Systematyczny architekt na drodze ku planowanemu postarzaniu
O mnie : Jarosaw Paka
Who am I?
Journeyman through space, timeandtechnology
devoted follower in church of JVM
Archaeologist of legacy code
chief architect @ Lumesse
owner/founder @ symentis.pl
blogger @ geekyprimitives.wordpress.com
philosopher @ twitter:j_palka
code mangler @ bitbucket:kcrimson & github:jpalka
evil emperor @ 4developers architecture track
Created weakness for the numbers on the boardAbsurd amount of
things, obsolete creationThe lust for always more, indulgence in
hungerA greed for power, the demon needs to feedDesigned for
failureGojira Planned Obsolescence
strategia producenta, majca na celu takie projektowanie towarw,
aby miay one ograniczony czas uytecznego ycia, po tym za okresie
staway si niesprawne, a czsto nieopacalne w naprawie. Towary te
zwykle psuj si zaraz po upywie gwarancji.Wikipedia
Techniki planowanego postarzania
najlepiej na wczoraj
si poprawi jutro (jutro nie nadejdzie nigdy)
to tylko prototyp (artowalimy)
nie mamy czasu (to po co si zabieracie za ten projekt?)
Jakby tego byo mao
trendy
We are fashion industryUncle Bob
Rewrite
Offload
Modernization
Next Generation Something
Kilka lat pniej
Rewrite
Offload
Modernization
Next Generation Something
I znowy trzeba przepisa
Dobry inynier,Id szukaj business value,szukaj
Podejcie Big-Bang
Uczymy si na ywym organizmie
Ludzie z businessu trzymaj si na dystans
Brak zrozumienia domeny problemu
It is up to us to live up to the legacy that was left for us,
and to leave a legacy that is worthy of our children and of future
generations.Christine Gregoire
Nie naprawimy przeszoci,Ale moemy uczyni przyszo lepsz
Mzg, cobdziemy dzi robi?
Dodamy kolejny framework!
Przygotujmy si na lepsz przyszo
Przygotujmy si na zmiany
Abstrakcje
Posugujemy si nimi na co dzie
S zapisane w naszej podwiadomoci
Dlatego tak trudno o nich rozmawia
Znaczenie ukryte za fasad sw
Czy mgby otworzy zamek?
Brak jednoznacznoci abstrakcji
Znaczenie = abstrakcja(kontekst)
Polimorfizm
public interface TalkingAboutAbstractions{
public void createEmployee(String candidate);
}
public vois hireCandidate(){
String candidate = "Jan
Kowalski";employeeBean.createEmployee(candidate);
candidate = "123456";employeeBean.createEmployee(candidate);
candidate = "{ candidate : {id : \"123456\"}
}";employeeBean.createEmployee(candidate);
}
public interface TalkingAboutAbstractions{
public Employee hireCandidate(Suppliercandidate);
}
public interface GuessWhatIHaveInMind{
String serverStatus() throws Exception;
}
OK
Mam si dobrze
Cholera gdzie jest dysk?
Daj mi spokj
!@#$%^&*()
public interface GuessWhatIHaveInMind{
public enum ServerStatus { OK, BUSY, INTERNAL_ERROR }
ServerStatus serverStatus() throws Exception;
}
A teraz czas na co z klasyki
Prawdziwy, Autentyczny,jedyny
Brainfuck
public class BrainFuck extends GenericHibernateDAO{
List processList(String target, Long id);
}
public class BrainFuck extends GenericHibernateDAO{
ResultSet processList(String target, Long id);
}
Use types, Luke!
