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Migrating to Java 9 Modules
- 1. By Sander Mak Migrating to Java 9 Modules @Sander_Mak
- 2. Migrating to Java 9 java -cp .. -jar myapp.jarJava 8
- 3. Migrating to Java 9 java -cp .. -jar myapp.jar java -cp .. -jar myapp.jar Java 8 Java 9
- 6. Today's journey Running on Java 9 Java 9 modules Migrating to modules Modularising code
- 7. Migrating to Java 9 Let's try it! java -cp .. -jar myapp.jar java -cp .. -jar myapp.jar Java 8 Java 9
- 8. Classpath migration problems ‣ Unresolved platform modules ‣ (Ab)use of platform internals
- 9. Missing platform modules error: package javax.xml.bind does not exist import javax.xml.bind.DatatypeConverter; public class Main { public static void main(String... args) { DatatypeConverter.parseBase64Binary("SGVsbG8gd29ybGQh"); } }
- 10. Modular JDK
- 11. Modular JDK
- 12. Modular JDK
- 13. Modular JDK
- 14. Modular JDK
- 15. ‣ Classpath compile-time “java.se” module is used ‣ This does not resolve: java.activation java.corba java.transaction java.xml.bind java.xml.ws java.xml.ws.annotation Missing platform modules
- 16. Add unresolved platform modules jdeps demo/Main.class Main.class -> java.base Main.class -> not found <unnamed> -> java.lang java.base <unnamed> -> javax.xml.bind not found Find
- 17. javac --add-modules java.xml.bind demo/Main.java Add unresolved platform modules jdeps demo/Main.class Main.class -> java.base Main.class -> not found <unnamed> -> java.lang java.base <unnamed> -> javax.xml.bind not found Find Fix
- 18. javac --add-modules java.xml.bind demo/Main.java Add unresolved platform modules java --add-modules java.xml.bind demo/Main.java jdeps demo/Main.class Main.class -> java.base Main.class -> not found <unnamed> -> java.lang java.base <unnamed> -> javax.xml.bind not found Find Fix
- 19. javac --add-modules java.xml.bind demo/Main.java Add unresolved platform modules java --add-modules java.xml.bind demo/Main.java Let's try it!
- 20. public class Main { public static void main(String... args) throws Exception { sun.security.x509.X500Name name = new sun.security.x509.X500Name("CN=user"); } } Using encapsulated APIs
- 21. public class Main { public static void main(String... args) throws Exception { sun.security.x509.X500Name name = new sun.security.x509.X500Name("CN=user"); } } Using encapsulated APIs Main.java:4: error: package sun.security.x509 does not exist sun.security.x509.X500Name name = ^
- 22. jdeps -jdkinternals Main.class Main.class -> java.base Main -> sun.security.x509.X500Name JDK internal API (java.base) JDK Internal API Suggested Replacement ---------------- --------------------- sun.security.x509.X500Name Use javax.security.auth.x500.X500Principal @since 1.4 Use jdeps to find problems
- 23. Using encapsulated APIs Compile with 1.8, run with 9:
- 24. Using encapsulated APIs Exception in thread "main" java.lang.IllegalAccessError: class Main (in unnamed module @0x4cdbe50f) cannot access class sun.security.x509.X500Name (in module java.base) because module java.base does not export sun.security.x509 to unnamed module @0x4cdbe50f at Main.main(Main.java:4) Compile with 1.8, run with 9:
- 25. Using encapsulated APIs java --add-exports java.base/sun.security.x509=ALL-UNNAMED Main Exception in thread "main" java.lang.IllegalAccessError: class Main (in unnamed module @0x4cdbe50f) cannot access class sun.security.x509.X500Name (in module java.base) because module java.base does not export sun.security.x509 to unnamed module @0x4cdbe50f at Main.main(Main.java:4) Compile with 1.8, run with 9:
- 26. Using encapsulated APIs Exception in thread "main" java.lang.IllegalAccessError: class Main (in unnamed module @0x4cdbe50f) cannot access class sun.security.x509.X500Name (in module java.base) because module java.base does not export sun.security.x509 to unnamed module @0x4cdbe50f at Main.main(Main.java:4) Compile with 1.8, run with 9: java --permit-illegal-access Main New 'kill-switch':
- 29. Actual view of your app
- 30. main books.api books.impl bookstore Java 9 modules make this possible!
