All excerpts from This is How Design Patterns should Be Learned
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The preface
Design Patterns: Elements of Reusable Object-oriented Software (Design Patterns), It is written by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides (Addison-Wesley, 1995). These Four authors are often referred to as the Gang of Four, and this book is known as the GoF book. For the first time, they gave us a set of experiences that can be used repeatedly in software development, helping us improve the reusability of code, the maintainability of system, etc., and solving complex problems in software development.
Design patterns have been in existence for more than 20 years, during which numerous classic works on design patterns have been published. If GoF’s Design Patterns is the “Bible” in the field of design patterns, then the various subsequent books on design patterns can be called “annotated editions” or “vernacular editions” of the bible. This book is based on GoF’s Design Patterns.
Design Patterns is a book of lessons. Don’t memorize them. Here’s a general preview of the classification and summary of design patterns, as shown in the table below.
| Divide class | explanation | For example |
|---|---|---|
| Creational Design Patterns | This type of design pattern provides a way to hide the creation logic while creating objects, rather than instantiating them directly with new operators, giving programs more flexibility in deciding which objects to create for a given instance | Factory Method Pattern,Abstract Factory Pattern,Singleton Pattern,Prototype Pattern,Builder Pattern |
| Structural design Pattern | This type of design pattern focuses on combinations of classes and objects. The concept of inheritance is used to combine interfaces and define how composite objects acquire new functionality | Proxy Pattern,Facade Pattern,Decorator Pattern,Flyweight Pattern,Composite Pattern,Adapter Pattern,Bridge Pattern |
| Behavioral design Patterns | This type of design pattern is particularly concerned with communication between objects | Template Method Pattern,Strategy Pattern,Chain of Responsibility PatternIterator Pattern, Command Pattern, State Pattern, Memento Pattern, Mediator Pattern Interpreter Pattern, Observer Pattern, Visitor Pattern |
This article is my “Bible” practice of the essence of the summary, the full content is excerpted from the “Design pattern should be learned”, this is a can really be ground “design pattern” book, is currently the only combination of framework source code how to ground “design pattern” this Angle to understand the design pattern book. This paper will also be combined with JDK, Spring, MyBatis, Tomcat, Netty and other classic framework source code to expand the analysis of the design pattern. , of course, this article also combined with my years of experience in “trample hole filling holes” and “answering questions of teaching experience, with more than the” bible “, more comprehensive, more popular, more lively, more interesting, more ground gas way and combining with the real business scenario analysis the advantages and disadvantages of each design pattern, cure “design mode selection difficult disease”. Choosing a design pattern is like choosing a partner on a blind date. Once you’re ready to accept their flaws, they belong to you. Therefore, this article is more instructive for daily development.
Tom plays architecture, only play dry goods without water, all the content to share in this article is from the actual combat perspective, do not talk about the concept, only about actual combat and application
Summary of frequency of use of various design modes
The following is a summary of the frequency of use of design patterns based on my personal experience, which is not academic basis but for your reference only. Because the choice of design pattern is still dependent on the specific business scenario, everyone is in contact with different business areas, the choice of natural design pattern will be different.
1.1 Creative design pattern
As shown in the figure below, the use frequency of creative design pattern from high to low is factory method pattern, abstract factory pattern, Builder pattern, singleton pattern and prototype pattern. Archetypal patterns tend to have off-the-shelf toolclasses, and it’s rare to build your own wheels.
1.2 Structural design mode
As shown in the figure below, the frequency of structural design mode is adapter mode, decorator mode, agent mode, facade mode, combination mode, share mode and bridge mode in descending order. The bridge mode generally has a ready-made tool class, the case of their own wheels is relatively rare.
1.3 Behavioral design pattern
As shown in the figure below, the frequency of use of behavioral design patterns from high to low is policy pattern, observer pattern, chain of responsibility pattern, interpreter pattern, template method pattern, iterator pattern, mediator pattern, command pattern, visitor pattern, memo pattern, and state pattern. Among them, observer mode, interpreter mode, iterator mode, mediator mode, command mode, visitor mode, memo mode generally have a ready-made tool class, the self-made wheel is relatively rare.
