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Refactoring your code to Java 9 modules Rabea Gransberger (MEKO-S GmbH) @rgransberger

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Rabea Gransberger • Computer Science Diploma 2008 • Java Developer, Project Lead at MEKOS, Germany • Organization Team JUG Bremen, JavaLand, JCrete 03.10.2017 2 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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03.10.2017 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) 3 102: Process API Updates 110: HTTP 2 Client 143: Improve Contended Locking 158: Unified JVM Logging 165: Compiler Control 193: Variable Handles 197: Segmented Code Cache 199: Smart Java Compilation, Phase Two 200: The Modular JDK 201: Modular Source Code 211: Elide Deprecation Warnings on Import Statements 212: Resolve Lint and Doclint Warnings 213: Milling Project Coin 214: Remove GC Combinations Deprecated in JDK 8 215: Tiered Attribution for javac 216: Process Import Statements Correctly 217: Annotations Pipeline 2.0 219: Datagram Transport Layer Security (DTLS) 220: Modular Run-Time Images 221: Simplified Doclet API 222: jshell: The Java Shell (Read-Eval-Print Loop) 223: New Version-String Scheme 224: HTML5 Javadoc 225: Javadoc Search 226: UTF-8 Property Files 227: Unicode 7.0 228: Add More Diagnostic Commands 229: Create PKCS12 Keystores by Default 231: Remove Launch-Time JRE Version Selection 232: Improve Secure Application Performance 233: Generate Run-Time Compiler Tests Automatically 235: Test Class-File Attributes Generated by javac 236: Parser API for Nashorn 237: Linux/AArch64 Port 238: Multi-Release JAR Files 240: Remove the JVM TI hprof Agent 241: Remove the jhat Tool 243: Java-Level JVM Compiler Interface 244: TLS Application-Layer Protocol Negotiation Extension 245: Validate JVM Command-Line Flag Arguments 246: Leverage CPU Instructions for GHASH and RSA 247: Compile for Older Platform Versions 248: Make G1 the Default Garbage Collector 249: OCSP Stapling for TLS 250: Store Interned Strings in CDS Archives 251: Multi-Resolution Images 252: Use CLDR Locale Data by Default 253: Prepare JavaFX UI Controls & CSS APIs for Modularization 254: Compact Strings 255: Merge Selected Xerces 2.11.0 Updates into JAXP 256: BeanInfo Annotations 257: Update JavaFX/Media to Newer Version of GStreamer 258: HarfBuzz Font-Layout Engine 259: Stack-Walking API 260: Encapsulate Most Internal APIs 261: Module System 262: TIFF Image I/O 263: HiDPI Graphics on Windows and Linux 264: Platform Logging API and Service 265: Marlin Graphics Renderer 265: Marlin Graphics Renderer 266: More Concurrency Updates 267: Unicode 8.0 268: XML Catalogs 269: Convenience Factory Methods for Collections 270: Reserved Stack Areas for Critical Sections 271: Unified GC Logging 272: Platform-Specific Desktop Features 273: DRBG-Based SecureRandom Implementations 274: Enhanced Method Handles 275: Modular Java Application Packaging 276: Dynamic Linking of Language-Defined Object Models 277: Enhanced Deprecation 278: Additional Tests for Humongous Objects in G1 279: Improve Test-Failure Troubleshooting 280: Indify String Concatenation 281: HotSpot C++ Unit-Test Framework 282: jlink: The Java Linker 283: Enable GTK 3 on Linux 284: New HotSpot Build System 285: Spin-Wait Hints 287: SHA-3 Hash Algorithms 288: Disable SHA-1 Certificates 289: Deprecate the Applet API 290: Filter Incoming Serialization Data 292: Implement Selected ECMAScript 6 Features in Nashorn 294: Linux/s390x Port 295: Ahead-of-Time Compilation 297: Unified arm32/arm64 Port 298: Remove Demos and Samples

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03.10.2017 4 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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03.10.2017 5 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) Carola Lilienthal: It's all about the domain, honey!

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03.10.2017 6 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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03.10.2017 7 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) https://c2.staticflickr.com/4/3206 /2348940045_40482b7109_b.jpg

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Modules customer.service invoice.service picture.service camera.service 03.10.2017 8 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Java 8 Code • In Packages • In JARs • Classloader ignores Jars: No Dependency Graph • Linear Scan • More than one version of a class? 03.10.2017 9 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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OTIS • 155.159 LOC • 42.528 Classes • 3884 Packages • 285 Plugins (aka Modules) 03.10.2017 10 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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At the Vet 03.10.2017 11 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) Java 8 JavaFX Sample Application

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03.10.2017 12 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Entities 03.10.2017 13 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) Customer Pet Visit Invoice

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My friend … 03.10.2017 15 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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03.10.2017 16 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) Work Items Cars Brand Repair

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Vet Entities 03.10.2017 17 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) Customer Pet Visit Invoice

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Car Repair Entities 03.10.2017 18 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) Customer Pet Visit Invoice Car

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Identifiy Modules • Parts without cyclic dependencies • Tools • Structure 101 • Sonargraph • UML • jQAssistant • Degraph 03.10.2017 19 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) customer.service invoice.service

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1. Analysis 03.10.2017 20 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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03.10.2017 21 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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03.10.2017 22 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Domain Layers 03.10.2017 24 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) Customer Pet Visit Invoice

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Technical Layers 03.10.2017 25 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) Customer Pet Visit Invoice DB Model UI

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1. Refactoring: Technical Layers 03.10.2017 26 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) customer customer. model customer. db customer. ui

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Technical Layers 03.10.2017 27 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) Customer Pet Visit Invoice DB Model UI

