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ArchitecturalDecouplingAbout 1 min


Layers is an architectural pattern where software responsibilities are divided among the different
layers of the application.


Real world example

Consider a website displaying decorated cakes for weddings and such. Instead of the web page
directly reaching into the database, it relies on a service to deliver this information. The
service then queries the data layer to assimilate the needed information.
In plain words

With Layers architectural pattern different concerns reside on separate layers. View layer is
interested only in rendering, service layer assembles the requested data from various sources, and
data layer gets the bits from the data storage.
Wikipedia says

In software engineering, multitier architecture (often referred to as n-tier architecture) or
multilayered architecture is a client–server architecture in which presentation, application
processing, and data management functions are physically separated.

Programmatic Example

On the data layer, we keep our cake building blocks. Cake consist of layers and topping.

public class Cake {
  private Long id;
  @OneToOne(cascade = CascadeType.REMOVE)
  private CakeTopping topping;
  @OneToMany(cascade = CascadeType.REMOVE, fetch = FetchType.EAGER)
  private Set<CakeLayer> layers;

The service layer offers CakeBakingService for easy access to different aspects of cakes.

public interface CakeBakingService {
  void bakeNewCake(CakeInfo cakeInfo) throws CakeBakingException;
  List<CakeInfo> getAllCakes();
  void saveNewTopping(CakeToppingInfo toppingInfo);
  List<CakeToppingInfo> getAvailableToppings();
  void saveNewLayer(CakeLayerInfo layerInfo);
  List<CakeLayerInfo> getAvailableLayers();

On the top we have our View responsible of rendering the cakes.

public interface View {
  void render();
public class CakeViewImpl implements View {
  private final CakeBakingService cakeBakingService;
  public CakeViewImpl(CakeBakingService cakeBakingService) {
    this.cakeBakingService = cakeBakingService;
  public void render() {
    cakeBakingService.getAllCakes().forEach(cake ->;

Class diagram

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Use the Layers architecture when

  • You want clearly divide software responsibilities into different parts of the program.
  • You want to prevent a change from propagating throughout the application.
  • You want to make your application more maintainable and testable.