编码至高法则-高内聚低耦合
此法则适合所有语言，咱们以JavaScript和Java两个角度分析一下这个东东。
一、javascript
有这样的一个页面，js、css代码都写在html页面中。
例如：gnj.html
v1版本
[HTML] 纯文本查看 复制代码
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<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta http-equiv="X-UA-Compatible" content="ie=edge"><title>Document</title></head><body><script>document.write("高内聚低耦合demo");</script><style>h1 {}</style><h1>标题</h1></body></html> |
这个页面承载了多个功能：定义html需要的javascript脚本，定义html需要的css样式，还有定义页面需要显示的元素。
这样的代码编写方式就像下面两个拼拼凑凑的动物：
龙：
<ignore_js_op>
角似鹿、头似牛、眼似虾、嘴似驴、腹似蛇、鳞似鱼、足似凤、须似人、耳似象
麋鹿：
<ignore_js_op>
角似鹿非鹿、鼻子似牛非牛、身体似驴非驴、尾巴似马非马
问题：代码内部比较臃肿，复用度很低。js不能被多个html复用，css也不能被多个html复用。耦合性较高。
优化后的代码，如下：
v2版本
gnj.js
[JavaScript] 纯文本查看 复制代码
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document.write("高内聚低耦合demo"); |
h1.css
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h1 { } |
gnj_v2.html
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<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> <script src="./gnj.js"></script> <link rel="stylesheet" type="text/css" href="h1.css"/></head><body> <h1>标题</h1></body></html> |
高内聚：模块内的事。模块内，联系越紧密，内聚性越高。
低耦合:模块间的事，相关的操作，不再直接相互依赖调用
二、java
再来看一个java的中午吃饭过程的例子：
v0版本
[Java] 纯文本查看 复制代码
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package com.gavin.controller;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RestController;/*** Created by 传智播客.黑马程序员.太原校区.苗雄 on 2019\8\30*/@RestControllerpublic class DemoController { @GetMapping("/lunch") public String haveLunch(){ StringBuilder builder = new StringBuilder(); builder.append("<html>"); //排队 builder.append(String.format("%s <br/>","--------------------------------------------")); builder.append(String.format("%s <br/>","(^o^)开始排队(^o^)")); builder.append(String.format("%s <br/>","1只羊")); builder.append(String.format("%s <br/>","2只羊")); builder.append(String.format("%s <br/>","3只羊")); builder.append(String.format("%s <br/>","4只羊")); builder.append(String.format("%s <br/>","5只羊")); builder.append(String.format("%s <br/>","6只羊")); builder.append(String.format("%s <br/>","7只羊")); builder.append(String.format("%s <br/>","8只羊")); builder.append(String.format("%s <br/>","9只羊")); builder.append(String.format("%s <br/>","(-o-)结束排队(-o-)")); //点菜 builder.append(String.format("%s <br/>","--------------------------------------------")); builder.append(String.format("%s <br/>","(^o^)开始点菜(^o^)")); builder.append(String.format("%s <br/>","蒸羊羔")); builder.append(String.format("%s <br/>","蒸熊掌")); builder.append(String.format("%s <br/>","蒸鹿尾儿")); builder.append(String.format("%s <br/>","烧花鸭")); builder.append(String.format("%s <br/>","烧雏鸡")); builder.append(String.format("%s <br/>","烧子鹅")); builder.append(String.format("%s <br/>","卤猪")); builder.append(String.format("%s <br/>","卤鸭")); builder.append(String.format("%s <br/>","酱鸡")); builder.append(String.format("%s <br/>","腊肉")); builder.append(String.format("%s <br/>","松花")); builder.append(String.format("%s <br/>","小肚儿")); builder.append(String.format("%s <br/>","(-o-)结束点菜(-o-)")); //取餐 builder.append(String.format("%s <br/>","--------------------------------------------")); builder.append(String.format("%s <br/>","(^o^)开始取餐(^o^)")); builder.append(String.format("%s <br/>","一盘蒸羊羔")); builder.append(String.format("%s <br/>","一盘蒸熊掌")); builder.append(String.format("%s <br/>","一盘蒸鹿尾儿")); builder.append(String.format("%s <br/>","一盘烧花鸭")); builder.append(String.format("%s <br/>","一盘烧雏鸡")); builder.append(String.format("%s <br/>","一盘烧子鹅")); builder.append(String.format("%s <br/>","一盘卤猪")); builder.append(String.format("%s <br/>","一盘卤鸭")); builder.append(String.format("%s <br/>","一盘酱鸡")); builder.append(String.format("%s <br/>","一盘腊肉")); builder.append(String.format("%s <br/>","一盘松花")); builder.append(String.format("%s <br/>","一盘小肚儿")); builder.append(String.format("%s <br/>","(-o-)结束取餐(-o-)")); //用餐 builder.append(String.format("%s <br/>","--------------------------------------------")); builder.append(String.format("%s <br/>","(^o^)开始用餐(^o^)")); builder.append(String.format("%s <br/>","蒸羊羔好吃")); builder.append(String.format("%s <br/>","蒸熊掌好吃")); builder.append(String.format("%s <br/>","蒸鹿尾儿好吃")); builder.append(String.format("%s <br/>","烧花鸭好吃")); builder.append(String.format("%s <br/>","烧雏鸡好吃")); builder.append(String.format("%s <br/>","烧子鹅好吃")); builder.append(String.format("%s <br/>","卤猪好吃")); builder.append(String.format("%s <br/>","卤鸭好吃")); builder.append(String.format("%s <br/>","酱鸡好吃")); builder.append(String.format("%s <br/>","腊肉好吃")); builder.append(String.format("%s <br/>","松花好吃")); builder.append(String.format("%s <br/>","小肚儿好吃")); builder.append(String.format("%s <br/>","(-o-)结束用餐(-o-)")); builder.append(String.format("%s <br/>","--------------------------------------------")); builder.append("</html>"); return builder.toString(); }} |
代码运行如下：
<ignore_js_op>
仔细阅读以上代码，发现有很多重复的地方，比如分割线和添加字符串操作。基于这两个重复的地方，咱们可以优化一下。单独提供两个方法，一个获取分割线，另外一个处理字符串拼接。
V1版本
[Java] 纯文本查看 复制代码
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package com.gavin.controller;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RestController;/*** Created by 传智播客.黑马程序员.太原校区.苗雄 on 2019\8\30*/@RestControllerpublic class DemoV1Controller { @GetMapping("/v1/lunch") public String haveLunch(){ StringBuilder builder = new StringBuilder(); builder.append("<html>"); //排队 appendStr(builder,getSeparator()); appendStr(builder,"(^o^)开始排队(^o^)"); appendStr(builder,"1只羊"); appendStr(builder,"2只羊"); appendStr(builder,"3只羊"); appendStr(builder,"4只羊"); appendStr(builder,"5只羊"); appendStr(builder,"6只羊"); appendStr(builder,"7只羊"); appendStr(builder,"8只羊"); appendStr(builder,"9只羊"); appendStr(builder,"(-o-)结束排队(-o-)"); //点菜 appendStr(builder,getSeparator()); appendStr(builder,"(^o^)开始点菜(^o^)"); appendStr(builder,"蒸羊羔"); appendStr(builder,"蒸熊掌"); appendStr(builder,"蒸鹿尾儿"); appendStr(builder,"烧花鸭"); appendStr(builder,"烧雏鸡"); appendStr(builder,"烧子鹅"); appendStr(builder,"卤猪"); appendStr(builder,"卤鸭"); appendStr(builder,"酱鸡"); appendStr(builder,"腊肉"); appendStr(builder,"松花"); appendStr(builder,"小肚儿"); appendStr(builder,"(-o-)结束点菜(-o-)"); //取餐 