This is again a case where splitting client and server code into separate Maven modules will help (see https://github.com/tbroyer/gwt-maven-archetypes/). The problem here is (probably) that GWT tries to load the compiled classes, and can't because it doesn't understand Java 11 bytecode. So you'll want to compile the shared and client code to Java 8 bytecode, and the server-only code to Java 11 bytecode.
On Wednesday, July 17, 2019 at 10:56:58 AM UTC+2, Adrian Smith wrote: > > I understand that GWT 2.8.2 supports translation of Java 8 syntax, and not > Java 11. > > But I thought there might be a good chance that could use Java 11 features > on the server (e.g. Jetty) that responds to GWT-RPC requests. > > This works fine in deployment mode: Mark the project as Java 11 in Maven, > compile the WAR with Maven, GWT creates the JS fine, and then the Java 11 > servlet container executes the WAR fine, and the server code can make use > of Java 11 features. > > However in "super dev mode" it doesn't work, and also doesn't really give > an errors (neither on the console in Maven, nor in the "Jetty" tab of the > "super dev mode" console.) > > With a Java 11 JVM but specifying Java 8 in Maven (as is the default from > the Maven archtetype), everything works fine: > > $ java -version > openjdk version "11.0.2" 2019-01-15 > $ ~/Downloads/gwt-2.8.2/webAppCreator -templates maven,sample -out Foo > com.mycompany.Foo > > $ cd Foo > > $ mvn clean war:exploded gwt:devmode > > > That all works fine. > > However, when I change, in the pom.xml > > <maven.compiler.source>11</maven.compiler.source> > <maven.compiler.target>11</maven.compiler.target> > > > Then when I execute > > $ mvn clean war:exploded gwt:devmode > > > The "super dev mode" console opens, however when I click on "Launch > Default Browser" I see "503 Service Unavailable" in the browser. That error > message comes from Jetty. > > There is a note in the "Jetty" tab of the "super dev mode" console about > the 503 but just request/response headers and no further information. There > is also nothing printed to the terminal console where I executed the "mvn" > command. > > Note: I have not changed the source code at all. It's the default Maven > archetype source code, which doesn't use any Java 11 syntax. > > I have also tried changing the <sourceLevel>1.8</sourceLevel> in Maven's > GWT plugin section, however, as I expected, that failed immediately with a > clear error message that the GWT compiler doesn't support > 1.8, which is > fine. I know that's a lot of work, but I figured I could at least use Java > 11 features on the server. > > Am I missing something simple, or is this more complex than I imagine and > thus is not supported? > -- You received this message because you are subscribed to the Google Groups "GWT Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/google-web-toolkit/de2dc557-922d-4d43-bc30-32a7791da3fe%40googlegroups.com.