Mie i by, to nie to samo
Diabe tkwi w szczegach
Generalizacja, uoglnienieis-a
Kompozycja, delegacjahas-a
Uoglniaj na poziomie kontraktuInterfejsu ze wiatem
zewntrznym
Kompozycja i delegacjagdy przychodzi czasna Szczegy
implementacji
Stosuj obie techniki wiadomie,Naucz si stosowa je wymiennie
Polimorfizm przychodzi W wielu smakach(dziedziczenie to tylko
jeden z nich)
Ad hocParametricCoercionInclusion (subtyping)
Buisness logic system constructioncode infrastructure
public class SoftwareConstruction implements BeanFactoryAware,
DisposableBean {
@Override@SuppressWarnings("unchecked")public void
setBeanFactory(final BeanFactory beanFactory) throws BeansException
{consumerConfigurations = (Map)(Object) ((ListableBeanFactory)
beanFactory).getBeansOfType(ConsumerConfiguration.class);}
}
Nie mieszajmy odpowiedzialnoci
Odpowiedzialno to nie tylko business features
Obiekt nie moe by odpowiedzialny za skonstruowanie samego
siebie
public AlbumPage(PageParameters parameters)
{super(parameters);
boolean showDescription = false;
List albums;String searchQuery =
parameters.get("search").toString(null);
if (searchQuery == null) {searchQuery =
parameters.get(0).toString(null);if (searchQuery != null)
{showDescription = true;}}
albums = productCatalog.searchAlbums(searchQuery);
ListView albumsListView = new AlbumsListView(ID_ALBUMS_VIEW,
albums, showDescription);
add(albumsListView);}
public interface ShowMeMore{
@GETpublic Response getRoot(@Context HttpServletRequest
request);
}
public class ShowMeMoreImpl implements ShowMeMore{
@Contextprivate HttpServletRequest request;
@GETpublic Response getRoot();
}
Struktura systemu
Gsto informacji
Hierarchies are brilliant systems inventions, not only because
they give a systemstability and resilience, but also because they
reduce the amount of information thatany part of the system has to
keep track of.
Hierarchies are brilliant systems inventions, not only because
they give a systemstability and resilience, but also because they
reduce the amount of information thatany part of the system has to
keep track of.
In hierarchical systems relationships within each subsystem are
denser and strongerthan relationships between subsystems.
Everything is still connected to everythingelse, but not equally
strongly.
In hierarchical systems relationships within each subsystem are
denser and strongerthan relationships between subsystems.
Everything is still connected to everythingelse, but not equally
strongly.
Hierarchical systems are partially decomposable. Their
subsystems with theirespecially dense information links can
function at least partially as systems in theirown right. When
hierarchies break down, they usually split along their
subsystemboundariesDonella Meadows
Hierarchical systems are partially decomposable. Their
subsystems with theirespecially dense information links can
function at least partially as systems in theirown right. When
hierarchies break down, they usually split along their
subsystemboundaries
Value is Your Subsystem Boundary
Kandydat
AplikantKandydat
AplikantKandydatBezrobotny
AplikantKandydatBezrobotny
Value is usually Your subsystem boundary
Encapsulation is the packing of data and functions into a single
component.
Hierarchies are brilliant systems inventions, not only because
they give a systemstability and resilience, but also because they
reduce the amount of information thatany part of the system has to
keep track of.
public class WrongEncapsulation{public String name;}
public class IsItEncapsulation{private String name;}
public class JavaStyleEncapsulation{private String name;
public String getName(){ ... };
public void setName(String name){ };
}
Software design porn
public class AnotherStylishClass{
private List strings = new ArrayList();
public List getStrings(){return strings;}
AnotherStylishCase obj = new AnotherStylishCase();
obj.getStrings().add("Hello leaky abstraction!");
}
Testabilitythe ultimate UI
If it's hard to test it will be hard to maintain and even harder
to rewritesomebody on the internet
Jakie s granice szalestwa ...
Kiedy znowu zobaczysz Java Bean,usu go,powanie,natychmiast,git
rm AnotherStupidJavaBean.java
Jedyne rzeczy ktre warto zapamita
AbstrakcjePolimorfizmContext is King
Gsto informacjiEnkapsulacjaHierarchical Systems
Software construction vs business logic
