This document discusses several popular Java libraries including: - Dependency injection frameworks like Guice and Spring - Logging with SLF4J - Collections and utilities with Guava - HTTP clients like OkHttp - Reactive programming with RxJava - REST with Retrofit - Asynchronous programming with JDeferred - Event handling with MBassador - Code generation with Lombok and ByteBuddy - Testing utilities like JUnitParams, Mockito, Jukito, and Spock - Waiting assertions with Awaitility and REST testing with Rest-assured.

1. @aalmiray #DevoxxPL
JAVA LIBRARIES
YOU CAN’T
AFFORD TO MISS
ANDRES ALMIRAY
@AALMIRAY

2. @aalmiray #DevoxxPL

3. @aalmiray #DevoxxPL
DEPENDENCY
INJECTION

4. @aalmiray #DevoxxPL
Guice - https://github.com/google/guice
Injector injector = Guice.createInjector(new AbstractModule() {
@Override
protected void configure() {
bind(Engine.class).annotatedWith(named("efficient"))
.to(FusionPoweredEngine.class)
bind(Engine.class).annotatedWith(named("poor"))
.to(CoalPoweredEngine.class)
}
});
Key key = Key.of(Engine.class, named("poor"));
Engine engine = injector.getInstance(key);
// do something with engine

5. @aalmiray #DevoxxPL
Spring - http://projects.spring.io/spring-framework/
• More than just dependency injection
• Assertions
• MessageSource + MessageFormat
• Serialization
• JDBC, JPA
• JMX
• Validation
• Scheduling
• Testing

6. @aalmiray #DevoxxPL
BEHAVIOR

7. @aalmiray #DevoxxPL
SLF4J - http://www.slf4j.org/
• Wraps all other logging frameworks:
• java.util.logging
• Apache commons logging
• Log4j
• Provides varargs methods

8. @aalmiray #DevoxxPL
Guava - https://github.com/google/guava
• New Collections:
• MultiSet
• BiMap
• MultiMap
• Table
• Utility classes for Collections
• Utility classes for String
• Caches
• Reflection
• I/O
• Functional programming support (JDK6+)

9. @aalmiray #DevoxxPL
OkHttp - http://square.github.io/okhttp/
public static final MediaType JSON
= MediaType.parse("application/json; charset=utf-8");
OkHttpClient client = new OkHttpClient();
String post(String url, String json) throws IOException {
RequestBody body = RequestBody.create(JSON, json);
Request request = new Request.Builder()
.url(url)
.post(body)
.build();
Response response = client.newCall(request).execute();
return response.body().string();
}

10. @aalmiray #DevoxxPL
RxJava - http://reactivex.io/
Observable<Repository> observable = github.repositories(model.getOrganization());
if (model.getLimit() > 0) {
observable = observable.take(model.getLimit());
}
Subscription subscription = observable
.timeout(10, TimeUnit.SECONDS)
.doOnSubscribe(() -> model.setState(RUNNING))
.doOnTerminate(() -> model.setState(READY))
.subscribeOn(Schedulers.io())
.subscribe(
model.getRepositories()::add,
Throwable::printStackTrace);
model.setSubscription(subscription);

11. @aalmiray #DevoxxPL
Retrofit - http://square.github.io/retrofit/
public interface GithubAPI {
@GET("/orgs/{name}/repos")
Call<List<Repository>> repositories(@Path("name") String name);
@GET
Call<List<Repository>>> repositoriesPaginate(@Url String url);
}
Retrofit retrofit = new Retrofit.Builder()
.baseUrl("https://api.github.com")
.addConverterFactory(JacksonConverterFactory.create(objectMapper))
.build();
return retrofit.create(GithubAPI.class);

12. @aalmiray #DevoxxPL
Retrofit + RxJava
public interface GithubAPI {
@GET("/orgs/{name}/repos")
Observable<Response<List<Repository>>> repositories(@Path("name") String
name);
@GET
Observable<Response<List<Repository>>> repositoriesPaginate(@Url String url);
}
Retrofit retrofit = new Retrofit.Builder()
.baseUrl("https://api.github.com")
.addConverterFactory(JacksonConverterFactory.create(objectMapper))
.addCallAdapterFactory(RxJavaCallAdapterFactory.create())
.build();
return retrofit.create(GithubAPI.class);

13. @aalmiray #DevoxxPL
JDeferred - http://jdeferred.org/
model.setState(RUNNING);
int limit = model.getLimit();
limit = limit > 0 ? limit : Integer.MAX_VALUE;
Promise<Collection<Repository>, Throwable, Repository> promise =
github.repositories(model.getOrganization(), limit);
promise.progress(model.getRepositories()::add)
.fail(Throwable::printStackTrace)
.always((state, resolved, rejected) -> model.setState(READY));

14. @aalmiray #DevoxxPL
MBassador - https://github.com/bennidi/mbassador
public class EventHandler {
private static final Logger LOG = LoggerFactory.getLogger(EventHandler.class);
@Inject
private net.engio.mbassy.bus.MBassador<ApplicationEvent> eventBus;
@net.engio.mbassy.listener.Handler
public void handleNewInstance(NewInstanceEvent event) {
LOG.trace("New instance created {}", event.getInstance());
}
public void createInstance() {
eventBus.publish(new NewInstanceEvent(Person.builder()
.name("Andres")
.lastname("Almiray")
.build()));
}
}

