Java Best Practices

Best practices in Coding, Designing and Architecting Java Applications

Coding

###How to become a good programmer?

###Ask Why?

Ask Why?

Should I be an expert at all Design Patterns?

My personal view : Design Patterns are good to know. Have a good idea on what each one of them does. But, that where it ends. I’m not a big fan of understanding the intricate details of each Design Pattern. You can look it up if you have a good overall idea about Design Patterns.
Full Video on Design Patterns : https://www.youtube.com/watch?v=f5Rzr5mVNbY
Java EE Design Patterns : https://github.com/in28minutes/Java-EE-Design-Patterns/blob/master/JavaEE%20Design%20Patterns%20and%20Architecture%20-%20Presentation%20v0.7.pdf
Java Design Patterns : https://github.com/in28minutes/Design-Patterns-For-Beginners/blob/master/DesignPatterns-Presentation.pdf

What is TDD?

What is BDD?

What is ATDD?

What are NFRs?

What is Sonar?

Do not be fooled by Code Coverage?

How can you increase performance and reliability of applications using Queues?

What are the most important coding standards?

Complexity of a method
Naming variables, methods and classes
Size of methods and classes
Number of parameters

Why is unit testing important?

Why should a good programmer understand Mocking?

Why is it important to have an API Standard?

YARAS

Why should you create a reference component?

What is the importance of Logging and Centralized Monitoring?

What happens behind Maven? What is a Repository?

Automate! Automate! Automate!

Why is it important?
Personal Experience with Deployment Automation, Providing user screen with requests/responses

When should you have multiple CI builds?

Why is performance of Unit Tests important?

What are Cloud Native Applications?

What are micro-services?

Why should you avoid floats for Calculations?

Why is it important to use Continuous Integration from Day 0 of the project?

What is a vertical slice? Why should you need it?

What is defensive programming?

Why should you have minimum scope for variables?

Why should you understand performance of String Concatenation?

Why should you optimize judiciously?

What are the best practices with Exception Handling?

When is it recommended to prefer Unchecked Exceptions?

Spring Framework

When do you use a Marker Interface?

Why are ENUMS important for Readable Code?

Why should you minimize mutability?

What is functional programming?

Why should you prefer Builder Pattern to build complex objects?

Why should you build the riskiest high priority features first?

Why should you have api & impl in each layer maven projects?

Why should you create small components?

Why should you have coding standards?

Why should you migrate to GIT?

What are the 4 Principles of Simple Design?

What is Pair Programming?

Whatt are Best Practices of Distribute Agile?

Why is readable code important?

What is component based architecture?

Why should you commit your code often?

What is use of Maven Parent POM?

Why should you write unit tests with/before code?

What are version control best practices

Do not commit derived files.
Do not commit IDE files.
Commit often
Use Git

A few design patterns...

Why do Stateless applications perform better?

###Code Quality Overview

More than everything else, code quality is an attitude. Either, the team has it or not. The attitude to refactor when something is wrong. The attitude to be a boy scout. As an architect, it is important to create an environment where such an attitude is appreciated. (There are always bad sheep, who take the code quality to such depth that it is not fun anymore, but I like them more than developers who keep churning out bad code).
Have a good static analysis tool(and is part of Continuous Integration). Sonar is the best bet today. Understand the limits of Static Analysis. Static Analysis is not a magic wand. For me, results from Static Analysis are a signal: It helps me decide where I should look during peer or architect reviews?
Have good peer review practices in place. Every user story has to be peer reviewed. Put more focus on peer reviews when there is a new developer or there is a new technical change being done. Make best use of Pair Programming. The debate is ongoing : Is pair programming more productive or not? I would rather stay out of it. You make your choice. However, these two scenarios are bare minimum:
Onboarding a new programmer. Makes him comfortable with all the new things he has to encounter.
Implementing a complex functionality.
Next question is how to approach a Code Review. Difficult to cover everything. I would make a start. When doing a code review, I start with static analysis results (for example, sonar). I spend 10 minutes getting an overview of components and/or layers (focusing on size and dependencies). Next I would pick up a unit test for a complex functionality. I feel unit tests are the best place to discover the dependencies and naming practices (I believe good names = 50% of maintainable code). If a programmer can write a simple and understandable unit test, he can definitely write good code. Next, I look for 4 principles of Simple Design. After this, there are 100 other things we can look for - You decide.

