Design Patterns | Builder

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1. References
2. Example
   • The Product
   • The Concrete Product
   • The Builder
   • The Concrete Builder
   • The Director
   • A simple class to test the Builder design pattern

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1. References
   • Definition: (source: http://en.wikipedia.org/wiki/Builder_pattern)
     
     The intent of the Builder design pattern is to separate the construction of a complex object from its representation.
     By doing so the same construction process can create different representations.
     
     
   • Class diagram: (source: http://en.wikipedia.org/wiki/Builder_pattern)
     
     
2. Example
   • The Product:
     
     public interface Session { public String sendRequest(final String request); }
     
   • The Concrete Product:
     
     public class HttpSession implements Session { public String sendRequest(final String request) { return "http response"; } }
     
   • The Builder:
     
     public interface SessionBuilder { public Session getSession(); public void createSession(); public void configureSession(); }
     
   • The Concrete Builder:
     
     public class HttpSessionBuilder implements SessionBuilder { private Session session; public Session getSession() { return session; } public void createSession() { this.session = new HttpSession(); // do something else with the created session ... } public void configureSession() { // configure the session ... } }
     
   • The Director:
     
     public class SessionDirector { private SessionBuilder sessionBuilder; public SessionDirector(final SessionBuilder sessionBuilder) { this.sessionBuilder = sessionBuilder; } public Session build() { sessionBuilder.createSession(); sessionBuilder.configureSession(); return sessionBuilder.getSession(); } }
     
   • A simple class to test the Builder design pattern:
     
     public class BuilderPatternTest { public static void main(String[] args) { // create the builder final SessionBuilder sessionBuilder = new HttpSessionBuilder(); // create the director final SessionDirector sessionDirector = new SessionDirector(sessionBuilder); // create the session final Session session = sessionDirector.build(); // call methods final String response = session.sendRequest("request"); System.out.println(response); } }