Dependency injection when you only have one dependency JavaZone Johannes Brodwall, Recovering Spring User Steria Norway

Let’s get rid of dogmatic dependency injection

Does this look familiar?

Person- Controller Person- Controller- Impl Person- Service Person- ServiceImpl Person- Repository Impl Person- Repository Impl PersonDao Impl PersonDao Impl Session- Factory

Customer Invoice Order Product

No more: this.personService = new PersonServiceImpl(sessionFactory)

Instead:

private PersonService personService;

Why?

(dear God, why?!)

Testing

Multiple implementations

(Really?)

Configuration

(Often one)

Ordnung muss sein!

(Ordnung muss sein!) Hobgoblin of little minds - Ralph Waldo Emerson

Alternative

Session- Factory PersonController Service Repo sitory

public class PersonController { private PersonService public PersonController(SessionFactory sf) { this.personService = new PersonServiceImpl(sf); }

public class PersonController { private PersonService public PersonController(SessionFactory sf) { this.personService = new PersonServiceImpl(sf); } public class PersonServiceImpl implements … { private PersonRepository personRepo; public PersonServiceImpl(SessionFactory sf) { this.personRepo = new PersonRepositoryImpl(sf); }

public class PersonController { private PersonService public PersonController(SessionFactory sf) { this.personService = new PersonServiceImpl(sf); } public PersonControllerImpl(PersonService ps) { this.personService = ps; }

public class PersonController { private PersonService public PersonController(SessionFactory sf) { this.personService = new PersonServiceImpl(sf); } public PersonControllerImpl(PersonService ps) { this.personService = ps; } For Spring For mocking

SPRING! Session- Factory PersonController Service Repo sitory InvoiceController Repository FooServiceImpl ReportsController FooController

Look ma! No Spring!

Session- Factory PersonServlet Locator (singleton O_O) Locator (singleton O_O) ”Injected” by servlet

public class PersonController extends HttpServlet { private PersonService personService; public PersonController() { } public PersonController(PersonService personService) { this.personService = personService; public void init() throws ServletException { SessionFactory sf = HibernateLookup.getInstance(getServletContext()); this.personService = new PersonServiceImpl(sf); }

public class PersonController extends HttpServlet { private PersonService personService; public PersonController() { } public PersonController(PersonService personService) { this.personService = personService; public void init() throws ServletException { SessionFactory sf = HibernateLookup.getInstance(getServletContext()); this.personService = new PersonServiceImpl(sf); } For mocking Look, ma! No Spring!

Session- Factory PersonController Service Repo sitory InvoiceController Repository FooServiceImpl ReportsController FooController >

Bonus: Generic Repository

public interface Repository { T retrieve(Class type,Serializable id); Serializable save(Object object); List find(Specification spec); Transaction beginTransaction(); }

@RunWith(RepositoryTestRunner.class) public class PersonControllerTest { private Repository repository; private PersonController personController; public PersonControllerTest(Repository repo) { this.repository = repo; this.personController = new PersonController(repo); }

@Test public void should_show_person() { Person person = new Person(); Long id = (Long) repository.save(person); ModelAndView show = personController.show(id); assertEquals(person, show.getModel().get("person")); }

public class RepoTestRunner extends Suite { public RepoTestRunner(Class testClass) { super(testClass, createRunners(testClass)); } static List createRunners(Class testClass) { List runners = new ArrayList (); runners.add(testRunner(testClass, new HashMapRepository())); if (!isRunningInInfinitest()) { runners.add(testRunner(testClass, hibernateRepository())); } return runners; }

What Spring taught me

Be aware of dependencies!

Avoid differences between test and prod

Stay the heck away from frameworks!

Collapse service chains

Takk for meg!