Why should you not take code quality tools at face value?

If a project has a great Sonar report, does it mean it is perfect?
Nope, code quality tools are just a guidance!
Your focus should be to write code that adheres to "4 Principles of Simple Design"
Peer Reviews are necessary!

Security

Hmmm... Should I really explain the importance of Security? Presentation : https://github.com/in28minutes/java-best-practices/blob/master/pdf/SecuringYourApplication-OWASP.pdf

Performance

First and Foremost - NO premature optimizations. Any optimization decision should be based on numbers or past experience. In Donald Knuth's paper "Structured Programming With GoTo Statements", he wrote: "Programmers waste enormous amounts of time thinking about, or worrying about, the speed of non critical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%."
Session size - Small
Implement Caching whereever possible
Set initial size on Collections
Create necessary Indexes on Database. Collect Statistics and Remove unnecessary data
In critical parts - write unit tests for performance.
Be conscious about create as few objects as possible. Especially in loops.
Avoid String Concatenation
Close connections and Streams

Load and Performance Testing

PDF Presentation https://github.com/in28minutes/java-best-practices/blob/master/pdf/LoadAndPerformanceTestingBestPractices.pdf
Have clear performance objectives. That’s the single most important objective. Decide Peak Load, Expected Response Time, Availability Required before hand.
Establish clear performance expectations with the Interface Services
An application does not work on its own. It connects with a number of external interfaces. Establish clear performance expectations with the Interface Services
The next important thing is to ensure that you mirror your production environment. A load testing environment should be the same as your production environment. We will discuss the exact factors involved later in this article.
Validate early : Do performance testing as early as possible.
Make it a regular practice to use profilers in development environment. ex:JProfiler
Make sure team is not making premature optimizations. Any optimization decision should be based on numbers or past experience. In Donald Knuth's paper "Structured Programming With GoTo Statements", he wrote: "Programmers waste enormous amounts of time thinking about, or worrying about, the speed of non critical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%."
Have Clear Strategy on How to Handle expected load. What would be the initial settings on the application server? Do you plan to use a clustered environment? Do you need a load balancer?

Design

###Design Focus Areas

4 Principles of Simple Design. https://www.youtube.com/watch?v=OwS8ydVTx1c&list=PL066F8F24976D837C
Runs all tests
Minimize Duplication
Maximize Clarity
Keep it Small
Object Oriented Programming. Have good object, which have well-defined responsibilities. Following are the important concepts you need to have a good overview of. These are covered in various parts in the video https://www.youtube.com/watch?v=0xcgzUdTO5M. Also, look up the specific videos for each topic.
Coupling :
Cohesion : https://www.youtube.com/watch?v=BkcQWoF5124&list=PLBBog2r6uMCTJ5JLyOySaOTrYdpWq48vK&index=9
Encapsulation
Polymorphism : https://www.youtube.com/watch?v=t8PTatUXtpI&list=PL91AF2D4024AA59AF&index=5
SOLID Principles : https://github.com/in28minutes/java-best-practices/blob/master/pdf/SOLIDPrinciples.pdf
UML is next even though, formal use of UML is on the way down with Agile. However, I think UML is a great tool in the arsenal for a white board discussion on design. A picture is worth thousand words. I recommend having a good overview of the UML basics. Focus on these four before you move on to others.
Class diagrams
Sequence diagrams
Component diagrams
Deployment diagrams
Design Patterns. Following video covers all the major design patterns. https://www.youtube.com/watch?v=0jjNjXcYmAU. My personal view : Design Patterns are good to know. Have a good idea on what each one of them does. But, that where it ends. I’m not a big fan of understanding the intricate details of each Design Pattern. You can look it up if you have a good overall idea about Design Patterns. https://github.com/in28minutes/java-best-practices/blob/master/pdf/DesignPatternsForBeginners.pdf https://github.com/in28minutes/java-best-practices/blob/master/pdf/J2EE(Java%20EE)%20Design%20Patterns%20and%20Architecture.pdf

