="WEBSTER">Webster‘s</option>
????<option?value="OXFORD">Oxford</option>
????<option?value="CAMBRIDGE">Cambridge</option>
????<option?value="MACMILLAN">Macmillan</option>
????<option?value="HERITAGE">Heritage</option>
????<option?value="WIKTIONARY">Wiktionary</option>
????<option?value="WORDNET">WordNet</option>
????<option?value="RANDOMHOUSE"?selected="selected">RandomHouse</option>
?
</select>
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?
我们接下来看看最初的JSP代码是如何实现这个功能的：
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<%@?page?contentType="text/html;charset=UTF-8"?language="java"?%>
<%@?page?import="org.apdplat.superword.tools.WordLinker"?%>
<%@?page?import="org.apdplat.superword.tools.WordLinker.Dictionary"?%>
?
????????<select?name="dict"?id="dict"?onchange="update();">
????<%
????????if?(Dictionary.ICIBA==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA"?selected="selected">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.YOUDAO==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO"?selected="selected">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.COLLINS==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS"?selected="selected">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.WEBSTER==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER"?selected="selected">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.OXFORD==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD"?selected="selected">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.CAMBRIDGE==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE"?selected="selected">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.MACMILLAN==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN"?selected="selected">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.HERITAGE==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE"?selected="selected">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.WIKTIONARY==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY"?selected="selected">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????????????<%
????}?else?if?(Dictionary.WORDNET==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET"?selected="selected">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.RANDOMHOUSE==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">爱词霸</option>
????????????<option?value="YOUDAO">有道</option>
????????????<option?value="COLLINS">柯林斯</option>
????????????<option?value="WEBSTER">韦氏</option>
????????????<option?value="OXFORD">牛津</option>
????????????<option?value="CAMBRIDGE">剑桥</option>
????????????<option?value="MACMILLAN">麦克米伦</option>
????????????<option?value="HERITAGE">美国传统</option>
????????????<option?value="WIKTIONARY">维基词典</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE"?selected="selected">RandomHouse</option>
????<%
????}
????%>
????????</select>
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?
?
这段代码有什么问题呢？
如果我们一次写好后就不需要维护和更改这段代码，那么根据自己的经验知识和理解快速实现功能，满足要求即可。
但是，如果需要维护代码和扩展功能呢？比如，我现在要把选项显示的所有的中文全部改为英文，那么就变成如下代码了：
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????????<select?name="dict"?id="dict"?onchange="update();">
????<%
????????if?(Dictionary.ICIBA==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA"?selected="selected">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.YOUDAO==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO"?selected="selected">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.COLLINS==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS"?selected="selected">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.WEBSTER==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER"?selected="selected">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.OXFORD==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD"?selected="selected">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.CAMBRIDGE==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE"?selected="selected">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.MACMILLAN==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN"?selected="selected">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.HERITAGE==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE"?selected="selected">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.WIKTIONARY==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY"?selected="selected">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????????????<%
????}?else?if?(Dictionary.WORDNET==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET"?selected="selected">WordNet</option>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????<%
????}?else?if?(Dictionary.RANDOMHOUSE==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????%>
????????????<option?value="ICIBA">iCIBA</option>
????????????<option?value="YOUDAO">Youdao</option>
????????????<option?value="COLLINS">Collins</option>
????????????<option?value="WEBSTER">Webster‘s</option>
????????????<option?value="OXFORD">Oxford</option>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????????<option?value="MACMILLAN">Macmillan</option>
????????????<option?value="HERITAGE">Heritage</option>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????????<option?value="WORDNET">WordNet</option>
????????????<option?value="RANDOMHOUSE"?selected="selected">RandomHouse</option>
????<%
????}
????%>
????????</select>
|
?
?