appendStr(builder,getSeparator()); appendStr(builder,"(^o^)开始取餐(^o^)"); appendStr(builder,"一盘蒸羊羔"); appendStr(builder,"一盘蒸熊掌"); appendStr(builder,"一盘蒸鹿尾儿"); appendStr(builder,"一盘烧花鸭"); appendStr(builder,"一盘烧雏鸡"); appendStr(builder,"一盘烧子鹅"); appendStr(builder,"一盘卤猪"); appendStr(builder,"一盘卤鸭"); appendStr(builder,"一盘酱鸡"); appendStr(builder,"一盘腊肉"); appendStr(builder,"一盘松花"); appendStr(builder,"一盘小肚儿"); appendStr(builder,"(-o-)结束取餐(-o-)"); //用餐 appendStr(builder,getSeparator()); appendStr(builder,"(^o^)开始用餐(^o^)"); appendStr(builder,"蒸羊羔好吃"); appendStr(builder,"蒸熊掌好吃"); appendStr(builder,"蒸鹿尾儿好吃"); appendStr(builder,"烧花鸭好吃"); appendStr(builder,"烧雏鸡好吃"); appendStr(builder,"烧子鹅好吃"); appendStr(builder,"卤猪好吃"); appendStr(builder,"卤鸭好吃"); appendStr(builder,"酱鸡好吃"); appendStr(builder,"腊肉好吃"); appendStr(builder,"松花好吃"); appendStr(builder,"小肚儿好吃"); appendStr(builder,"(-o-)结束用餐(-o-)"); appendStr(builder,getSeparator()); builder.append("</html>"); return builder.toString(); } private String getSeparator(){ return "--------------------------------------------"; } private void appendStr(StringBuilder builder,String 啊我额){ builder.append(String.format("%s <br/>",啊我额)); }} |
代码运行如下：
<ignore_js_op>
刚刚单独处理了一下分割线，那一般分割线因人而异，爱好不同，分割线样式也不同。像这种分割线有很多种样式，怎么办呢？有的同学会想到，编写接口，提供多个实现类。对，大致思路是这样，还有一个细节同学们没想到，就是最终需要做一个决策，到底使用哪种分割线样式。这个决策，我们让controller自己来确定。
V2版本
[Java] 纯文本查看 复制代码
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package com.gavin.controller;import com.gavin.common.SeparatorContext;import com.gavin.service.GenSeparator;import com.gavin.service.impl.BoLangXianSeparator;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RestController;import javax.annotation.Resource;/*** Created by 传智播客.黑马程序员.太原校区.苗雄 on 2019\8\30*/@RestControllerpublic class DemoV2Controller { @Autowired private SeparatorContext separatorContext; @Resource private GenSeparator boLangXianSeparator; @Resource private GenSeparator greaterThanSeparator; @Resource private GenSeparator hengGangSeparator; @GetMapping("/v2/lunch") public String haveLunch(){ StringBuilder builder = new StringBuilder(); builder.append("<html>"); //排队 appendStr(builder,getSeparator()); appendStr(builder,"(^o^)开始排队(^o^)"); appendStr(builder,"1只羊"); appendStr(builder,"2只羊"); appendStr(builder,"3只羊"); appendStr(builder,"4只羊"); appendStr(builder,"5只羊"); appendStr(builder,"6只羊"); appendStr(builder,"7只羊"); appendStr(builder,"8只羊"); appendStr(builder,"9只羊"); appendStr(builder,"(-o-)结束排队(-o-)"); //点菜 appendStr(builder,getSeparator()); appendStr(builder,"(^o^)开始点菜(^o^)"); appendStr(builder,"蒸羊羔"); appendStr(builder,"蒸熊掌"); appendStr(builder,"蒸鹿尾儿"); appendStr(builder,"烧花鸭"); appendStr(builder,"烧雏鸡"); appendStr(builder,"烧子鹅"); appendStr(builder,"卤猪"); appendStr(builder,"卤鸭"); appendStr(builder,"酱鸡"); appendStr(builder,"腊肉"); appendStr(builder,"松花"); appendStr(builder,"小肚儿"); appendStr(builder,"(-o-)结束点菜(-o-)"); //取餐 appendStr(builder,getSeparator()); appendStr(builder,"(^o^)开始取餐(^o^)"); appendStr(builder,"一盘蒸羊羔"); appendStr(builder,"一盘蒸熊掌"); appendStr(builder,"一盘蒸鹿尾儿"); appendStr(builder,"一盘烧花鸭"); appendStr(builder,"一盘烧雏鸡"); appendStr(builder,"一盘烧子鹅"); appendStr(builder,"一盘卤猪"); appendStr(builder,"一盘卤鸭"); appendStr(builder,"一盘酱鸡"); appendStr(builder,"一盘腊肉"); appendStr(builder,"一盘松花"); appendStr(builder,"一盘小肚儿"); appendStr(builder,"(-o-)结束取餐(-o-)"); //用餐 