java se 8 for java ee developers

Others Talk, We Listen.

Java SE 8 for Java EE DevelopersReza RahmanSenior [email protected]@reza_rahman

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Java SE 8 and Java EE

• Java SE 8 is one of the most significant releases in years• Extremely well adopted

• Most Java EE 7 runtimes support Java SE 8• Java SE 8 can already be used well with Java EE

• There are gaps that need to be met in Java EE 8


Lambdas

• Introducing functional programming without breaking Java• Imperative to Declarative• Requires change in thinking to become true believer• Practical benefits for the rest of us• Streams, CompletableFuture• Forward compatible – good for use with Java EE 7

• An actual syntax change at the language level• Syntactic sugar over anonymous inner classes?• Parameterized business logic as data


Lambdas


The Problem

List<Student> students = ...double highestScore = 0.0;for (Student s : students) { if (s.gradYear == 2011) { if (s.score > highestScore) { highestScore = s.score; } }

Lambdas


An Inelegant Solution

List<Student> students = ...double highestScore = students. filter(new Predicate<Student>() { public boolean op(Student s) { return s.getGradYear() == 2011; } }). map(new Mapper<Student,Double>() { public Double extract(Student s) { return s.getScore(); } }). max();

Lambdas


The Elegant Solution

SomeList<Student> students = ...double highestScore = students. filter(Student s -> s.getGradYear() == 2011). map(Student s -> s.getScore()). max();

Asynchronous Servlet and Lambdas


@WebServlet(urlPatterns={"/report"}, asyncSupported=true)public class AsyncServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) { ... final AsyncContext asyncContext = request.startAsync(); asyncContext.start(() -> { ReportParameters parameters = parseReportParameters(asyncContext.getRequest()); Report report = generateReport(parameters); printReport(report, asyncContext); asyncContext.complete(); }); }}

Streams

• Applying lambdas to the Collections API• Bulk operations• Sequence (“stream”) of data• Filter, map, reduce

• Performance, performance, performance• Lazy processing• Parallel processing


Streams


Pipeline

• A stream pipeline consists of three parts• A source• Zero or more intermediate operations• A terminal operation

int sum = transactions.stream(). filter(t -> t.getBuyer().getCity().equals(“Philly”)). mapToInt(Transaction::getPrice). sum();

Source

Intermediate operation

Terminal operation

JSON-P Stream


[ { "name":"Duke", "gender":"male", "phones":[ "home":"650‐123 ‐4567", "mobile":"650 ‐111 ‐2222" ] }, { "name":"Jane", ...]

JsonArray contacts = Json.createArrayBuilder() .add(...

JSON-P Stream


Map<String, Long> names = contacts.getValuesAs(JsonObject.class).stream() .filter(x -> "female".equals(x.getString("gender"))) .map(x -> (x.getString("name"))) .collect( Collectors.groupingBy( Function.identity(), Collectors.counting() ) );

Date/Time API

• Significant improvement over current Java date types• Date, Calendar

• Unified, comprehensive, modern model• Builder pattern, fluent API• Manipulating temporal values• Better internationalization


Date/Time API


Key Artifacts

• LocalTime• LocalDate• LocalDateTime• ZonedDateTime

• Instant• Duration• Period

Date/Time API Examples

// Get the current date and timeLocalDateTime now = LocalDateTime.now();

// Returns formatted date and time // “2013-10-21T20:25:15:16.256”now.toString();

// Add 5 hoursLocalDateTime later = now.plus(5, HOURS);

// Subtract 2 daysLocalDateTime earlier = now.minus(2, DAYS);


More Date/Time API Examples

LocalDate today = LocalDate.now();LocalDate bday = LocalDate.of(1979, 3, 10);Period timeAlive = Period.between(bday, today);int age = timeAlive.getYears();

// Periods can also be used as arguments in the .plus() // and .minus() methodsLocalDate calculatedBday = today.minus(timeAlive);


The Date/Time API with JPA

• JPA does not yet support the Date/Time API• This is a high priority item to fix in Java EE 8

• It is possible to use JPA converters as a workaround• Latest versions of Hibernate does support the Date/Time API


Date/Time API with JPA


Using JPA Converters

@Entitypublic class Accident {

@Convert(converter=InstantConverter.class) @Temporal(TemporalType.TIME) private Instant when;}

Date/Time API with JPA


Using JPA Converters

@Converterpublic class InstantConverter implements AttributeConverter<Instant, Date> {

public Date convertToDatabaseColumn(Instant instant) { return Date.from(instant); }

public Instant convertToEntityAttribute(Date date) { return date.toInstant(); }}

The Date/Time API with JSF

• JSF does not yet support the Date/Time API• This is a high priority item to fix in Java EE 8• Code to introduce change has already been contributed to JSF 2.3 by

community• JSF converters can be used as workaround


Date/Time API with JSF


Using JSF Converters

@FacesConverter(“InstantConverter”)public class InstantConverter implements Converter {

@Override public Object getAsObject(FacesContext ctx, ..., String value) { return Instant.parse(value); } ...




