Builder Pattern

2023-12-24 in Design Patterns

Builder Pattern에 대해 설명하는 페이지입니다.

Environment

• Programming Language: Java

Index

• Index
• Introduction
• Characteristics
• Participants
• How to Use (Example)
• Comments

Introduction

• Purpose
  • Allows for the dynamic creation of objects based upon easily interchangeable algorithms.
• Use When
  • Runtime control over the creation process is required.
  • Multiple representations of creation algorithms are required.
  • Object creation algorithms should be decoupled from the system.
  • The addition of new creation functionality without changing the core code is necessary.

Characteristics

• Director knows what parts are needed for the final product
• Concrete builder knows how to produce the part and add it to the final product.
• A Builder is a Strategy that is specialized to create a composite object or data structure
• Builder constructs the object step-by-step and the result is requested at a later stage

Participants

• Client
  • selects director and concrete builder to build the product
  • asks concrete builder to return final constructed product
• Director
  • knows what steps it takes to build a product
  • but it does not know how each step is to be carried out
• Builder
  • specifies an abstract interface for creating parts of a Product object
• Concrete Builder
  • constructs and assembles parts of the product by implementing the Builder interface
  • defines and keeps track of the representation it creates
  • provides an interface for retrieving the product
• Product
  • represents the complex object under construction

How to Use (Example)

• Director

  public class AerospaceEngineer {
      private AirplaneBuilder airplaneBuilder;
    
      public void setAirplaneBuilder(AirplaneBuilder ab) {
          airplaneBuilder = ab;
      }
    
      public Airplane getAirplane() {
          return airplaneBuilder.getAirplane();
      }
    
      public void constructAirplane() {
          airplaneBuilder.createNewAirplane();
          airplaneBuilder.buildWings();
          airplaneBuilder.buildPowerplant();
          airplaneBuilder.buildAvionics();
          airplaneBuilder.buildSeats();
      }
  }
  

• Abstract Builder

  public abstract class AirplaneBuilder {
      protected Airplane airplane;
      protected String customer;
      protected String type;
    
      public Airplane getAirplane() {
          return airplane;
      }
    
      public void createNewAirplane() {
          airplane = new Airplane(customer, type);
      }
    
      public abstract void buildWings();
      public abstract void buildPowerplant();
      public abstract void buildAvionics();
      public abstract void buildSeats();
  }
  

• Product

  public class Airplain {
      private String type;
      private float wingspan;
      private String powerplant;
      private int crewSeats;
      private int passengerSeats;
      private String avionics;
      private String customer;
  
      public Airplain(String customer, String type) {
          this.customer = customer;
          this.type = type;
      }
  
      public void setWingspan(float w) {
          this.wingspan = w;
      }
  
      public void setPowerplant(String p) {
          this.powerplant = p;
      }
    
      public void setAvionics(String a) {
          this.avionics = a;
      }
    
      public void setNumberSeats(int crewSeats, int passengerSeats) {
          this.crewSeats = crewSeats;
          this.passengerSeats = passengerSeats;
      }
    
      public String getCustomer() {
          return customer;
      }
    
      public String getType() {
          return type;
      }
  }
  

• Concrete Builder

  public class CropDuster extends AirplaneBuilder {
      public CropDuster (String customer) {
          super.customer = customer;
          super.type = "Crop Duster v3.4";
      }
    
      public void buildWings() {
          airplane.setWingspan(9f);
      }
    
      public void buildPowerplant() {
          airplane.setPowerplant("single piston");
      }
    
      public void buildAvionics() {}
    
      public void buildSeats() {
          airplane.setNumberSeats(1,1);
      }
  }
  

• Client

  public class BuilderExample {
      public static void main(String[] args) {
          // instantiate the director (hire the engineer)
          AerospaceEngineeraero = new AerospaceEngineer();
  
          // instantiate each concrete builder (take orders)
          AirplaneBuildercrop = new CropDuster("Farmer Joe");
          AirplaneBuilderfighter = new FighterJet("The Navy");
          AirplaneBuilderglider = new Glider("Tim Rice");
  
          // build a CropDuster
          aero.setAirplaneBuilder(crop);
          aero.constructAirplane();
          Airplane completedCropDuster= aero.getAirplane();
          System.out.println(completedCropDuster.getType() +
              " is completed and ready for delivery to " +
              completedCropDuster.getCustomer());
  }
  

Comments

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