你可能说，我只需要执行 CTRL+R 11次，没啥问题啊？其实这恰恰就是问题，因为同样的字符串重复了11次。
改成了英文名称之后，接下来，如果我们要新增一个选项怎么办呢？我们不但需要复制粘贴代码来新增一个ELSE IF代码块，我们还需要修改既有的11个IF代码块，都新增一个option。这不但违反了DRY原则，也违反了开闭原则。下面开始来改造，改造后的代码如下：
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????<select?name="dict"?id="dict"?onchange="update();">
????????<%
????????if?(Dictionary.ICIBA==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="ICIBA"?selected="selected">iCIBA</option>
????????<%
????????}?else?{
????????%>
????????<option?value="ICIBA">iCIBA</option>
????????<%
????????}
????????if?(Dictionary.YOUDAO==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="YOUDAO"?selected="selected">Youdao</option>
????????<%
????????}?else?{
????????%>
????????<option?value="YOUDAO">Youdao</option>
????????<%
????????}
????????if?(Dictionary.COLLINS==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="COLLINS"?selected="selected">Collins</option>
????????<%
????????}?else?{
????????%>
????????<option?value="COLLINS">Collins</option>
????????<%
????????}
????????if?(Dictionary.WEBSTER==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="WEBSTER"?selected="selected">Webster‘s</option>
????????<%
????????}?else?{
????????%>
????????<option?value="WEBSTER">Webster‘s</option>
????????<%
????????}
????????if?(Dictionary.OXFORD==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="OXFORD"?selected="selected">Oxford</option>
????????<%
????????}?else?{
????????%>
????????<option?value="OXFORD">Oxford</option>
????????<%
????????}
????????if?(Dictionary.CAMBRIDGE==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="CAMBRIDGE"?selected="selected">Cambridge</option>
????????<%
????????}?else?{
????????%>
????????<option?value="CAMBRIDGE">Cambridge</option>
????????<%
????????}
????????if?(Dictionary.MACMILLAN==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="MACMILLAN"?selected="selected">Macmillan</option>
????????<%
????????}?else?{
????????%>
????????<option?value="MACMILLAN">Macmillan</option>
????????<%
????????}
????????if?(Dictionary.HERITAGE==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="HERITAGE"?selected="selected">Heritage</option>
????????<%
????????}?else?{
????????%>
????????<option?value="HERITAGE">Heritage</option>
????????<%
????????}
????????if?(Dictionary.WIKTIONARY==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="WIKTIONARY"?selected="selected">Wiktionary</option>
????????<%
????????}?else?{
????????%>
????????<option?value="WIKTIONARY">Wiktionary</option>
????????<%
????????}
????????if?(Dictionary.WORDNET==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="WORDNET"?selected="selected">WordNet</option>
????????<%
????????}?else?{
????????%>
????????<option?value="WORDNET">WordNet</option>
????????<%
????????}
????????if?(Dictionary.RANDOMHOUSE==WordLinker.getValidDictionary(request.getParameter("dict")))?{
????????%>
????????<option?value="RANDOMHOUSE"?selected="selected">RandomHouse</option>
????????<%
????????}?else?{
????????%>
????????<option?value="RANDOMHOUSE">RandomHouse</option>
????????<%
????????}
????????%>
????</select>
|
?
?
重构代码后是不是可读性降低了？原来的代码虽然违反了DRY原则和开闭原则，但是可读性却是极好的。即使如此，重构后的代码却是非常容易扩展，新增选项只需要增加一个IF代码块即可，不需要修改现有的IF代码块，符合了开闭原则，同时移除了重复了11次的option，所以虽然可读性降低了，但是却完美达成了DRY原则和开闭原则。
这个例子说明了一个非常重要的道理，具体的东西更容易让人理解，而更抽象的东西理解起来就要更费劲，所以，我们在写代码的时候，一开始完全没有必要满脑子的各种最佳实践，各种设计模式，各种架构模式，最佳实践设计模式架构模式都有限制的场景，他们都应该是重构自然而然的结果，一开始就考虑这些东西，不但会拖慢功能实现的速度，而且往往会陷于“过度设计”、“不成熟的优化”的泥淖。
上面的代码还不够彻底，还存在重复，接着重构来贯彻DRY原则：
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????<select?name="dict"?id="dict"?onchange="update();">
????????<%
????????Dictionary?selectedDictionary?=?WordLinker.getValidDictionary(request.getParameter("dict"));
????????if?(Dictionary.ICIBA?==?selectedDictionary)?{
????????%>
????????????<option?value="ICIBA"?selected="selected">iCIBA</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="ICIBA">iCIBA</option>
????????<%
????????}
?
