Re: Using Java 11 on the server to implement GWT-RPC services

Hello, I've got the very same situation but in the different environment.

I think perhaps it is because old version of jetty(9.2) is embedded in
gwt-dev.jar(2.3.2). This version of jetty doesn't seem to run on Java9
or later.

So you should exclude org.eclipse.jetty package from gwt-dev.jar and
attach newer version of jetty to classpath.

Here's my blog post(in Japanese) about this. Maybe you can use some
translation site.

https://www.gwtcenter.com/execute-gwt282-on-java9-or-later

Hope this helps.

On 2019/07/17 17:51, 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?
>
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