编码至高法则- 高内聚低耦合

v587博客 2021-08-24

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编码至高法则

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

<!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，好比在一个大开间里做饭、吃饭、睡觉、洗漱等等。

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

document.write("高内聚低耦合 demo");

h1.css

h1 {
background-color: blueviolet;
}

gnj_v2.html

<!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

package com.gavin.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* Created by 海文
*/
@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：

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

package com.gavin.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* Created by 海文 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：

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

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 海文 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：

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

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 海文 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);
}
}