????????if?(Dictionary.YOUDAO?==?selectedDictionary)?{
????????%>
????????????<option?value="YOUDAO"?selected="selected">Youdao</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="YOUDAO">Youdao</option>
????????<%
????????}
?
????????if?(Dictionary.COLLINS?==?selectedDictionary)?{
????????%>
????????????<option?value="COLLINS"?selected="selected">Collins</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="COLLINS">Collins</option>
????????<%
????????}
?
????????if?(Dictionary.WEBSTER?==?selectedDictionary)?{
????????%>
????????????<option?value="WEBSTER"?selected="selected">Webster‘s</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="WEBSTER">Webster‘s</option>
????????<%
????????}
?
????????if?(Dictionary.OXFORD?==?selectedDictionary)?{
????????%>
????????????<option?value="OXFORD"?selected="selected">Oxford</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="OXFORD">Oxford</option>
????????<%
????????}
?
????????if?(Dictionary.CAMBRIDGE?==?selectedDictionary)?{
????????%>
????????????<option?value="CAMBRIDGE"?selected="selected">Cambridge</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="CAMBRIDGE">Cambridge</option>
????????<%
????????}
?
????????if?(Dictionary.MACMILLAN?==?selectedDictionary)?{
????????%>
????????????<option?value="MACMILLAN"?selected="selected">Macmillan</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="MACMILLAN">Macmillan</option>
????????<%
????????}
?
????????if?(Dictionary.HERITAGE?==?selectedDictionary)?{
????????%>
????????????<option?value="HERITAGE"?selected="selected">Heritage</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="HERITAGE">Heritage</option>
????????<%
????????}
?
????????if?(Dictionary.WIKTIONARY?==?selectedDictionary)?{
????????%>
????????????<option?value="WIKTIONARY"?selected="selected">Wiktionary</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="WIKTIONARY">Wiktionary</option>
????????<%
????????}
?
????????if?(Dictionary.WORDNET?==?selectedDictionary)?{
????????%>
????????????<option?value="WORDNET"?selected="selected">WordNet</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="WORDNET">WordNet</option>
????????<%
????????}
?
????????if?(Dictionary.RANDOMHOUSE?==?selectedDictionary)?{
????????%>
????????????<option?value="RANDOMHOUSE"?selected="selected">RandomHouse</option>
????????<%
????????}?else?{
????????%>
????????????<option?value="RANDOMHOUSE">RandomHouse</option>
????????<%
????????}
????????%>
????</select>
|
?
?
这次，我们把重复的代码抽取为一个变量，并在IF代码块前面加了一个空行，看上去是不是可读性提高了？这也说明了DRY原则对于代码的简洁和易读是有帮助的，同时也说明了我们编写的代码的换行缩进等风格对可读性也是有影响的，作为一个有尊严的程序员，需要注意这些细节，细节决定成败，成功者往往只是比对手多做了一点而已，而多做的这一点，往往就是在细节上面。
虽然易读性有了提高，但是还是比较糟糕，离生成的HTML的差距还很大，下面继续重构，结果如下：
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<%????Dictionary?selectedDictionary?=?WordLinker.getValidDictionary(request.getParameter("dict"));
????String?ICIBA?=?"";
????String?YOUDAO?=?"";
????String?COLLINS?=?"";
????String?WEBSTER?=?"";
????String?OXFORD?=?"";
????String?CAMBRIDGE?=?"";
????String?MACMILLAN?=?"";
????String?HERITAGE?=?"";
????String?WIKTIONARY?=?"";
????String?WORDNET?=?"";
????String?RANDOMHOUSE?=?"";
????String?selected?=?"selected=\"selected\"";
????switch?(selectedDictionary){
????????case?ICIBA:
????????????ICIBA?=?selected;?break;
????????case?YOUDAO:
????????????YOUDAO?=?selected;?break;
????????case?COLLINS:
????????????COLLINS?=?selected;?break;
????????case?WEBSTER:
????????????WEBSTER?=?selected;?break;
????????case?OXFORD:
????????????OXFORD?=?selected;?break;
????????case?CAMBRIDGE:
????????????CAMBRIDGE?=?selected;?break;
????????case?MACMILLAN:
????????????MACMILLAN?=?selected;?break;
????????case?HERITAGE:
????????????HERITAGE?=?selected;?break;
????????case?WIKTIONARY:
????????????WIKTIONARY?=?selected;?break;
????????case?WORDNET:
????????????WORDNET?=?selected;?break;
????????case?RANDOMHOUSE:
????????????RANDOMHOUSE?=?selected;?break;
????}
%><select?name="dict"?id="dict"?onchange="update();">
????<option?value="ICIBA"?<%=ICIBA%>>iCIBA</option>
????<option?value="YOUDAO"?<%=YOUDAO%>>Youdao</option>
????<option?value="COLLINS"?<%=COLLINS%>>Collins</option>
????<option?value="WEBSTER"?<%=WEBSTER%>>Webster‘s</option>
????<option?value="OXFORD"?<%=OXFORD%>>Oxford</option>
????<option?value="CAMBRIDGE"?<%=CAMBRIDGE%>>Cambridge</option>
????<option?value="MACMILLAN"?<%=MACMILLAN%>>Macmillan</option>
????<option?value="HERITAGE"?<%=HERITAGE%>>Heritage</option>
????<option?value="WIKTIONARY"?<%=WIKTIONARY%>>Wiktionary</option>
????<option?value="WORDNET"?<%=WORDNET%>>WordNet</option>
????<option?value="RANDOMHOUSE"?<%=RANDOMHOUSE%>>RandomHouse</option>
</select> |
?
?
这次重构过后，看起来是不是跟最终生成的HTML差别已经不大了？易读性有了质的飞跃，但是你有没有发现，这里面还是有很多重复，而且存在着模式和规律，我们可以再继续重构吗？
肯定可以，直接看重构后的结果吧：
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????<select?name="dict"?id="dict"?onchange="update();">
????????<%
????????Dictionary?selectedDictionary?=?WordLinker.getValidDictionary(request.getParameter("dict"));
????????for(Dictionary?dictionary?:?Dictionary.values()){
????????????if?(dictionary?==?selectedDictionary)?{
????????%>
????????????<option?value="<%=dictionary.name()%>"?selected="selected"><%=dictionary.getDes()%></option>
????????<%
????????????}?else?{
????????%>
????????????<option?value="<%=dictionary.name()%>"><%=dictionary.getDes()%></option>
????????<%
????????????}
????????}
????????%>
????</select>
|
?
?
这次，我们直接遍历数据模型Dictionary，从而完全消除了重复，同时在开闭原则上也有了新的高度，以后当我们需要扩展新的选项的时候，我们已经不再需要修改哪怕一行代码了。
?
那如果我们不是需要Dictionary的所有选项怎么办呢？这肯定也不是问题，解决方法如下：
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<%!????private?static?final?List<Dictionary>?DICTIONARIES?=?Arrays.asList(Dictionary.ICIBA,?Dictionary.YOUDAO,?Dictionary.WEBSTER,?Dictionary.OXFORD);
%><select?name="dictionary"?id="dictionary"?onchange="update();">
????<%
????????Dictionary?selectedDictionary?=?WordLinker.getValidDictionary(request.getParameter("dictionary"));
????????for(Dictionary?dictionary?:?DICTIONARIES){
????????????if?(dictionary?==?selectedDictionary)?{
????%>
????<option?value="<%=dictionary.name()%>"?selected="selected"><%=dictionary.getDes()%></option>
????<%
????}?else?{
????%>
????<option?value="<%=dictionary.name()%>"><%=dictionary.getDes()%></option>
????<%
????????????}
????????}
????%>
</select> |
?
?
一次完美的重构就此结束，要想尝试更多的重构工作，敬请加入到superword的重构中来：https://github.com/ysc/superword
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原文：http://yangshangchuan.iteye.com/blog/2292986