###Design Review

Architecture

PDF - How to be a good architect : https://github.com/in28minutes/java-best-practices/blob/master/pdf/How%20to%20be%20a%20good%20Software%20Architect.pdf

Architect Responsibilities

Having good governance in place. Good review processes in place for Architecture, Design and Code.
Creating a clean architecture based on sound principles. Architecture covering all Non Functional Requirements.
Ensuring teams are as productive as they can be. Right tools.
Ensuring teams are following the best engineering practices.
Ensuring clear communication about architecture with business and technical teams.

Architect Qualities

Most important qualities I look for in an Architect are

Impeccable Credibility : Somebody the team looks up to and aspires to be.
Super diagnostic skills : The ability to do a deep dive on a technology issue. When developers are struggling with a problem (having tried different things), Can he/she provide a fresh pair of eyes to look at the same problem?
Forward Thinker and Proactive : Never satisfied with where we are. Identifies opportunities to add value fast.
Great Communication : Communication in the widest sense. Communicating the technical aspects to the stakeholders, project management, software developers, testers, etc.

###Architecture Review

SOAP Web Services

REST Web Services

PDF TO UPDATE https://www.mindmup.com/#m:g10B8KENIDghuHAYmFzM0daOU80SDA

How should you document your REST Web Services?

Swagger

Distributed Cache

Layers

PDF https://github.com/in28minutes/java-best-practices/blob/master/pdf/LayeringInJavaApplications.pdf

Business Layer

Listed below are some of the important considerations

Should I have a Service layer acting as a facade to the Business Layer?
How do I implement Transaction Management? JTA or Spring based Transactions or Container Managed Transactions? What would mark the boundary of transactions. Would it be service facade method call?
Can (Should) I separate any of the Business Logic into seperate component or service?
Do I use a Domain Object Model?
Do I need caching? If so, at what level?
Does service layer need to handle all exceptions? Or shall we leave it to the web layer?
Are there any Operations specific logging or auditing that is needed?Can we implement it as a cross cutting concern using AOP?
Do we need to validate the data that is coming into the Business Layer? Or is the validation done by the web layer sufficient?

Data Layer

Do we want to use a JPA based object mapping framework (Hibernate) or query based mapping framework (iBatis) or simple Spring DO?
How do we communicate with external systems? Web services or JMS? If web services, then how do we handle object xml mapping? JAXB or XMLBeans?
How do you handle connections to Database? These days, its an easy answer : leave it to the application server configuration of Data Source.
What are the kinos of exceptions that you want to throw to Business Layer? Should they be checked exceptions or unchecked exceptions?
Ensure that Performance and Scalability is taken care of in all the decisions you make.

Web Layer

First question is do we want to use a modern front end javascript framework like AngularJS? If the answer is yes, most of this discussion does not apply. If the answer is no, then proceed?
Should we use a MVC framework like Spring MVC,Struts or should we go for a Java based framework like Wicket or Vaadin?
What should be the view technology? JSP, JSF or Template Based (Velocity, Freemarker)?
Do you want AJAX functionality?
How do you map view objects to business objects and vice-versa? Do you want to have View Assemblers and Business Assemblers?
What kind of data is allowed to be put in user session? Do we need additional control mechanisms to ensure session size is small as possible?
How do we Authenticate and Authorize users? Do we need to integrated external frameworks like Spring Security?
Do we need to expose external web services?

Tools

Maven Best Practices

10 Tips For Maven

10 Tips for Eclipse and Maven

IDE - Eclipse

10 Tips For Eclipse