Three-Layer Architecture Used in Software Development
Tags: webdev, programming, javascript, softwarearchitectures
Published: 2023-04-17 23:13:55

A typical software design pattern in the creation of web applications is the three-layer architecture, usually referred to as the three-tier architecture. Each layer in this design oversees handling a particular task according to the separation of concerns principle. The presentation layer, the application layer, and the data layer are the three layers.
## The Presentation Layer
The task of providing information to the user in a meaningful fashion fall under the purview of the presentation layer, also referred to as the user interface layer. The user interacts with the application's front end through this layer. Input from the user, data display, and data formatting for presentation are all under its purview. Since it is not intended to interact with other layers, it should not have any business logic.
The presentation layer in a web application is typically composed of HTML, CSS, and JavaScript. The page's HTML structure, CSS styling, and JavaScript user interaction are all created using these three languages.
## The Application Layer
Information presented to the user in a meaningful fashion is the responsibility of the presentation layer, commonly referred to as the user interface layer. The user interacts with this layer, which is the front end of the application. Input from users, data display, and data formatting for presentation are all its responsibilities. This layer should not contain any business logic as it is intended to be independent of the other layers.
The HTML, CSS, and JavaScript components of a web application often make up the presentation layer. The page's structure is created using HTML, its styling is created using CSS, and user interaction is managed by JavaScript.
## The Data Layer
The task of storing and retrieving data from a database or other data storage mechanism is under the purview of the data layer, sometimes referred to as the persistence layer. The management of all database activities, such as the addition, modification, and deletion of data, falls under the purview of this layer.
The display layer and the application layer are not intended to interact with the data layer. As a result, the data can be quickly accessed and changed without having an impact on other system components. A database management system like MySQL, Oracle, or Microsoft SQL Server is generally used to implement the data layer in a web application.




## Implementation of Three Layer Architecture 
The three-layer design can be implemented using a variety of frameworks and programming languages. An outline of how to use this architecture is provided here:
### Presentation Layer:
The user input and data display are handled by the presentation layer. This layer is frequently implemented in online applications utilizing HTML, CSS, and JavaScript. The page's structure is provided by HTML, its styling is done by CSS, and user interaction is managed by JavaScript.
### Application Layer:
The business logic of the application is implemented at the application layer. It takes orders from the presentation layer, makes the appropriate calculations, and then sends the answers back. Java, C#, or PHP are examples of server-side programming languages that are used to implement the application layer. Additionally, it may make use of frameworks like Spring, ASP.NET, or Laravel.
### Data Layer:
Data storage and retrieval from a database or other data storage technologies fall under the purview of the data layer. It manages all database interactions, such as adding, updating, and deleting data. A database management system like MySQL, Oracle, or Microsoft SQL Server is used to implement the data layer. Additionally, it has the option of using Object-Relational Mapping (ORM) frameworks like Doctrine, Entity Framework, or Hibernate.
### To implement the three-layer architecture, follow these steps:
1.	Determine the system's components and the layer to which they belong.
2.	For each system layer, distinct directories or packages should be created.
3.	Define the boundaries that separate the levels. For instance, the application layer needs to provide the ways the presentation layer can use to get information or carry out tasks.
4.	Separately implement the logic for each layer. Business logic shouldn't be included in the presentation layer, and the application layer shouldn't communicate with the database directly.
5.	Make the code easier to maintain by using appropriate design patterns, such as Model-View-Controller (MVC), to ensure the separation of concerns.
6.	To make sure it is operating properly, test each layer separately.
7.	Integrate the layers, then test the entire system.
The three-layer architecture must be implemented with a thorough understanding of the system's needs, the relevant programming languages and frameworks, and software design concepts. This architecture can aid in developing strong, scalable, and stable applications with careful planning and attention to detail.


### Advantages and Disadvantages of Three-Layer Architecture 
### Advantages of Three-Layer Architecture:

### Modularity: 
The presentation, application, and data layers are separated by the three-layer architecture, which makes it simpler to alter and manage the system over time. Because of this modularity, developers may work independently on each layer without influencing the others.
### Scalability: 
The three-layer architecture enables autonomous scaling of each layer to manage the rising demand. This implies that more servers can be added to accommodate high traffic levels at the application layer without compromising the display or data layer.
### Maintainability: 
Each layer can be individually scaled to manage the additional demand thanks to the three-layer architecture. The presentation or data layer won't be impacted if the application layer experiences excessive traffic because more servers can be added to accommodate the demand.
### Security: 
The security of the system is enhanced by the division of the data layer from the application and presentation layers. It is simpler to manage who has access to the data and avoid unwanted access by restricting access to the data layer.
### Disadvantages of Three-Layer Architecture:
### Complexity: 
The data layer's division from the application and display layers contributes to the system's increased security. Controlling who has access to the data and preventing unwanted access is made simpler by restricting access to the data layer.
### Overhead: 
The security of the system is aided by the data layer's division from the application and display layers. Access to the data layer can be restricted to make it simpler to manage who has access to the data and avoid unwanted access.
### Cost: 
The three-layer design can be more expensive to implement than other architectures since it calls for more resources and knowledge.
### Duplication of Code:
The three-layer architecture can occasionally lead to code duplication between layers. This may lengthen the development process and make system maintenance more challenging.
In most instances, the benefits of the three-layer architecture exceed the drawbacks. While enhancing security, it offers modularity, scalability, and maintainability. However, before choosing to employ this design, it is crucial to carefully assess the difficulty and expense of its implementation.

### Conclusion 
In rare circumstances, the three-layer architecture might lead to code duplication between the layers. Because of this, the system may become more challenging to maintain and take longer to develop.
The three-layer architecture has benefits that, for the most part, exceed its drawbacks. It increases security while providing modularity, scalability, and maintainability. Before selecting to employ this architecture, it is crucial to carefully weigh its complexity and expense.