Supporting Java™ 9 in Eclipse - A critical perspective - Stephan Herrmann
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The document discusses supporting Java 9 in Eclipse through 4 acts. Act 1 introduces Java modules and demonstrates them in Eclipse. Act 2 discusses issues with existing Eclipse APIs due to Java 9 changes. Act 3 explores complexities around split packages and package references between modules. Act 4 discusses representing Java 9 module options in the Eclipse UI. The conclusion reflects on encapsulation, isolation and compatibility challenges with Java 9.
![8
J
D
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Stephan Herrmann @Eclipse Day India 2018 – published under the EPL
Act 2: Something's weird
JDT API (1):
org.eclipse.jdt.core.ToolFactory.createScanner(..)
org.eclipse.jdt.core.compiler.IScanner
●
void resetTo(int startPosition, int endPosition)
●
int getNextToken()
org.eclipse.jdt.core.compiler.ITerminalSymbols.TokenNameIdentifer
In Java 9 this API is beyond repair
restricted keywords:
●
“keywords that are keywords when they are keywords, else identifers” [my words]
●
classifcation keyword / identifer happens after parsing
should we remove this API (and break all clients of JDT)?
just hope that nobody will use it for module-info.java?](https://image.slidesharecdn.com/java9edi2018-180924095500/85/Supporting-Java-9-in-Eclipse-A-critical-perspective-Stephan-Herrmann-7-320.jpg)
![9
J
D
T
Stephan Herrmann @Eclipse Day India 2018 – published under the EPL
Act 2: Something's weird
JDT API (1):
org.eclipse.jdt.core.ToolFactory.createScanner(..)
org.eclipse.jdt.core.compiler.IScanner
●
void resetTo(int startPosition, int endPosition)
●
int getNextToken()
org.eclipse.jdt.core.compiler.ITerminalSymbols.TokenNameIdentifer
In Java 9 this API is beyond repair
restricted keywords:
●
“keywords that are keywords when they are keywords, else identifers” [my words]
●
classifcation keyword / identifer happens after parsing
should we remove this API (and break all clients of JDT)?
just hope that nobody will use it for module-info.java?
import to.uses;
import to.module;
import to.to;
module module {
requires requires;
exports to to exports;
uses module;
provides uses with to;
requires transitive transitive;
}
import to.uses;
import to.module;
import to.to;
module module {
requires requires;
exports to to exports;
uses module;
provides uses with to;
requires transitive transitive;
}](https://image.slidesharecdn.com/java9edi2018-180924095500/85/Supporting-Java-9-in-Eclipse-A-critical-perspective-Stephan-Herrmann-8-320.jpg)
![37
J
D
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Stephan Herrmann @Eclipse Day India 2018 – published under the EPL
Epilogue
Act 4: Modifying Encapsulation?
“Gradual Encapsulation” [Herrmann 2008]
●
is encapsulation your friend or foe?
●
enforce encapsulation?
●
rules entail exceptions
Act 3: Isolation?
Separate namespace per module?
●
partly achieved / emulated
●
several opportunities missed
Act 2: Compatibility?
Java 9 is disruptive
●
against frameworks and applications
●
against tools](https://image.slidesharecdn.com/java9edi2018-180924095500/85/Supporting-Java-9-in-Eclipse-A-critical-perspective-Stephan-Herrmann-31-320.jpg)
![38
J
D
T
Stephan Herrmann @Eclipse Day India 2018 – published under the EPL
Epilogue
Act 4: Modifying Encapsulation?
“Gradual Encapsulation” [Herrmann 2008]
●
is encapsulation your friend or foe?
●
enforce encapsulation?
●
rules entail exceptions
Act 3: Isolation?
Separate namespace per module?
●
partly achieved / emulated
●
several opportunities missed
Act 2: Compatibility?
Java 9 is disruptive
●
against frameworks and applications
●
against tools
@NonNullByDefault
module org.eclipse.mymodule {
…
}
@NonNullByDefault
module org.eclipse.mymodule {
…
}](https://image.slidesharecdn.com/java9edi2018-180924095500/85/Supporting-Java-9-in-Eclipse-A-critical-perspective-Stephan-Herrmann-32-320.jpg)
Supporting Java™ 9 in Eclipse - A critical perspective - Stephan Herrmann
- 1. Stephan Herrmann Supporting Java™ 9 in Eclipse — A critical perspective J D T Simply Retail.