The following according to my years of experience in the study of design mode, will be the first time the container dry goods released throughout the network. If this article is helpful to you must collect, also welcome to pay attention to and like; If you have any suggestions can also leave a comment or private letter, your support is my motivation to adhere to the creation. Pay attention to “Tom bomb architecture” for more technical dry goods!
2. Why must we learn design patterns
| The title | note |
|---|---|
| Tom Plays architecture: Why do you have to learn design patterns | 2021/10/29 has been updated |
Seven architecture Design Principles
| The title | note |
|---|---|
| Open Closed Principle (OCP) | 2021/10/21 has been updated |
| Tom missile architecture: Dependence Inversion Principle (DIP) | 2021/10/22 has been updated |
| Tom framework: Simple Responsibility Principle (SRP) | 2021/10/23 has been updated |
| Tom Framework: Interface Segregation Principle (ISP) | 2021/10/24 has been updated |
| Tom: Law of Demeter (LoD) | 2021/10/25 has been updated |
| Tom shells: Liskov Substitution Principle (LSP) | 2021/10/26 has been updated |
| Tom Elastic Architecture: Composite/Aggregate Reuse Principle, CARP | 2021/10/27 has been updated |
The catalog only represents the update plan, and may not be serialized in sequence due to the allocation of energy. The serialization will be completed within one month (i.e., before November 31, 2021). Please pay attention to the update of this article.
4. Creative design patterns
| The title | note |
|---|---|
| Tom plays architecture: Simple Factory Pattern (Simple Factory Pattern) >> Thoroughly explain Simple Factory details that you haven’t paid attention to | 2021/11/10 has been updated |
| Tom play architecture: Factory Method Pattern >> fully transparent in-depth analysis of Factory Method Pattern | 2011/11/11 has been updated |
| Abstract Factory Pattern >> Handwritten database connection pool, so that the Abstract Factory is no longer Abstract | 2021/11/12 has been updated |
| How many of the 9 destroyed Singleton patterns have you encountered? | 2021/10/26 has been updated |
| Tom play architecture: Prototype Pattern >> article to understand the relationship between deep cloning and shallow cloning | 2021/11/01 has been updated |
| Using the Builder Pattern to implement an ORM framework against SQL injection | 2021/10/26 has been updated |
5. Structural design mode
| The title | note |
|---|---|
| No one has ever analyzed Proxy Pattern so thoroughly | 2021/10/27 has been updated |
| Tom plays architecture: Facade Pattern >> You don’t know you use Facade Pattern every day | 2021/11/13 has been updated |
| Interesting talk about Decorator patterns that you will never forget | 2021/11/01 has been updated |
| Flyweight Pattern = Flyweight Pattern = Flyweight Pattern = Flyweight Pattern = Flyweight Pattern = Flyweight Pattern | 2021/11/01 has been updated |
| # Infinite level menu trees with no performance bottlenecks should be designed like this | 2021/11/04 has been updated |
| >> # How to quickly handle third-party login and easy to expand? | 2021/11/03 has been updated |
| Use Bridge patterns to design complex messaging systems | 2021/11/08 has been updated |
Behavioral design patterns
| The title | note |
|---|---|
| You think the Delegate Pattern is mysterious, but you use it every day | 2021/11/09 has been updated |
| Tom plays the framework: Template Method Pattern (Template Method Pattern) >> understand the hook Method and Template Method, read this article is enough | 2021/11/07 has been updated |
| Tom shell architecture: Strategy Pattern >> Using Strategy Pattern to reconstruct e-commerce discount and payment scenarios | 2021/11/05 has been updated |
| This is an elegant use of the Chain of Responsibility Pattern | 2021/10/27 has been updated |
| Iterator Pattern: Iterator Pattern | To be updated… |
| Tom shell architecture: Command Pattern | To be updated… |
| Tom shell architecture: State Pattern | To be updated… |
| Tom: Memento Pattern | To be updated… |
| Mediator Pattern: Mediator Pattern | To be updated… |
| Tom shells: Interpreter Pattern | To be updated… |
| Tom shell architecture: Observer Pattern | To be updated… |
| Tom structure: Visitor Pattern | To be updated… |
New design patterns
| The title | note |
|---|---|
| Object Pool Pattern | To be updated… |
| Specification Pattern of Tom shells | To be updated… |
| Tom shell architecture: Null Object Pattern | To be updated… |
| Tom: Employee Pattern | To be updated… |
8. Summarize design patterns in one sentence
The comparison of various design modes and the summary of programming ideas are shown in the following table.