appendStr(builder,getSeparator()); appendStr(builder,"(^o^)开始用餐(^o^)"); appendStr(builder,"蒸羊羔好吃"); appendStr(builder,"蒸熊掌好吃"); appendStr(builder,"蒸鹿尾儿好吃"); appendStr(builder,"烧花鸭好吃"); appendStr(builder,"烧雏鸡好吃"); appendStr(builder,"烧子鹅好吃"); appendStr(builder,"卤猪好吃"); appendStr(builder,"卤鸭好吃"); appendStr(builder,"酱鸡好吃"); appendStr(builder,"腊肉好吃"); appendStr(builder,"松花好吃"); appendStr(builder,"小肚儿好吃"); appendStr(builder,"(-o-)结束用餐(-o-)"); appendStr(builder,getSeparator()); builder.append("</html>"); return builder.toString(); } private String getSeparator(){ //return separatorContext.getSeparator(boLangXianSeparator); //return separatorContext.getSeparator(hengGangSeparator); return separatorContext.getSeparator(greaterThanSeparator); } private void appendStr(StringBuilder builder,String 啊我额){ builder.append(String.format("%s <br/>",啊我额)); }} |
代码运行如下：
<ignore_js_op>
前3个版本我们只是处理了一下整个吃饭过程中的小细节。
真正的吃饭过程的代码还是很长的，得翻好多屏，并且排队、点菜、取餐、用餐，4块逻辑，顺序执行，单独某一块比较独立。另一个是，没使用上MVC分层思想，应该将业务代码放到业务层中。这样controller中的代码就很少了。业务层，我们也可以按业务功能细分一下，针对controller中出现的4块逻辑，各自创建一个Service类。这样就完美的解决了MVC问题与代码长的问题了。
最后一个问题，字符串处理属于公共逻辑，可以把它抽取到一个StringUtil的公共类中，供Controller和Service调用。
V3版本
[Java] 纯文本查看 复制代码
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package com.gavin.controller;import com.gavin.common.SeparatorContext;import com.gavin.common.StringUtil;import com.gavin.service.*;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RestController;import javax.annotation.Resource;/*** Created by 传智播客.黑马程序员.太原校区.苗雄 on 2019\8\30*/@RestControllerpublic class DemoV3Controller { @Autowired private SeparatorContext separatorContext; @Resource private GenSeparator boLangXianSeparator; @Resource private GenSeparator greaterThanSeparator; @Resource private GenSeparator hengGangSeparator; @Autowired private OrderService orderService; @Autowired private QueueService queueService; @Autowired private TakeFoodService takeFoodService; @Autowired private HaveDinnerService haveDinnerService; @GetMapping("/v3/lunch") public String haveLunch(){ StringBuilder builder = new StringBuilder(); builder.append("<html>"); StringUtil.appendStr(builder,getSeparator()); StringUtil.appendStr(builder,queueService.execute()); StringUtil.appendStr(builder,getSeparator()); StringUtil.appendStr(builder,orderService.execute()); StringUtil.appendStr(builder,getSeparator()); StringUtil.appendStr(builder,takeFoodService.execute()); StringUtil.appendStr(builder,getSeparator()); StringUtil.appendStr(builder,haveDinnerService.execute()); StringUtil.appendStr(builder,getSeparator()); builder.append("</html>"); return builder.toString(); } private String getSeparator(){ //return separatorContext.getSeparator(boLangXianSeparator); //return separatorContext.getSeparator(hengGangSeparator); return separatorContext.getSeparator(greaterThanSeparator); }} |
代码运行如下：
<ignore_js_op>
从这4个版本中可以感受到，出现拼拼凑凑的感觉时，那么你的代码就是内聚性比较低的表现了。如果代码总要变来变去，其实是耦合高的表现。
最后，想要提高内聚性，可以通过降低耦合度来达到目的。在这儿，我个人提倡同学们编写高内聚、低耦合的代码。
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