- 2. 2 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Supporting Java™ 9 in Eclipse A Play in 4 Acts
- 3. 3 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 1 What is Jigsaw all about? That's simple and easy!That's simple and easy!
- 4. 4 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Simple: Module Syntax vs. OSGi Manifest module org.m1 { … requires org.m2; requires transitive org.m3; exports org.pack1; exports org.pack2 to org.m2; provides org.Ifc with org.Impl; uses org.Ifc; Bundle-SymbolicName: org.m1 Require-Bundle: org.m2 org.m3;visibility:=reexport Export-Package: org.pack1 org.pack2;x-friends=”org.m2” service.xml module-info.java MANIFEST.MF <scr:component xmlns:scr="http://www.osgi.org/xmlns/scr/v1.1.0" name="IMyService"> <implementation class="org.Impl"/> <service> <provide interface="org.Ifc"/> </service> </scr:component>
- 5. 5 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 1: That's simple and easy! DEMO: Modules in Eclipse
- 6. 6 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 2 A closer look at module-info – from a tool smith's perspective Expect a slight sense of surprise Expect a slight sense of surprise
- 7. 8 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 2: Something's weird JDT API (1): org.eclipse.jdt.core.ToolFactory.createScanner(..) org.eclipse.jdt.core.compiler.IScanner ● void resetTo(int startPosition, int endPosition) ● int getNextToken() org.eclipse.jdt.core.compiler.ITerminalSymbols.TokenNameIdentifer In Java 9 this API is beyond repair restricted keywords: ● “keywords that are keywords when they are keywords, else identifers” [my words] ● classifcation keyword / identifer happens after parsing should we remove this API (and break all clients of JDT)? just hope that nobody will use it for module-info.java?
- 8. 9 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 2: Something's weird JDT API (1): org.eclipse.jdt.core.ToolFactory.createScanner(..) org.eclipse.jdt.core.compiler.IScanner ● void resetTo(int startPosition, int endPosition) ● int getNextToken() org.eclipse.jdt.core.compiler.ITerminalSymbols.TokenNameIdentifer In Java 9 this API is beyond repair restricted keywords: ● “keywords that are keywords when they are keywords, else identifers” [my words] ● classifcation keyword / identifer happens after parsing should we remove this API (and break all clients of JDT)? just hope that nobody will use it for module-info.java? import to.uses; import to.module; import to.to; module module { requires requires; exports to to exports; uses module; provides uses with to; requires transitive transitive; } import to.uses; import to.module; import to.to; module module { requires requires; exports to to exports; uses module; provides uses with to; requires transitive transitive; }
- 9. 11 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 2: Something's weird Updating Tools Java™ 8 Java→ ™ 9 cannot be done in a compatible way
- 10. 12 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3 There is complexity — Questions: What is the meaning of a.b.C1? Is the reference a.b.C1 legal? Does Java 9 support split packages?
- 11. 14 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: Concepts How we want to see the world: Module 1 package a C1 C2C0 package a.b C1 C3 Module 2 package a.c C1 C2 package a.b C1 C4 requires
- 12. 15 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: Realization This is the world according to JLS: Module 1 Module 2 C1 CU1 C0 associated with CU2 C2 package a declares package bis member within CU1 C1 CU1 C1 package c CU2 C2 requires exports
- 13. 16 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: unnecessary complexity Containment module package class Independent packages among each other Module 1 package a C1 C2C0 package a.b C1 C3 Module 2 package a.c C1 C2 package a.b C1 C4 requires Emulation by indirect relations cu is associated to module cu declares package cu contains class Containment package sub-package Mod- ule 1 Mod- ule 2C1 C0 CU1 C2 CU2 package a package b C1 CU1 CU1 C1 package c C2 CU2 requires
- 14. 17 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: Putting it to work Inside Module2, what does a.b.C1 mean? a.b.C1 is found in the CU1 associated with Module2 package a.b is uniquely visible from Module2 Module 1 Module 2 C1 CU1 C0CU2 C2 package a package b CU1 C1 CU1 C1 package c CU2 C2 requires package b ✔ ✔ package a
- 15. 18 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: Putting it to work Inside Module2, what does a.b.C1 mean? package a.b is not uniquely visible, could be from Module1 or from Module2 this confguration is illegal Module 1 Module 2 C1 CU1 C0CU2 C2 package a package b CU1 C1 CU1 C1 package c CU2 C2 requires CUX X
- 16. 19 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: Legal but broken Module 1 Module 2 C1 CU1 C0CU2 C2 package a package b CU1 C1 CU1 C1 package c CU2 C2 requires $ java -m Module2 Error occurred during initialization of boot layer java.lang.LayerInstantiationException: Package a.b in both module Module1 and module Module2 $ _ Need a Layer implementation that is capable of classloader-based isolation. Need a Layer implementation that is capable of classloader-based isolation.