| Design patterns | Sum up in one sentence | The eye of | Life case | Framework source code examples |
|---|---|---|---|---|
| Factory Pattern | Product standardization, More efficient production |
Package creation details | Physical plant | LoggerFactory, Calender |
| Singleton Pattern | There is only one me | Guarantee uniqueness | CEO | The BeanFactory, Runtime |
| Prototype Pattern | Pull out a monkey’s hair, Blow out thousands |
Creating objects efficiently | cloning | ArrayList, PrototypeBean |
| Builder Pattern | High matching medium matching and low matching, You can go with whatever you want |
Open the personality configuration step | optional | The StringBuilder, BeanDefinitionBuilder |
| Proxy Pattern | No resources, no time, We need a matchmaker to help us |
Strengthen the responsibility | matchmaker | ProxyFactoryBean, JdkDynamicAopProxy, CglibAopProxy |
| Facade Pattern | Open a door, To the world |
Unified access portal | The front desk | JdbcUtils, RequestFacade |
| Decorator Pattern | His great uncle, his second uncle, Is his uncle |
Flexible expansion, Of the same |
pancakes | BufferedReader, InputStream |
| Flyweight Pattern | Optimize resource allocation, Reduce duplication and waste |
Shared Resource Pool | National Social Security Network | String, Integer, ObjectPool |
| Composite Pattern | People in groups are called gangs, Hearts together make a team |
Unify the whole and the individual | Organization structure tree | A HashMap, SqlNode |
| Adapter Pattern | Universal charger | Compatible with conversion power adaption | AdvisorAdapter, HandlerAdapter | |
| Bridge Pattern | Convention over Configuration | Inheritance is not allowed | The bridge | DriverManager |
| Delegate Pattern | The requirement is simple, I don’t care how |
Only responsible for results | Power of attorney | This, BeanDefinitionParserDelegate |
| Template Pattern | All processes are standardized, Need fine tuning please overwrite |
Logic reuse | Put the elephant in the fridge | JdbcTemplate, HttpServlet |
| Strategy Pattern | All roads lead to Beijing. Which one is up to you |
Give the choice to the user | Choose payment method | The Comparator, InstantiationStrategy |
| Chain of Responsibility Pattern | Each man sweeps the snow from his own door, Never mind the frost on another’s tile |
Decouple processing logic | The buck | FilterChain, Pipeline |
| Iterator Pattern | Sitting on an assembly line all day, Scan each package once |
Unify access to collections | Check in one by one | Iterator |
| Command Pattern | Strategizing, A victory thousands of miles away |
Decouple requests and processing | The remote control | A Runnable, TestCase |
| State Pattern | State-driven behavior, Behavior-determined state |
Bind state and behavior | Order status tracking | Lifecycle |
| Memento Pattern | If I stumble, I’ll be damned. Start over if you want to |
Backup, regret mechanism | Draft box | StateManageableMessageContext |
| Mediator Pattern | I’ll give you the contact information, How do I care |
Manage network resources in a unified manner | Circle of friends | Timer |
| The Interpreter Pattern | I want to speak dialect, All interpretation is my prerogative |
Implement specific syntax parsing | Morse code | The Pattern, ExpressionParser |
| Observer Pattern | Let me know when it arrives | Decouple the observer from the observed | The alarm clock | ContextLoaderListener |
| Visitor Pattern | Viewed horizontally as a ridge forming a peak on its side, Near, far, high and low |
Decouple data structures and data operations | The KPI assessment | FileVisitor, BeanDefinitionVisitor |
There are also numerous UML diagrams and confusing design pattern comparison case studies in This is How Design Patterns should Be Learned.
In everyday use, design patterns are never used independently of one another. In practice, multiple design patterns are often used in a mix, where you are part of me and I am part of you. The following diagram completely describes the mixed relationships between design patterns, which I hope will be helpful.
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