MongoDB and Java 8 Agenda Java8 Main Features MongoDB + Java8 Few - - PowerPoint PPT Presentation

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MongoDB and Java 8 Agenda Java8 Main Features MongoDB + Java8 Few - - PowerPoint PPT Presentation

Apr 11, 2023 18 likes •742 views

MongoDB and Java 8 Agenda Java8 Main Features MongoDB + Java8 Few Examples RX Driver 3 Java 8 MongoDB Java Driver is JAVA6+ Complaint Java 8 Features and Improvements Lambda Expressions New Date API Stream API Type

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MongoDB and Java 8

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3

Agenda

Java8 Main Features MongoDB + Java8 Few Examples RX Driver

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Java 8

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MongoDB Java Driver is JAVA6+ Complaint

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Java 8 Features and Improvements

  • Lambda Expressions
  • New Date API
  • Stream API
  • Type Annotations
  • Compact Profiles
  • Security Enhancements
  • JavaFX Improvements
  • Nashorn JS Engine
  • Unicode Enhancements
  • Selector Provider (IO & NIO)
  • Concurrency
  • …

http://www.oracle.com/technetwork/java/javase/8-whats-new-2157071.html

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Java 8 Features and Improvements

  • Lambda Expressions
  • Stream API
  • New Date API
  • Type Annotations
  • Compact Profiles
  • Security Enhancements
  • JavaFX Improvements
  • Nashorn JS Engine
  • Unicode Enhancements
  • Selector Provider (IO & NIO)
  • Concurrency
  • …

http://www.oracle.com/technetwork/java/javase/8-whats-new-2157071.html

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8

Lambda Function

  • Anonymous Functions

– Not bounded to an identifier – Inline definition – Passed as argument to higher-order functions

  • Functional Java FTW
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Lambda Function

… .map(line -> Arrays.asList(line.split(SEPARATOR SEPARATOR))) ))) … i -> document.put(headers.get(i), values.get(i) )

  • Anonymous Functions

– Not bounded to an identifier – Inline definition – Passed as argument to higher-order functions

  • Functional Java FTW
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Stream API

  • Streams are free flowing

sequence of elements – Pipeline kind of processing

  • Starts with a source of data

(Collections) – Processes elements of that data source in a parallelized fashion – Intermediary processing steps

  • Generally implemented

by lambdas – Terminator operators

  • Streams are immutable!

try try(BufferedReader reader = new new BufferedReader BufferedReader(fr fr)){ )){ return return reader reader.lines .lines() () .skip(1) .skip(1) .map( .map(line line -> {

  • > {

Document document = new new Document(); Document(); List<String> values = Arrays.asList(line.split(SEPARATOR SEPARATOR)); )); IntStream.range(0, Math.min(values.size(), headers.size())) .forEach(i -> document.put(headers.get(i), values.get(i) )); return return document document; }).collect(Collectors.toList());

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Stream API

public public List<Document> List<Document> readRecords readRecords(List<String> (List<String> headers headers) { ) { try try ( (FileReader FileReader fr fr = = new new FileReader FileReader(this this.source source); ); BufferedReader reader = new new BufferedReader BufferedReader(fr fr)) { )) { return return reader reader .lines() .skip(1) .map(line -> { Document document = new new Document(); Document(); List<String> values = Arrays.asList(line .split(SEPARATOR SEPARATOR)); )); IntStream.range(0, Math.min(values.size(), headers.size())) .forEach( i -> document.put(headers.get(i), values.get(i))); return return document document; }).collect(Collectors.toList()); } catch catch ( (IOException IOException e) { ) { throw throw new new UncheckedIOException UncheckedIOException(e); ); } }

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New Date API

  • There is no native support for new Date API
  • Our Codec

Codec API gives the possibility map this data type ( Instant. Instant.class class ) to encode to a driver supported data type and decode back to the original data type

InstantCodec instantCodec = new new InstantCodec InstantCodec(); (); Map<BsonType, Class<?>> replacements = new new HashMap HashMap<BsonType BsonType, Class<?>>(); , Class<?>>(); replacements.put(BsonType.DATE_TIME DATE_TIME, , Instant. Instant.class class); );

