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

[Adrian Smith]

Thanks Yuichi,

It turns out in the Super Dev Mode UI in the Jetty tab there was an error 
that Jetty couldn't start, and clicking on that showed me the stack 
backtrace in the bottom half of the window, and indeed it was some 
annotation processing problem with Jetty (common problem with older Jetty 
versions with Java 11).

Thanks to your blog post (translation worked nicely!) I did some 
investigation. I didn't get your method to work, but I did find out that if 
I all Maven (super dev mode) with the following command-line I can get my 
original single-Maven-project to use the Jetty of my choosing, and now 
Super Dev Mode can serve Java 11 server-side code:

mvn -Djetty.version=9.4.19.v20190610 war:exploded gwt:devmode 


Adrian
 
On Wednesday, July 17, 2019 at 11:31:37 AM UTC+2, Yuichi Sugimura wrote:
>
> 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 
> > 
> > 11 
> > 11 
> > 
> > 
> > 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 1.8 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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Re: Using Java 11 on the server to implement GWT-RPC services

[Adrian Smith]

Hello Thomas,

Thanks for the answer about splitting the Maven modules. That worked great!

In case anyone else is trying it, here's what I did:

   - Used the "mvn archetype:generate" from the 
   link https://github.com/tbroyer/gwt-maven-archetypes/ with the artifact 
   "modular-webapp"
   - In the root "pom.xml" upgraded the "jetty-maven-plugin" to the latest 
   version I found on Maven Central (I used "9.4.19.v20190610")
   - In the "server/pom.xml" added a plugin like

 
  maven-compiler-plugin
  
11
11
  


   - Followed the rest of the instructions to run the software from the 
   link above
   
This approach also has the advantage that the IDE understands that the 
"server" part is Java 11 but the "client" and "shared" sections are Java 8 
and can show appropriate syntax errors (e.g. usage of "var" keyword).

Thanks again,
Adrian

On Wednesday, July 17, 2019 at 11:12:26 AM UTC+2, Thomas Broyer wrote:
>
> 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
>>
>> 11
>> 11
>>
>>
>> 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 1.8 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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Re: Using Java 11 on the server to implement GWT-RPC services

[Yuichi Sugimura]

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

11
11


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

[Thomas Broyer]

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
>
> 11
> 11
>
>
> 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 1.8 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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