- 17. 20 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: Legal but asking for trouble API Leak API mentions a type, which the client cannot mention legal new complexity in the implementation put overloading and inheritance in the mix: infnite supply of new Java puzzlers Module 1 Module 2 C1 CU1 C0CU2 C2 package a package b CU1 C1 CU1 C1 package c CU2 C2 requires public void doSomething(a.b.C1 arg) { … }public void doSomething(a.b.C1 arg) { … }
- 18. 21 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: Legal but asking for trouble API Leak API mentions a type, which the client cannot mention legal new complexity in the implementation put overloading and inheritance in the mix: infnite supply of new Java puzzlers Module 1 Module 2 C1 CU1 C0CU2 C2 package a package b CU1 C1 CU1 C1 package c CU2 C2 requires public void doSomething(a.b.C1 arg) { … }public void doSomething(a.b.C1 arg) { … } Missed Opportunity ● API leaks should be illegal ● Or method should be unmentionable for clients Missed Opportunity ● API leaks should be illegal ● Or method should be unmentionable for clients
- 19. 22 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: summary encapsulation Split packages concealed: legal ● but no promise that the runtime can handle it ● need a capable Layer implementation merging a package (like fragment & host bundle) is illegal ● even if no class-level confict is involved API leaks JLS is silent compilers issue warnings ● TODO: better coordinate warnings between compilers
- 20. 25 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 3: There is Complexity End of Act 3 A simple surface realized by complexity
- 21. 26 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4 There's a lot more: command line options –illegal-access={permit,warn,debug,deny}
- 22. 28 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4: Manipulating the Module Graph Things you can change via CLI options Add / remove / replace a module Add a “reads” edge (“requires”) Expose a package ● compile time (“exports”) ● runtime (“opens”) Merge a module from several sources ● patching ...
- 23. 29 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4: Options Let's map command line options to UI
- 24. 30 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4: Options “Is modular” Edit: enter the rabbit hole
- 25. 31 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4: Options “Is modular” Edit: enter the rabbit hole Contents what you ask for what you get --limit-modules, --add-modules default as per JEP 261
- 26. 32 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4: Options “Is modular” Edit: enter the rabbit hole Contents what you ask for what you get --limit-modules, --add-modules default as per JEP 261 Details --add-exports --add-reads (rarely needed) --patch-module (careful!)
- 27. 33 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4: Options “Is modular” Edit: enter the rabbit hole Contents what you ask for what you get --limit-modules, --add-modules default as per JEP 261 Details --add-exports --add-reads (rarely needed) --patch-module (careful!) Power switch
- 28. 34 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4: Options Build vs. Run UI should be sufcient for building ● No need to learn cryptic CLI Sufcient information for running? Show Command Line New in 2018-09
- 29. 35 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4: Options Build vs. Run UI should be sufcient for building ● No need to learn cryptic CLI Sufcient information for running? Show Command Line New in 2018-09 Override Dependencies New in Photon
- 30. 36 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Act 4: Options Build vs. Run UI should be sufcient for building ● No need to learn cryptic CLI Sufcient information for running? Show Command Line New in 2018-09 Override Dependencies New in Photon More UI … work in progress ...
- 31. 37 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Epilogue Act 4: Modifying Encapsulation? “Gradual Encapsulation” [Herrmann 2008] ● is encapsulation your friend or foe? ● enforce encapsulation? ● rules entail exceptions Act 3: Isolation? Separate namespace per module? ● partly achieved / emulated ● several opportunities missed Act 2: Compatibility? Java 9 is disruptive ● against frameworks and applications ● against tools
- 32. 38 J D T Stephan Herrmann @Eclipse Day India 2018 – published under the EPL Epilogue Act 4: Modifying Encapsulation? “Gradual Encapsulation” [Herrmann 2008] ● is encapsulation your friend or foe? ● enforce encapsulation? ● rules entail exceptions Act 3: Isolation? Separate namespace per module? ● partly achieved / emulated ● several opportunities missed Act 2: Compatibility? Java 9 is disruptive ● against frameworks and applications ● against tools @NonNullByDefault module org.eclipse.mymodule { … } @NonNullByDefault module org.eclipse.mymodule { … }