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New Date API

public public class class InstantCodec InstantCodec implements implements Codec<Instant> { Codec<Instant> { public public void void encode( encode(BsonWriter BsonWriter writer writer, Instant , Instant value value, EncoderContext encoderContext) { //will store Instant has Epoch Milliseconds writer.writeDateTime(value.toEpochMilli()); } public public Class<Instant> Class<Instant> getEncoderClass getEncoderClass() { () { return return Instant. Instant.class class; } //return back on Instant.class public public Instant decode( Instant decode(BsonReader BsonReader reader reader, , DecoderContext DecoderContext decoderContext decoderContext) { ) { return return Instant. Instant.ofEpochMilli

  • fEpochMilli(reader

reader.readDateTime .readDateTime()); ()); } } http://mongodb.github.io/mongo-java-driver/3.0/bson/codecs/

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New Date API

public public class class InstantCodec InstantCodec implements implements Codec<Instant> { Codec<Instant> { public public void void encode( encode(BsonWriter BsonWriter writer writer, Instant , Instant value value, EncoderContext encoderContext) { //will store Instant has Epoch Milliseconds writer.writeDateTime(value.toEpochMilli()); } public public Class<Instant> Class<Instant> getEncoderClass getEncoderClass() { () { return return Instant. Instant.class class; } //return back on Instant.class public public Instant decode( Instant decode(BsonReader BsonReader reader reader, , DecoderContext DecoderContext decoderContext decoderContext) { ) { return return Instant. Instant.ofEpochMilli

  • fEpochMilli(reader

reader.readDateTime .readDateTime()); ()); } } http://mongodb.github.io/mongo-java-driver/3.0/bson/codecs/

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New Date API

InstantCodec instantCodec = new new InstantCodec InstantCodec(); (); Map<BsonType, Class<?>> replacements = new new HashMap HashMap<BsonType BsonType, Class<?>>(); , Class<?>>(); replacements.put(BsonType.DATE_TIME DATE_TIME, , Instant. Instant.class class); ); CodecRegistry cr = CodecRegistries.fromRegistries( CodecRegistries.fromCodecs(instantCodec), CodecRegistries.fromProviders(documentCodecProvider), MongoClient.getDefaultCodecRegistry()); // add the new code registry has option. MongoClientOptions option = MongoClientOptions.builder() .codecRegistry(cr).build(); mc mc = = new new MongoClient MongoClient("localhost:27017" "localhost:27017", , option

  • ption);

); collection collection = = mc mc.getDatabase .getDatabase("dates" "dates"). ).getCollection getCollection("sample" "sample"); ); Document doc = new new Document( Document("java8date" "java8date", , Instant. Instant.now now()); ()); collection collection.insertOne .insertOne(doc doc); );

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Extra: RX Driver

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ReactiveX

Observable Observer

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MongoDB Reactive Streams Driver

  • http://mongodb.github.io/mongo-java-driver-rx/
  • Observer based rather than callback based! (Cold Observables)
  • Built upon the MongoDB Async Driver & RxJava
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Join the Java Courses

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20

https://university.mongodb.com/courses/M101J

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Engineering Sales & Account Management Finance & People Operations Pre-Sales Engineering Marketing

Join the Team

View all jobs and apply: http://grnh.se/pj10su

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Obrigado!

Norberto Leite Technical Evangelist norberto@mongodb.com @nleite

https://github.com/nleite/java8demo

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A SIMPLE GUIDE TO USING AKKA PERSISTENCE

Joost Heijkoop

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WHAT WILL THIS BE ABOUT?

Using Akka with Scala Event Sourcing How to add Akka Persistence How to do Serialization with Stamina

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WHO AM I?

Joost Heijkoop I like to create/build/learn/share/teach stuff I'm a Software developer, Full Stack Developer, Back-end Developer, Consultant, ... I Work at Xebia Amsterdam.scala meetup (SUG) organisor Serial meetup / conference attendee

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BUILD STUFF!

