Fear of reconstruction? I'm too late to tell you how to refactor. Now I'm here

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A few days ago, I happened to see the content of an online friend , It's said that the old system crashed after changing a line of code , It's really bald . The more successful the company is , The more old systems and legacy code that can't be counted , In particular, code related to basic services , It's a real-life version of a gourd that floats . Start up companies are better , There is no burden of history . We also often refactor old code , If for no other , It's just that I'm afraid it's moldy for too long . It happens that I'm also doing system refactoring recently , Sum up what we're doing and some tips .

Code can get moldy, too

It's not just food that molds , The code will also . We usually call it corruption . The process of corruption happens every day , An urgent need , A new colleague joins in , A perverted problem fix , A co construction project , wait . corrupt , It can never be avoided , Just like the entropy of the universe is irreversible . In the face of corruption , Architects often add a coating . If your system doesn't have an anti-corrosion coating , Think about it now . Even if there's an anti-corrosion coating , Also can not withstand the devastation of the years , It's like hair's thinning out , That's life .

therefore , We need to refactor . It takes a lot of work to reverse entropy , To sort out the messy code again , Make it clear again 、 A state of well-defined architecture .

carding , Or comb

Spend a lot of time sorting out the historical logic before reconstruction , And be careful . The ancients said “ A good workman does his work well , You must sharpen your tools first ”. The logic sorted out is the guiding light of reconstruction . What to discard , What needs to be optimized , What to refactor , Which products need to be repositioned , What are the risk points , After carding, it is basically clear that . It's not just the emergence of logic that brings about , There may also be the direction of Architecture . By combing , Be able to clearly discover business logic , You can even define new domain models 、 value 、 Events, etc. . Think of the Galactic era , Fight with the real-time star map of the galaxy , You know how important it is to comb .

The playback , Contrast changes

After refactoring , The test should cover all aspects of . Now , Playback is very important . Ali also open source a playback tool jvm-sandbox-repeater.GitHub Address https://github.com/alibaba/jvm-sandbox-repeater. Through playback , It can be in the pre launch environment debug Online problem , You can see the actual performance of online real traffic in the pre launch environment . by force of contrast , You can find out what's different after refactoring , In particular, page rendering and persistent data .

After the playback is finished , It can also be used as a quick verification of daily releases . As long as there is no difference between this playback and the last normal playback , Basically, the risk is very small .

framework , Start with the end

Now that we're doing refactoring , In terms of architecture, we should design well . Try to get rid of the intricate historical logic , Design a new architecture . To improve R & D efficiency 、 Reducing maintenance costs is the ultimate goal , All of the refactoring design revolves around this goal . Nothing can't be changed , If not , Then add two better programmers . If the refactoring keeps a pile of shitty legacy code , I don't know the meaning of refactoring . Refactoring is about starting with the end , In the new architecture design , Let legacy code be reincarnated to get new life .

improve , Code refactoring

Good programmers need to refactor existing code more or less from time to time . stay 《 restructure Improve the design of existing code 》 In a Book , The author has given many concrete methods of refactoring . Duplicate code extraction 、 Too long function split 、 Model redesign 、 Encapsulate fields 、 Encapsulation set 、 With State/Strategy Replace type code 、 Methods moving position and many other skills , It's not going to unfold here . I think every programmer should study this book well , And then go deep into code level refactoring . As the book review said “ You shouldn't go through the refactoring manual , But it's important to know what's mentioned in this book 70 There are several reconstruction methods in mind ”.

Speed , A quick victory

A lot of legacy code is already like online loan , Deeper and deeper . The return on the resources invested , It's actually much higher than maintaining old code . The process of refactoring should be fast , During the process, daily needs should be suspended as much as possible . Refactoring is a lot of work , But it's also very fast . If you reconstruct , One side of the line is still changing requirements , It's likely to get into trouble , Even lost online logic after refactoring . It's done , The playback is done , Programmers can quickly refactor as planned , A few more people , Make sure it's done quickly .

State of mind , Calibrated boldness

All the work ahead has been done , Then the next step is to do .

Don't worry about it , Don't particularly . This code does not understand how to do , Change ！ Watch the replay . This code is stinky and hard , Change ！ Watch the replay .

When we change it , Be careful, too , Understand the original business logic . Defy the enemy strategically , We should also attach importance to the enemy tactically . do code review, Let the people who know see the changes together , Or team members to check the gate together .

So , I'd like to recommend this book ---《 restructure 》, I'd like to share it with you

Adapt to people

The target audience of this book is Professional programmers , Those who write software for a living . Examples and discussions in the book , It involves a lot of code that needs to be read and understood in detail . These examples are all in the form of Java It's written in . The reason for choosing Java, Because it's a language that is more and more widely used , and Anything with C Language background People can easily understand it .Java Is an object-oriented language , The object-oriented mechanism is very helpful for refactoring .

Although the focus is on Code , but Refactoring for system design It also has a huge impact . It's also important for senior designers and architects to understand the principles of refactoring , And use refactoring technology in your own projects . It's better to have seniority 、 Experienced developers introduce refactoring techniques , Because such people are the best at understanding the principles behind refactoring , And adjust it according to the situation , Apply it to a specific area of work . If you don't use Java, This is especially important , Because you have to rewrite my example in other languages .

Now I want to tell you , How to make full use of it without reading the whole book .

If you want to know why you should refactor , Please read the first two chapters . They tell you what refactoring is and why it should be refactored .

The first 1 Chapter reconstruction , The first case

The first 2 Chapter reconstruction principle

If you want to know where to refactor , Please read before 5 Chapter . It will tell you some code features , These characteristics point to “ We need to refactor ”.

The first 3 Bad smell of chapter code

The first 4 Chapter 2 constructs the test system

The first 5 Chapter refactoring list

The first 6 Chapter reorganizing functions

The first 7 Chapter moves features between objects

The first 8 Chapter reorganizing the data

The first 9 In this chapter, we simplify the conditional expression

The first 10 Chapter simplifying function calls

The first 11 Chapter deals with general relations

The first 12 Chapter large reconstruction

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If you want to start refactoring , From 5 The chapter extends to 12 Chapter . It can't be said to be a comprehensive list , It's just a start , It includes all the refactoring techniques I've sorted out in my work so far . I hope this is a part that you should review again and again in the future . Just skim the list at first , Look at some of them , You don't have to understand all the details . Once there is a real need to implement a code , Read it in more detail , Get help from . The list section is for reference , You don't have to read it all at once .

In addition, you should also read the list of other authors “ Guest section ”, Especially in the first 15 Chapter .

The first 13 Chapter reconstruction , Reuse and reality

The first 14 Chapter refactoring tool

The first 15 Chapter summary

So-called ** restructure （refactoring)** It's a process like this : Without changing the external behavior of the code , Make changes to the code , To improve the internal structure of the program . Refactoring is a methodical method of program arrangement which has been formed through a lot of efforts , It can minimize the possibility of introducing errors in the finishing process . In essence , Refactoring is to improve the design of the code after it is written .

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