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 {

background-color: blueviolet;

}

</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：
编码至高法则-高内聚低耦合
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：
编码至高法则-高内聚低耦合 
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
 

[JavaScript] 纯文本查看 复制代码

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h1 {

    background-color: blueviolet;

}


gnj_v2.html

[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>

    <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

*/

@RestController

public 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：

编码至高法则-高内聚低耦合 

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

*/

@RestController

public 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：
编码至高法则-高内聚低耦合 

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

*/

@RestController

public 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：
编码至高法则-高内聚低耦合 


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

*/

@RestController

public 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：
编码至高法则-高内聚低耦合 

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。

编码至高法则-高内聚低耦合

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