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AKKA + SCALA

Akka is an Actor Framework, similar to Erlang Akka is message driven, "extreme" OO Scala hybrid programming language on the JVM

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AKKA + SCALA

class Parrot extends Actor { var count = 0

  • verride def receive: Receive = {

case message: String => { count = count + 1 println(s"$count: $message") } } } val parrot = system.actorOf(Parrot.props) parrot ! "Hello" parrot ! "Hello" 1: Hello 2: Hello

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WHAT IS EVENT SOURCING

All truths spring from recording events The current state is the sum of all events Command -> Event -> Update Recording of delta instead of current state You can replay all of history CQRS (Command Query Responsibility Segregation) - Martin Fowler

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EVENT SOURCING WITH AKKA PERSISTENCE

Get a command Create event Persist/record the event to Event Store Update the internal state

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EVENT SOURCING WITH AKKA PERSISTENCE

final def persist[A](event: A)(handler: (A) => Unit): Unit

  • verride def receiveCommand: Receive = {

case message: String => persist(Incremented(count + 1, message))(update) println(s"$count: $message") } def update: Receive = { case Incremented(newCount, message) => count = newCount }

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EVENT SOURCING WITH AKKA PERSISTENCE

class Parrot extends PersistentActor { var count = 0

  • verride def persistenceId = "parrot"
  • verride def receiveRecover: Receive =

{ case event: Incremented => update(event) }

  • verride def receiveCommand: Receive = {

case message: String => persist(Incremented(count + 1, message))(update) println(s"$count: $message") } def update = { case Incremented(newCount, message) => count = newCount } }

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AKKA + SCALA

class Parrot extends Actor { var count = 0

  • verride def receive: Receive = {

case message: String => { count = count + 1 println(s"$count: $message") } } }

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PERSISTED STATE

BEFORE

1: Hello 2: Hello [restart app] 1: Hello

WITH AKKA PERSISTENCE

1: Hello 2: Hello [restart app] 3: Hello

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STANDARD SERIALIZATION IS A PAIN

Java serialization is standard

Incremented(count: Int)

  • > IncrementedV2(count: Int, message: String)

What you want

Incremented(count: Int)

  • > Incremented(count: Int, message: String)
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STAMINA

It serializes to a non-binary format The default serialization is JSON Allows you to migrate before deserialization The is a catch, for now

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ADD STAMINA

SRC/MAIN/RESOURCES/APPLICATION.CONF

akka.actor { serializers { goto = "goto.PricingAkkaSerializer" } serialization-bindings { "stamina.Persistable" = goto } }

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ADD STAMINA

import stamina._ import stamina.json._ import stamina.json.SprayJsonMacros._ case class Incremented(count: Int) extends Persistable val parrotPersister = persister[Incremented]("increment") class PricingAkkaSerializer(persisters: Persisters) extends StaminaAkkaSerializer(persisters) { def this() { this(Persisters(List(Parrot.parrotPersister))) } }

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STAMINA MIGRATION

case class Incremented(count: Int, message: String) extends Persistable persist(Incremented(count + 1, message))(update) def update: Receive = { case Incremented(newCount, message) => count = newCount }

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STAMINA MIGRATION

import spray.json.lenses.JsonLenses._ val parrotPersister = persister[Incremented, V2]( "increment", from[V1].to[V2]( _.update('message ! set[String]("[empty message]"))) )

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STAMINA

PROJECT/BUILD.SCALA

import sbt.{Build, Project, ProjectRef, uri}

  • bject GotoBuild extends Build {

lazy val root = Project("root", sbt.file(".")) .dependsOn(staminaCore, staminaJson) lazy val staminaCore = ProjectRef( uri("git://github.com/scalapenos/stamina.git#master"), "stamina-core") lazy val staminaJson = ProjectRef( uri("git://github.com/scalapenos/stamina.git#master"), "stamina-json") }

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QUESTIONS

Using Akka with Scala? Event Sourcing? How to add Akka Persistence? How to do Serialization with Stamina? Wat?!?

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RESOURCES

Akka Persistence Stamina example Akka Persistence documentation Stamina - Akka Persistence serialization CQRS - Martin Fowler Event Sourcing - Martin Fowler Amsterdam.scala meetup group Xebia

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Design Design for Quality ality in in Java 8 a 8

Emil Forslund Speedment, Inc.

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About me

  • Emil Forslund
  • Code Monkey @ Speedment, Inc.
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About the project

Speedment is a java tool that

  • generates a domain model from a database,
  • rganize that model in a graph-like manner, and
  • let you write super-fast in-memory database transactions.
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About the project

Speedment has been in development for about 5 years and consist of roughly 1800 components. When Java 8 was released, the entire code base was rewritten to make use of all the new language features.

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Some words about inheritance

  • Created as a means of reducing code repetition almost 50 years ago
  • Makes it possible to organize code in a well established structure
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And what tends to happen?

