Software Architecture - Why do we use Layered Architectures?

In this article, we explore the reasons why we build applications with several layers. We also look at different options for each layer in the Java world.

You will Learn

  • Why Have Multiple Layers?
  • What are typical layers and their responsiblities?
  • What are the typical frameworks used in each layer in the Java world?

This is the fifth article in the following series of articles on Software Architecture :

Why Have Multiple Layers?

When we build any large application, such as a web application or service, we try to organize it into multiple layers. We could go for layers such as Web, Business, Access, among others:

image info

The reason we go to such lengths is a very important underlying principle : separation of concerns.

Each of the layers above have different responsibilities. Web layer is responsible for presenting information to the user. The Business layer is responsible for application’s business logic. The Data layer is responsible for taking care of the data access, and configuring and talking to the data stores. You might also have an additional access layer to talk to external applications, or queueing messages for dispatch.

By defining each layer to have a separate responsibility, you ensure high cohesion with-in each such layer.

Layers In Enterprise Java

When it comes to the Java world, the typical organization of enterprise applications follows this schematic:

image info

Implementing The Web Layer

Earlier, the web layer of a Java EE application is responsible for rendering the final view to the user with technologies like JSPs and variety of templating languages. With the advent of RESTful web services and evolution of JavaScript SPA frameworks, this has changed drastically.

Today, we expose a REST API from the Java Web layer, and a front-end framework (such as AngularJS or ReactJS) handles the user presentation.

The main responsibility of a web layer is to talk to business layer and send a proper response to REST API calls.

Another responsibility that a web layer typically handles is authentication and authorizations using a module like Spring Security.

image info

A few important decisions when designing your web layer are

  • Should the application have state? If yes, you need to store session information about the user. Ideally, you should not.
  • Which framework to use? The popular options are Spring Boot (MVC), JAX-RS(REST), JAX-WS(SOAP).

Implementing The Business Layer

image info

Lets look at the important business layer responsibilities:

Transaction Management

This is taken care of by Java Transaction API (JTA) and Spring Transactions.

Implementing The Access Layer

image info

The following are the responsibilities of the Access layer:

Communicating with Data Store

If your application communicates with an external database, JPA might be a good choice. If very complex database queries are needed, then you might want to use JDBC or MyBatis.

Spring Data JPA might be a good starting point for using JPA and Hibernate.

Communication With External Interfaces

This layer provides interface with the JMS module. It also communicates with AMQP implementations.

Other Layers

image info

One of the most important aspects that needs to be handled in any system is Cross Cutting Concerns. This includes tasks such as logging, performance and security.

Typically these are implemented using Aspect Oriented Programming. AspectJ and Spring AOP are options to consider.

Unit Testing

Unit testing of the application is another important concern. Typical frameworks that are provided include JUnit, Mockito and Spring Unit.

Do check out our video on this:

image info


In this article, we understood why we need to have multiple layers in an application. We looked at the layers in a typical Java web application, along with framework options available. We then had a look at the makeup of the individual Data, Business and Access layers of a typical Java web application.

10 Step Quick Introductions to Frameworks

Image Image Image Image Image

in28Minutes is helping 300,000 Learners across the world reach their learning goals. Click here for the complete catalogue of 30 Courses.

Related Posts

Spring Boot Tutorials for Beginners

At in28Minutes, we are creating a number of tutorials with videos, articles & courses on Spring Boot for Beginners and Experienced Developers. This resources will help you learn and gain expertise at Spring Boot.

Spring and Spring Boot Video Tutorials for Beginners

At in28Minutes, we are creating a number of tutorials with videos, articles & courses on Spring Boot for Beginners and Experienced Developers. Here's a list of video tutorials and courses for you

Software Design - Separation Of Concerns - with examples

Software architects and programmers love having Seperation of Concerns. What is it? Why is it important? Let's get started.

Object Oriented Software Design - Solid Principles - with examples

Software design is typically complex. Object oriented design takes it to the next level. There are a number of design patterns and other stuff to be aware of. Can we make things simple? What are the goals to aim for when you are doing object oriented design? SOLID Principles is a great starting point for Object Oriented Design.

Software Design - Open Closed Principle - with examples

Open Closed Principle is one of the SOLID Principles. You want your code to be easily extended. How do you achieve it with minimum fuss? Let's get started.

Software Design - What is Dependency Inversion Principle?

Dependency Inversion Principle is one of the important SOLID Principles. Dependency Inversion Principle is implemented by one of the most popular Java frameworks - Spring. What is it all about? How does it help you design good applications?

Introduction to Four Principles Of Simple Design

With agile and extreme programming, the focus is on keeping your design simple. How do you keep your design simple? How do you decide whether your code is good enough?

Software Design - Single Responsibility Principle - with examples

For me, Single Responsibility Principle is the most important design principle. What is Single Responsibility Principle? How do you use it? How does it help with making your software better? Let's get started.

REST API Best Practices - With Design Examples from Java and Spring Web Services

Designing Great REST API is important to have great microservices. How do you design your REST API? What are the best practices?

Designing REST API - What is Code First Approach?

Designing Great REST API is important to have great microservices. Code First approach focuses on generating the contract from code. Is it the best possible approach?