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2. Analysis 03.10.2017 28 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Java 9 03.10.2017 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) 29

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Java 9 Platform Module System (JPMS) JSR 376: 25. Nov 2014 => Released 21.09.2017 • Reliable configuration: Replace Classpath (-Hell) • Strong encapsulation: public != Public • Scalable Java SE Platform (JEP 200: Modular JDK) • Greater platform integrity: illegal-access for internal API • Improved performance: No linear scans 03.10.2017 30 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Java 10 - Proposal • Release March 2018 as 18.3 • Feature Releases every half year: March / September • Update Releases: Jan, Apr, Jul, Oct • LTS Releases every 3 years from Sep 2018 • Code moves to OpenJDK • Mission Control and FlightRecorder Open Sourced • JEE => EE4J at Eclipse Foundation • https://mreinhold.org/blog/forward-faster • https://blogs.oracle.com/java-platform-group/faster-and-easier-use-and-redistribution-of-java-se 03.10.2017 31 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Java 9 Module Definition src\module-info.java module { requires ; exports ; uses ; provides with ; } 03.10.2017 32 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Module 03.10.2017 33 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) model ui db util requires module model { exports db; } module ui { requires model; exports table; } table CustomerTable Customer getCustomer()

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03.10.2017 34 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) model ui db util table requires module model { exports db; } module ui { requires model; exports table; } Module

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03.10.2017 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) 35 Customer Pet Visit Invoice Car

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New Modules 03.10.2017 36 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) model customer.model visit.model invoice.model ui customer.ui visit.ui invoice.ui pet pet.model pet.db pet.ui vet ui

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2. Refactoring: Create Modules 03.10.2017 37 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) • Warning: No Split-Packages allowed model customer ui customer

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Demo 03.10.2017 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) 38

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03.10.2017 39 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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CustomerView private Node createTabPane() { TabPane tabPane = new TabPane(); tabPane.getTabs().add(createTab("Pets", createPetNode())); tabPane.getTabs().add(createTab("Invoices", createInvoiceNode())); return tabPane; } private Node createPetNode() { List pets = new PetDao().fetchPetsForCustomer(customer.getId()); PetTable table = new PetTable(pets, false) { protected void onDoubleClick(Pet pet) { replace(new PetView(customer, pet)); } }; return table; } 03.10.2017 40 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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3. Refactoring: Resolve Dependencies 03.10.2017 41 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) ui CustomerView TabService List createTabs() pet PetTabService List createTabs() PetTable module ui { exports service; uses CustomerViewTabService; } module pet { requires ui; provides CustomerViewTabService with PetCustomerViewTabService; } Service Loader

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Demo 03.10.2017 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) 42

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4. Refactoring: Car Repair Shop • de.rgra.car replaces de.rgra.pet • de.rgra.vet.ui transformed to de.rgra.app • New Service: ApplicationConfigurationProvider • New: de.rgra.vet.app and de.rgra.car.app • Implement ApplicationConfigurationProvider 03.10.2017 43 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Demo 03.10.2017 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) 44

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Jigsaw Dependency Visualizer 03.10.2017 46 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Deployment 03.10.2017 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) 47

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Compile • %JAVA_9%\javac --module-path mods --module-source-path "./*/src" -d classes -Xlint:exports @sources.txt • %JAVA_9%\jar --create --file mlib/vet/de.rgra.model.jar -C mods/vet/de.rgra.model_05 . 03.10.2017 48 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Compile • dir /s /B *.java | find "." > sources.txt • %JAVA_9%\javac -p mods --module-source-path "./*/src" -d classes @sources.txt • xcopy /s/Y "de.rgra.model_05/resources" "classes/de.rgra.model_05" • %JAVA_9%\jar --create --file mlib/vet/de.rgra.model.jar -C classes/de.rgra.model_05 . 03.10.2017 49 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Run • %JAVA_9%\java -p mods/vet -m de.rgra.vet.app_05/de.rgra.vet.VetAppConfiguration 03.10.2017 50 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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JLink • %JAVA_9%/jlink --module-path %JAVA_9%\jmods;mlib;mlib/vet --add-modules de.rgra.vet.app_05 --output vetapp --launcher vet=de.rgra.vet.app_05/de.rgra.vet.VetAppConfiguration • run vetapp/bin/vet.bat 03.10.2017 51 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Summary 03.10.2017 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) 52

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jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) 03.10.2017 54

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Refactoring Steps • Package Structure: .. . .. • Domain Drive Design • Design Patterns 1. Analyse dependencies 2. Identifiy / Create Modules 3. Move Code to new modules 4. Resolve Dependencies with Interfaces / Services 5. Go to 1. 03.10.2017 55 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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03.10.2017 56 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger) https://i.ytimg.com/vi/RijScDMVQzQ/maxresdefault.jpg "The only thing a big bang rewrite guarantees is a Big Bang!" (M. Fowler)

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OTIS • New module on business need • new customer • new service provider • From monolith to 283 plugins in 5 years • Think about module boundaries • Refactoring usually easy by using new interfaces 03.10.2017 57 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Advantages: Module vs. Monolith • Architecture reflected in modules with clear boundaries • Hide public classes • Replace single modules • Module Path more robust than Classpath • Runtime Errors (NoClassDefFoundError) detected at startup, not after x hours • Jar Hell: 2 versions of Jars in Classpath • Tool Support: Which Dependencies are missing? • Smaller deployable units • Better (Startup-) Performance 03.10.2017 58 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)

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Q & A Slides & Code: https://rgra.github.io Twitter: @rgransberger 03.10.2017 59 jDD Krakow / Java 9 Refactoring (Rabea Gransberger @rgransberger)