  • As a system grows, dependency trees tend to grow as well
  • Often leads to coupled systems with bad maintainability
  • Testability worsens with complex inheritance models
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What is a trait?

  • A reusable component that can be combined to create classes
  • A description of a specific behavior or property
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Trait definition?

  • A set of methods that implement behavior
  • Stateless
  • Can be combined using the following operators:

–

Symmetric sum

–

Override (asymmetric sum)

–

Alias

–

Exclusion

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An example in Scala

trait HasName { def nameProperty() : Property[String] def setName(name : String) { nameProperty().set(name) } def getName(name : String) : Option[String] = nameProperty().get(name) }

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Traits in Java?

Was not possible... until recently with the release of Java 8

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Default methods

Using interface default methods, a concept similar to Traits can be achieved Interfaces can

  • be combined
  • be overridden
  • have a default implementation
  • be referenced using the ”&” selector
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What is the difference

Interfaces doesn't cover all the features of traits from other languages You still can’t:

  • prioritize different traits
  • do other operations than union
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So how does it look in Java?

interface HasName { Property<String> nameProperty(); default void setName(String name) { nameProperty().setValue(name); } default Optional<String> getName() { return Optional.ofNullable(nameProperty().getValue()); } }

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So how does it look in Java?

interface HasName { Property<String> nameProperty(); default void setName(String name) { nameProperty().setValue(name); } default Optional<String> getName() { return Optional.ofNullable(nameProperty().getValue()); } }

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So how does it look in Java?

interface HasName { Property<String> nameProperty(); default void setName(String name) { nameProperty().setValue(name); } default Optional<String> getName() { return Optional.ofNullable(nameProperty().getValue()); } }

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So how does it look in Java?

interface HasName { Property<String> nameProperty(); default void setName(String name) { nameProperty().setValue(name); } default Optional<String> getName() { return Optional.ofNullable(nameProperty().getValue()); } }

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Write decoupled systems

class Person implements HasName {...} class Pet implements HasName {...} class Friend { public void show(HasName a, HasName b) { System.out.println(a.getName().orElse("no one") + " is a friend of " + b.getName().orElse("no one") + "." ); } }

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Write decoupled systems

class Person implements HasName {...} class Pet implements HasName {...} class Friend { public void show(HasName a, HasName b) { System.out.println(a.getName().orElse("no one") + " is a friend of " + b.getName().orElse("no one") + "." ); } }

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Write decoupled systems

class Person implements HasName {...} class Pet implements HasName {...} class Friend { public void show(HasName a, HasName b) { System.out.println(a.getName().orElse("no one") + " is a friend of " + b.getName().orElse("no one") + "." ); } }

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Write decoupled systems

class Person implements HasName {...} class Pet implements HasName {...} class Friend { public void show(HasName a, HasName b) { System.out.println(a.getName().orElse("no one") + " is a friend of " + b.getName().orElse("no one") + "." ); } }

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Write decoupled systems

class Person implements HasName {...} class Pet implements HasName {...} class Friend { public void show(HasName a, HasName b) { System.out.println(a.getName().orElse("no one") + " is a friend of " + b.getName().orElse("no one") + "." ); } }

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Combine multiple traits

<T extends HasName & HasFields> String printFields(T obj) { return obj.getName() + " has the following fields: " + obj.getFields().collect(joining("\n")) ; }

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Combine multiple traits

<T extends HasName & HasFields> String printFields(T obj) { return obj.getName() + " has the following fields: " + obj.getFields().collect(joining("\n")) ; }

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Combine multiple traits

<T extends HasName & HasFields> String printFields(T obj) { return obj.getName() + " has the following fields: " + obj.getFields().collect(joining("\n")) ; }

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Combine multiple traits

<T extends HasName & HasFields> String printFields(T obj) { return obj.getName() + " has the following fields: " + obj.getFields().collect(joining("\n")) ; }

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Comparison

 More components to keep track of  More components to write tests for  Lower average file length  Easier to reuse code when scaling out functionality  Tests are more specific and might reveal more bugs

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Real world example

Refactoring Speedment took about 6 months Maintainability measurements improved by 70% Testability measurements improved by 40% Complexity was reduced by 90%

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Want to know more?

Interwebs: www.speedment.org Github: www.github.org/speedment Twitter: @Speedment @emifors