JVM Survival Guide. Hadi Hariri

Transcription

1 JVM Survival Guide Hadi Hariri

2 This talk For What For Who

3 20 years of Java The Sun and The Oracle Java The Language Java The Virtual Machine Java The Ecosystem

4 The Community Community Driven Not Vendor-Driven Large and Open Ecosystem

5 It s an Open Platform Languages Java, Clojure, Scala, Kotlin, Frege, Groovy, JRuby, Ceylon Frameworks JavaEE, Spring, Spark, Play Framework

6 What to Install Java SE Java EE Java FX JRE Java ME JDK

7 Versioning Language - 1.X where X is the version Java XY - X where X is the version Usually aligned major versioning in Language and VM

8 Installing Java Oracle Web Site (includes Ask Toolbar) Package Managers Brew, Chocolatey

9 JAVA_HOME Defines where Java Virtual Machine is located On Linux/OSX if undefined export JAVA_HOME=$(/usr/libexec/java_home)

10 Create a Java App Use javac to compile it Use java to run it Example - firstapp A First Java App

11 Decompiling example show byte code and also decompiling Decompiling

12 Multiple Classes and Files usingclass example

13 Java ARchives Archive classes files into single jar file Provide metadata with METAINF file jar command line to create jar files war is the web equivalent of jar

14 Creating Jar Files createjar.sh samples

15 Conventions In Java Virtual by default Open by default In other languages It depends

16 Conventions Packages and Modules Accessibility and Visibility Modifiers In Java, single class per file is enforced

17 Conventions Java and Java-inspired languages lowercamelcasenotation

18 Namespaces Or death by a hundred folders ext.vendor.module.subsystem Individual imports has been widely adopted

19 namespaces demo Namespaces

20 The Class Path Defines where Java Classes are located Set via command line java -cp Most common reason for NoClassDefFoundError

21 Class Loaders Responsible for loading classes Each class loader has a parent Delegates what it can to its parent

22 Class Loaders Parent Bootstrap Class Loader Parent Load java.lang and other key classes Extension Class Loader Parent Load java.ext.dirs System Class Loader Load classpath

23 Other Common Errors NoSuchMethodError - wrong version of class loaded ClassCastException - casting to wrong type IllegalAccessError - wrong access modifier

24 Using ClassPath usingclass Path example Compile and remove to show exception

25 Loading Classes loadingclasses Example

26 Build Systems Ant IntelliJ IDEA Eclipse

27 Build and Dependency Management Maven Gradle

28 Maven XML-Based Extensible Supports templates Maven Central Repository for Packages (and custom)

29 mavensample mavendependency mavenzip maventeamcity Maven

30 Gradle Not XML a.k.a. a better DSL Based on Groovy Extensible Somewhat template support (gradle --init) Maven Central Repository for Packages (and custom)

31 gradlesample sampleapp - app plugin Gradle

32 Working with Resources Resource folder to ship contents along with your app Ability to define in Maven/Gradle

33 Resources resourcessample resourcessamplemaven

34 Garbage Collection Generational (Young, Old, Permanent) The IDisposable is Closeable The using is try-with-resources

35 Asynchronous Programming CompletableFuture RxJava and adapters

36 Generics Most languages support Generics Reified Generics on JVM

37 Generics example of generics example of call site and covariance example of reflection

38 Testing Frameworks JUnit - The Standard TestNg Spek

39 junit junit from Java and Kotlin spek Testing

40 JavaEE The Dreaded Java 2 EE Glorious Enterprise Application Servers

41 Web Frameworks Servlets and Application Containers Jetty, TomCat

42 Spring

43 Spring Application Framework Web, Security, Templating, SQL, AWS, Social start.spring.io as generator

44 Spring springrestsample start.spring.io

45 Vert.x

46 Vert.x vertx example

47 Other Interesting Libraries Mockito for mocking GSon and Jackson for JSON Serialisation JodaTime for Calendar and Time Management Netty a low-level network client and server library

48 Summary Java is a very vibrant ecosystem Many languages, many frameworks There is no single vendor driven strategy as such

49 Thank - mail@hadihariri.com