- 32. Top down migration commons.lang3.3.4.jar demonstrator.jar classpath java.base module path
- 33. package com.javamodularity.demonstrator; import org.apache.commons.lang3.StringUtils; public class Demo { public static void main(String args[]) { String output = StringUtils.leftPad("Leftpad FTW!", 20); System.out.println(output); } } Classic classpath
- 34. package com.javamodularity.demonstrator; import org.apache.commons.lang3.StringUtils; public class Demo { public static void main(String args[]) { String output = StringUtils.leftPad("Leftpad FTW!", 20); System.out.println(output); } } Classic classpath javac -cp lib/commons-lang3-3.4.jar -d out $(find src -name '*.java') java -cp out:lib/commons-lang3-3.4.jar com.javamodularity.demonstrator.Demo Compile Run
- 35. Top down migration commons.lang3.3.4.jar demonstrator.jar classpath java.base module path
- 36. Top down migration commons.lang3.3.4.jar demonstrator.jar classpath java.base module path Can’t reference the classpath from named modules!
- 37. Top down migration demonstrator.jar classpath java.base module path commons.lang But this isn’t our code!
- 38. Automatic Modules ‣ A plain JAR on the module path becomes an Automatic Module ‣ Module name derived from JAR name ‣ Exports everything ‣ Reads all other modules
- 39. module demonstrator { requires commons.lang; } Using Automatic Modules
- 40. module demonstrator { requires commons.lang; } Using Automatic Modules javac --module-path lib --module-source-path src -d mods $(find src -name '*.java') java --module-path mods:lib -m demonstrator/com.javamodularity.demonstrator.Demo Compile Run
- 41. Migrating the books app 1. Create a “monolith module” 2. Declare exports 3. Figure out “requires” 4. Move some libs to Automatic Modules Step 2
- 42. commons.pool spring.context classpath Application code module path spring.tx hibernate.core hibernate.jpa javax.inject Automatic modules Named modules commons.logging spring.beans spring.aop spring.core hsqldb spring.orm …
- 43. commons.pool spring.context classpath Application code module path spring.tx hibernate.core hibernate.jpa javax.inject Automatic modules Named modules commons.logging spring.beans spring.aop spring.core hsqldb spring.orm …
- 44. DEMO
- 45. Open Modules ‣ Reliable configuration like normal modules ‣ Requires for every dependency ‣ Opens all packages for deep reflection ‣ Easy compatibility with existing code and frameworks ‣ Allows reflection
- 46. Type Compile time Reflection on public Deep reflection Exports ✓ ✓ ✘ Open ✘ ✓ ✓ Exports + Open ✓ ✓ ✓
- 47. Open Packages Opens the package for deep reflection, but not compile time access A package can be both open and exported
- 48. Tip 1 Move libraries to module path one by one Start with direct dependencies
- 49. Tip 2 open when no compile time dependency should exist (possibly qualified)
- 50. Tip 3 requires only for direct dependencies --add-modules for run-time dependencies
- 51. Tip 4 Use open modules for framework compatibility Fine tune open later
- 52. Migrating the books app 1. Split monolith module 2. Move requires/exports 3. (optional) Move config files Step 3
- 53. commons.pool spring.context classpath Application code module path spring.tx hibernate.core hibernate.jpa javax.inject Automatic modules Named modules commons.logging spring.beans spring.aop spring.core hsqldb spring.orm …
- 54. commons.pool spring.context classpath module path spring.tx hibernate.core hibernate.jpa javax.inject Automatic modules Named modules commons.logging spring.beans spring.aop spring.core hsqldb spring.orm … main books.api books.impl bookstore
- 55. Migration steps - recap
- 56. Migration steps - recap ‣ Migrate to Java 9 using classpath only
- 57. Migration steps - recap ‣ Migrate to Java 9 using classpath only ‣ Create a module around your whole app
- 58. Migration steps - recap ‣ Migrate to Java 9 using classpath only ‣ Create a module around your whole app ‣ Modularize your application!
- 59. Thank you. bit.ly/java9book @javamodularity code @ bit.ly/java9mig
- 60. Thank you. bit.ly/java9book @javamodularity http://bit.ly/java9course Java 9 Modularity: First Look code @ bit.ly/java9mig