Friday, February 18, 2022

Re: Building a GWT project in Eclipse 2019-03+ with Java 11.

Hi Jasper

I'll be just glad if my current progress saves someone's time.
I progress on step by step basis, so far I succeeded in Eclipse build and debugging.

Most of my problems were caused by combination of JDK11+ (namely modules) + Gradle + Eclipse + Eclipse GWT Plugin. 

Reason: GWT SDK gwt-dev.jar contains lot of classes that must not be visible to Eclipse compiler, but in fact they are, causing dreaded "The package org.w3c.dom is accessible from more than one module: <unnamed>, java.xml" error.
When `gradle build` is issued in command line the gwt-dev.jar from the maven repository is linked, it contains exactly essential google classes and nothing more. Thus the build succeeds.

But when you import such project in Eclipse under JDK11+ (I use JDK17) and select a GWT SDK there're lots of build errors caused by "The package is accessible from more than one module"

Reason: To run devmode or compilation server in Eclipse via Eclipse GWT plugin, you need full-blown gwt-dev.jar, so you need to install a GWT SDK and select it in your Eclipse project. And for some reason (by design of the Eclipse GWT plugin) this gwt-dev.jar from SDK spoils the Eclipse compilation classpath even if the build.gradle adds a dependency to the "essential" gwt-dev.jar

Indeed the Eclipse GWT Plugin allows to use an "essential" gwt-dev.jar from project dependencies instead of a real GWT SDK (even without installing it and registering in Eclipse), but only for Maven projects. Gradle is not covered. 

My solution was to patch an existing GWT SDK:

1. prepare GWT SDK 
assuming we have it installed into gwt-2.9.0 folder:
  mv gwt-2.9.0 gwt-2.9.0-jdk11
  cd gwt-2.9.0-jdk11

rename full blown gwt-dev 
  mv gwt-dev.jar gwt-dev-rundevserver-full.jar

 then assuming we already have dependencies stored in cache let's get the "essential" jar 
  cp ~/.m2/repository/com/google/gwt/gwt-dev/2.9.0/gwt-dev-2.9.0.jar gwt-dev.jar
 it will leak to Eclipse build classpath but it's jdk11-conformant (or rather Jigsaw conformant)

2. add the patched GWT SDK (its folder name gwt-2.9.0-jdk11 is used as its name) to Eclipse project via maven, so it will be already bound after project import
  
  eclipse.classpath {
    containers "com.gwtplugins.gwt.eclipse.core.GWT_CONTAINER/gwt-2.9.0-jdk11"
  }

3. Fix compilation server launcher

Let's refer the full-blown jar in launcher started by GWT Plugin:

Add a web server to eclipse (Tomcat or another one), 
add your webapp to the server (at this moment I usually set server start timeout to really long interval and uncheck the webapp "autoreloading enabled" to avoid webapp relaunch on hot code replace), 
then click "debug server" button:
  -> compilation server launcher config will be created, your webapp and the compilation server will launch but the latter will fail because the gwt-2.9.0-jdk11/gwt-dev.jar only contains skeleton files 
 
Stop the webapp
Edit the compilation server configuration: 
Edit classpath adding GWT_SDK_HOME/gwt-dev-rundevserver-full.jar as external jar to the [User entries] as the last entry:

image_2022-02-19_013438.png
 
"Debug server" once more: the compilation server must start and work now. The debugger and hot code replace for server classes will work as they should, and the changes to client java GWT files will be promptly recompiled when you refresh the page. It works in web server of your choice, not in Jetty bundled with GWT SDK. 
And click-through / debugging into XML/Servlet classes no more opens java bytecode in fullblown gwt-dev.jar but proper source files of JDK or your dependencies.

Hope this helps

Tequilacat

среда, 16 февраля 2022 г. в 06:12:23 UTC+1, blackh...@gmail.com:
Hi ,

You mention that you are migrating from jdk 1.8 to jdk 17.
We are in the same process, any tips you have?

regards,

Jasper

Op dinsdag 15 februari 2022 om 22:30:30 UTC+1 schreef tequil...@gmail.com:
Hi, 

> You're all set; the plugin will use the GWT dependencies from the Maven project.

The question - can I configure it with gradle?

I'm porting a GWT gradle-based Eclipse project from JDK 1.8 to JDK 17 (and from 2.8.2 to 2.9.0)
In Eclipse, there's typical JDK11+ error "The package org.xml.sax.helpers is accessible from more than one module" and it looks like the org.xml.sax classes shipped in gwt-dev.jar clash with jdk. Eclipse compiler somehow refers gwt-dev.jar. 
Command line gradle build succeeds OK.
If maven-central version of gwt-dev doesn't contain duplicating classes it would save the day. 

Is there a way to configure gradle project to force Eclipse plugin to use GWT version from gradle dependencies?

I have GWT 2.9.0 installed and added in Eclipse. To avoid referring this all-inclusive gwt-dev I removed GWT-2.9.0 from list of GWT SDKs in Eclipse settings, and now after importing/refreshing my gradle project the GWT plugin SDK selection doesn't contain 2.9.0 anymore even if I specify gradle dependency.

thank you

среда, 24 июля 2019 г. в 17:40:21 UTC+2, t.br...@gmail.com:


On Wednesday, July 24, 2019 at 5:14:42 PM UTC+2, Jim Douglas wrote:
> Sure. Use a build tool of your choice and use the maven dependencies. 

I don't know what that means. As far as I've ever known, developing a GWT application in Eclipse implies installing the GWT Plugin for Eclipse and picking a GWT SDK.


Nope.
Install the GWT Eclipse Plugin (https://gwt-plugins.github.io/documentation/gwt-eclipse-plugin/Download.html; note that the SDKs are optional).
You're all set; the plugin will use the GWT dependencies from the Maven project.

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