... @Override public String getAsString(FacesContext ctx, ..., Object value) { DateTimeFormatter formatter = DateTimeFormatter .ofLocalizedDateTime(FormatStyle.SHORT) .withLocale(Locale.US) .withZone(ZoneId.systemDefault());

return formatter.format((TemporalAccessor) value); }}




<h:form> <h:inputText id = “date” value = “#{registerAccident.when}” size = “20” required=“true” label = “when” converter = “instantConverter” /> ...

@Named @ViewScopedpublic class RegisterAccident { Instant when; ...

Repeatable Annotations

• In Java SE 8, annotations can now be repeated• A lot of applicability in Java EE

• @DataSourceDefinition• @NamedQuery• @JMSDestinationDefinition• @JMSConnectionFactoryDefinition• @MailSessionDefinition• @Schedule

• Few cases have been addressed, many remain


Repeatable Annotations in Java EE


@NamedQueries({ @NamedQuery(name=SELECT_ALL, query="..."), @NamedQuery(name=COUNT_ALL, query="...")})public class Customer { ...

@NamedQuery(name=SELECT_ALL, query="...")@NamedQuery(name=COUNT_ALL, query="...")public class Customer { ...

Completable Future

• Futures and callbacks both have serious flaws• Especially when it comes to significantly “reactive” code

• CompletableFuture significantly better• Non-blocking, event-driven, composable and functional (via lambdas)


Looks are Deceiving…

Person p = ...Assets assets = getAssets(p);Liabilities liabilities = getLiabilities(p);Credit credit = calculateCreditScore(assets, liabilities);

History history = getHealthHistory(p);Health health = calculateHeathScore(history);

Coverage coverage = underwrite(credit, health);


The Problem with Futures (and Callbacks)

Person p = ...Future<Assets> f1 = executor.submit(() -> getAssets(p));Future<Liabilities> f2 = executor.submit( () -> getLiabilities(p));Future<Credit> f3 = executor.submit( () -> calculateCreditScore(f1.get(), f2.get()));

// The unrelated calls below are now blocked for no reasonFuture<History> f4 = executor.submit(() -> getHealthHistory(p));Future<Health> f5 = executor.submit( () -> calculateHeathScore(f4.get()));

// Unrelated paths join belowFuture<Coverage> f6 = executor.submit( () -> underwrite(f3.get(), f5.get()));


Callbacks don’t block, but introduce callback hell…https://github.com/m-reza-rahman/reactive_javaee/blob/master/CallbackHell.java

https://github.com/m-reza-rahman/reactive_javaee/blob/master/CallbackHell.java

CompletableFuture Basics

public CompletableFuture<Confirmation> processPayment( Order order) { CompletableFuture<Confirmation> future = new CompletableFuture<>(); executor.execute(() -> { Confirmation status = ... future.complete(status); }); return future;}


paymentService .processPayment(order) .thenAccept( confirmation -> System.out.println(confirmation));

Functional Reactive to the Rescue?

CompletableFuture<Assets> getAssets = CompletableFuture.supplyAsync(() -> getAssets(person));CompletableFuture<Liabilities> getLiabilities = CompletableFuture.supplyAsync(() -> getLiabilities(person));CompletableFuture<Credit> calculateCreditScore = getAssets.thenCombineAsync(getLiabilities, (assets, liabilities) -> calculateCreditScore(assets, liabilities));

CompletableFuture<Health> calculateHeathScore = CompletableFuture.supplyAsync(() -> getHealthHistory(person)) .thenApplyAsync(history -> calculateHeathScore(history));

Coverage coverage = calculateCreditScore.thenCombineAsync(calculateHeathScore, (credit, health) -> underwrite(credit, health)).join();


@Asynchronous + CompletableFuture


@Asynchronouspublic Future<Confirmation> processPayment(Order order) { ... Confirmation status = ...; return new AsyncResult(status);

}

@Asynchronouspublic CompletableFuture<Confirmation> processPayment( Order order) { ... Confirmation status = ...; return CompletableFuture<Confirmation>.completedFuture(status);}

Java EE Guardians

http://javaee-guardians.io@javaee_guardian


http://javaee-guardians.io/

Summary

• Java SE 8 is one of the most significant releases in years• Most Java EE 7 runtimes support Java SE 8• Java SE 8 can already be used well with Java EE• There are gaps that need to be met in Java EE 8


Resources

• Java EE Tutorials• http://docs.oracle.com/javaee/7/tutorial/doc/home.htm

• Java SE Tutorials• http://docs.oracle.com/javase/tutorial/

• What's New in JDK 8• http://www.oracle.com/technetwork/java/javase/8-whats-new-

2157071.html• Digging Deeper

• http://docs.oracle.com/javaee/7/firstcup/doc/home.htm• https://glassfish.java.net/hol/• http://cargotracker.java.net


http://docs.oracle.com/javaee/7/tutorial/doc/home.htm

http://docs.oracle.com/javaee/7/tutorial/doc/home.htm

http://docs.oracle.com/javase/tutorial/

http://docs.oracle.com/javaee/7/firstcup/doc/home.htm

http://docs.oracle.com/javaee/7/firstcup/doc/home.htm

https://glassfish.java.net/hol/

https://glassfish.java.net/hol/

http://cargotracker.java.net/

http://cargotracker.java.net/

java se 8 for java ee developers

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