15. @aalmiray #DevoxxPL
BYTECODE/
AST

16. @aalmiray #DevoxxPL
Lombok - https://projectlombok.org/
import javax.annotation.Nonnull;
@lombok.Data
public class Person {
private final String name;
private final String lastname;
@Nonnull
@lombok.Builder
public static Person create(@Nonnull String name, @Nonnull String lastname) {
return new Person(name, lastname);
}
}
@lombok.Data
@lombok.EqualsAndHashCode(callSuper = true)
@lombok.ToString(callSuper = true)
public class NewInstanceEvent extends ApplicationEvent {
@javax.annotation.Nonnull
private final Object instance;
}

17. @aalmiray #DevoxxPL
ByteBuddy - http://bytebuddy.net
public class Foo {
public String bar() { return null; }
public String foo() { return null; }
public String foo(Object o) { return null; }
}
Foo dynamicFoo = new ByteBuddy()
.subclass(Foo.class)
.method(isDeclaredBy(Foo.class)).intercept(FixedValue.value("One!"))
.method(named("foo")).intercept(FixedValue.value("Two!"))
.method(named("foo").and(takesArguments(1)))
.intercept(FixedValue.value("Three!"))
.make()
.load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER)
.getLoaded()
.newInstance();

18. @aalmiray #DevoxxPL
TESTING

19. @aalmiray #DevoxxPL
JUnitParams - https://github.com/Pragmatists/JUnitParams
@RunWith(JUnitParamsRunner.class)
@TestFor(SampleService.class)
public class SampleServiceTest {
private SampleService service;
@Rule
public final GriffonUnitRule griffon = new GriffonUnitRule();
@Test
@Parameters({",Howdy stranger!",
"Test, Hello Test"})
public void sayHello(String input, String output) {
assertThat(service.sayHello(input), equalTo(output));
}
}

20. @aalmiray #DevoxxPL
Mockito - http://mockito.org/
@Test @Parameters({",Howdy stranger!", "Test, Hello Test"})
public void sayHelloAction(String input, String output) {
// given:
SampleController controller = new SampleController();
controller.setModel(new SampleModel());
controller.setService(mock(SampleService.class));
// expectations
when(controller.getService().sayHello(input)).thenReturn(output);
// when:
controller.getModel().setInput(input);
controller.sayHello();
// then:
assertThat(controller.getModel().getOutput(), equalTo(output));
verify(controller.getService(), only()).sayHello(input);
}

21. @aalmiray #DevoxxPL
Jukito - https://github.com/ArcBees/Jukito
@RunWith(JukitoRunner.class)
public class SampleControllerJukitoTest {
@Inject private SampleController controller;
@Before
public void setupMocks(SampleService sampleService) {
when(sampleService.sayHello("Test")).thenReturn("Hello Test");
}
@Test
public void sayHelloAction() {
controller.setModel(new SampleModel());
controller.getModel().setInput("Test");
controller.sayHello();
assertThat(controller.getModel().getOutput(),
equalTo("Hello Test"));
verify(controller.getService(), only()).sayHello("Test");
}
}

22. @aalmiray #DevoxxPL
Spock- http://spockframework.org/
@spock.lang.Unroll
class SampleControllerSpec extends spock.lang.Specification {
def "Invoke say hello with #input results in #output"() {
given:
SampleController controller = new SampleController()
controller.model = new SampleModel()
controller.service = Mock(SampleService) {
sayHello(input) >> output
}
when:
controller.model.input = input
controller.sayHello()
then:
controller.model.output == output
where:
input << ['', 'Test']
output << ['Howdy, stranger!', 'Hello Test']
}
}

23. @aalmiray #DevoxxPL
Awaitility - https://github.com/awaitility/awaitility
@Test @Parameters({",Howdy stranger!”, "Test, Hello Test"})
public void sayHelloAction(String input, String output) {
// given:
SampleModel model = mvcGroupManager.findModel("sample", SampleModel.class);
SampleController controller = mvcGroupManager.findController("sample",
SampleController.class);
// expect:
assertThat(model.getOutput(), nullValue());
// when:
model.setInput(input);
controller.invokeAction("sayHello");
// then:
await().until(() -> model.getOutput(), notNullValue());
assertThat(model.getOutput(), equalTo(output));
}

24. @aalmiray #DevoxxPL
Rest-assured - https://github.com/rest-assured/rest-assured
get("/lotto").then().assertThat().body("lotto.lottoId",
equalTo(5));
given().
param("key1",
"value1").
param("key2",
"value2").
when().
post("/somewhere").
then().
body(containsString("OK"));
* Includes JsonPath and XmlPath support

25. @aalmiray #DevoxxPL
HONORARY
MENTIONS

26. @aalmiray #DevoxxPL
Okio - https://github.com/square/okio
HikariCP - https://github.com/brettwooldridge/HikariCP
gRPC - http://www.grpc.io/
Kryo - https://github.com/EsotericSoftware/kryo
MockServer - http://www.mock-server.com/

27. @aalmiray #DevoxxPL
THANK YOU!
ANDRES ALMIRAY
@AALMIRAY