Seems like GWT apps that use GIN will still require Java 8. I just tried
latest master from today using Guava 20-SNAPSHOT, Gin 2.1.2, Guice 4.
When we compile our app using JDK 1.7 and -sourceLevel 1.8 for GWT compiler
we get warnings for all java.util.function.* emulated classes that
reference java.lang.FunctionalInterface, e.g.
Resolving java.util.Objects
Found type 'java.util.Objects'
Resolving method requireNonNull
Found type 'java.util.function.Supplier'
[WARN] Ignoring unresolvable annotation type
java.lang.FunctionalInterface
Resolving java.util.Optional
Found type 'java.util.Optional'
Resolving method ifPresent
Found type 'java.util.function.Consumer'
[WARN] Ignoring unresolvable annotation type
java.lang.FunctionalInterface
Resolving method filter
Thats not really nice for a potential final release of GWT.
But the real issue is GIN as it fails with unsupported major.minor version
52.0:
Caused by: java.lang.UnsupportedClassVersionError:
xx/xx/xx/xx/SomeGinjector : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.lang.ClassLoader.defineClass(ClassLoader.java:643)
at
com.google.gwt.inject.rebind.GinBridgeClassLoader.findClass(GinBridgeClassLoader.java:160)
at
com.google.gwt.inject.rebind.GinBridgeClassLoader.loadClass(GinBridgeClassLoader.java:106)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:278)
at
com.google.gwt.inject.rebind.GinjectorGenerator.loadClass(GinjectorGenerator.java:223)
at
com.google.gwt.inject.rebind.GinjectorGenerator.getGinjectorType(GinjectorGenerator.java:104)
at
com.google.gwt.inject.rebind.GinjectorGenerator.generate(GinjectorGenerator.java:60)
at
com.google.gwt.core.ext.IncrementalGenerator.generateNonIncrementally(IncrementalGenerator.java:40)
at
com.google.gwt.dev.javac.StandardGeneratorContext.runGeneratorIncrementally(StandardGeneratorContext.java:745)
at
com.google.gwt.dev.cfg.RuleGenerateWith.realize(RuleGenerateWith.java:103)
at
com.google.gwt.dev.shell.StandardRebindOracle$Rebinder.rebind(StandardRebindOracle.java:78)
at
com.google.gwt.dev.shell.StandardRebindOracle.rebind(StandardRebindOracle.java:262)
at
com.google.gwt.dev.shell.StandardRebindOracle.rebind(StandardRebindOracle.java:251)
at
com.google.gwt.dev.PrecompilationContextCreator$1.getAllPossibleRebindAnswers(PrecompilationContextCreator.java:86)
Looks like GIN, executed with JDK 7, loads a class generated by JDT in
Java8 mode. Not sure if that can be fixed in GIN. For now we will use
master branch without the first Java 8 commits.
So I guess if we want GWT 2.8 to be fully JDK 7 compatible we have to
revert Java 8 commits and reintroduce -sourceLevel 1.7. However that would
mean we would need to release GWT 2.9 with Java 8 only support in a couple
of month at the time Guava 21 will be released (mid 2016, requires Java 8).
So I am not sure if its worth it to buy people a couple of extra month of
1.7 support.
Alternatively we could also make two releases 2.7.1 and 2.8 with 2.7.1
containing everything of 2.8 up until the first Java 8 commit. Then 2.7.1
will be Java 7 compatible and has lots of bug fixes while 2.8 is Java 8
only and contains only a couple more commits.
-- J.
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