is it possible to debug GWT projects (breakpoints, step through code etc) ?

[Daniel Webb]

Hi, 

Is it possible to debug GWT projects - setting breakpoints and stepping through code? This would be server and/or client debugging.

We've just had our internal GWT based app updated and it now uses maven to run (clean install appengine:run). The eclipse plugin based debugging technique that I used to use no longer seems to work.

Thanks for any advice, I really like GWT but I'm lost as to how it all works!

Daniel

[Jens]

Debugging server code is done as usual using Java debug wire protocol (JDWP) remote debugging.

Debugging client code is done using the browser dev tools which also allows setting breakpoints. During development GWT CodeServer should be started using '-style PRETTY -XmethodNameDisplayMode ABBREVIATED' which makes JS readable (but not super detailed) in case you do not want to use SourceMaps.

-- J.

[Daniel Webb]

Thanks Jens, I appreciate the answer, gives me something to have a go at.

Regards

Daniel.

[Ralph Fiergolla]

Hi! Unless you want to invest time and effort in getting eclipse plugins up and running, I would suggest using your browser's development tools (Ctrl+Shift+I in Chrome/Edge) to debug the client side. Thanks to source maps it will show your JAVA source code when debugging. 

To debug the server side, you need to start your server with "-Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=8000,suspend=n" and create a debug configuration to connect to port 8000 in Eclipse.

Good luck

Ralph

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[Craig Mitchell]

As Ralph says, for the client, you can use the Chrome debugger, but if you didn't want to, the Eclipse SDBG plugin should still work.  Or if you use IntelliJ, the paid Ultimate version comes with a JS debuger (I've not seen a JS debugger for the free Community version).

For the server, you might find it easier to put the flags Ralph talks about into your pom file.  Eg: If you use springboot, you can do this:

<plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
  <executions>
    <execution>
      <goals>
        <goal>repackage</goal>
      </goals>
    </execution>
  </executions>
  <configuration>
    <skip>false</skip>
    <jvmArguments>
      -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:8000 <!-- Allow debugging -->
      --add-opens java.base/java.lang=ALL-UNNAMED <!-- Allow exceptions to have java.lang details serialised -->
    </jvmArguments>
  </configuration>
</plugin>

[Craig Mitchell]

btw:  "appengine:run" is deprecated.  You won't be able to do any updates to your app until you upgrade.  https://cloud.google.com/appengine/docs/legacy/standard/java/maven-reference  But you probably already knew this.  🙂

[Daniel Webb]

Thanks Ralph, So it's source map debugging in chrome for the client side, jdwp remote debugging for the server side.

[Daniel Webb]

Hi Craig,

On Wednesday 26 June 2024 at 02:56:31 UTC+1 Craig Mitchell wrote:

btw:  "appengine:run" is deprecated.  You won't be able to do any updates to your app until you upgrade.  https://cloud.google.com/appengine/docs/legacy/standard/java/maven-reference  But you probably already knew this.  🙂

Whaat, are you sure?! 

Only reason I ask is I've just had the app updated from java 7 because Google dropped support - and the new project uses "appengine:run" for running locally. Should we be doing it differently?

[Daniel Webb]

Hi,

Can anyone help me get remote jdwp server debugging in Eclipse working? I seem to be able to get a server running but it won't halt on breakpoints.

I run as.. "Maven Build" with goals of 'clean install appengine:run' and vm arguments of '-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000'

The Console says "Listening for transport dt_socket at address: 8000"

Then I "Debug as..." "Remote Java Application"...

And the console starts up again with the 'clean install appengine:run' finishing up with the usual:

Started NetworkTrafficSelectChannelConnector {HTTP/1.1, (http/1.1)}{localhost:8080}

At which point I can browse to http://localhost:8080 but none of my breakpoints will trigger.

Please, what am I doing wrong? I've not done java remote debugging before :-(

Regards

Daniel

[Tim Macpherson]

Did you open the debug view ? iirc in eclipse you need to

Yahoo Mail: Search, Organize, Conquer

On Thu, Jun 27, 2024 at 6:15 PM, 'Daniel Webb' via GWT Users

<google-we...@googlegroups.com> wrote:

https://groups.google.com/d/msgid/google-web-toolkit/66677696-106b-42ff-bea4-15bd6984b19an%40googlegroups.com

.

[Craig Mitchell]

> Only reason I ask is I've just had the app updated from java 7 because Google dropped support - and the new project uses "appengine:run" for running locally. Should we be doing it differently?

Google are asking everyone to move to the "Second-generation Java runtimes".  https://cloud.google.com/appengine/migration-center/standard/migrate-to-second-gen/java-differences

This also includes upgrading some services, which can be a big task.  I needed to upgrade from using Datastore, to using Firestore in Datastore mode, which was a large amount of code change:  https://cloud.google.com/datastore/docs/firestore-or-datastore

I believe the bundled app engine web server "appengine:run" is now deprecated.  You now need to provide your own web server.  All Google gives you is an installed Java version, and Java libraries to interface with their systems.  How you run them, is now up to you.  Check out the "Framework flexibility" section:  https://cloud.google.com/appengine/migration-center/standard/migrate-to-second-gen/java-differences#framework_flexibility

Disclaimer:  Google has legacy bundled services you can use, and that might include a web server somehow.  I haven't looked too much into it, as I wanted my project to be on the latest, and get off all the legacy stuff.  Plus, once you get off the legacy stuff, you are no longer on Googles proprietary web server and datastore, so moving your app somewhere else becomes a lot easier if you ever needed to.

Shameless self promotion:  I just finished a project for Nasdaq, so I'll be looking for work in the next few weeks, if you needed someone with experience, happy to chat:  https://www.linkedin.com/in/craigmit75/ 

Cheers.

[Thomas Broyer]

You need to pass the -agentlib:… as <jvmArgs> of the appengine plugin, as it will fork a new JVM

https://cloud.google.com/appengine/docs/legacy/standard/java/maven-reference#appenginerun

[Daniel Webb]

Thanks for the suggestion Tim, I was really hopeful but I think I'm running in the Debug perspective but the breakpoints are still not triggering :-(

[Daniel Webb]

Hi Craig,

Ahh right, so although it's working at the moment with  appengine:run this is being phased out so I'd better be moving to a standalone server.

[Daniel Webb]

Hi Thomas,

Aha!! You are correct, thank you - I have added it to my POM and now the breakpoints are getting triggered :-)

Is there a way of limiting this configuration to a specific run configuration, or sometning? The way I have it set up I think the flags are passed every time?

<plugin>

<groupId>com.google.cloud.tools</groupId>

<artifactId>appengine-maven-plugin</artifactId>

<version>2.7.0</version>

<configuration>

<jvmFlags>

<jvmFlag>-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000</jvmFlag>

</jvmFlags>

</configuration>

</plugin>

[tim_mac...@yahoo.co.uk]

This might be useful  github.com/timmacp/AppEngineGwt/tree/main

Its based on github.com/tbroyer/gwt-maven-archetypes 

& Google Cloud Platform samples for App Engine with Java 11+

github.com/GoogleCloudPlatform/java-docs-samples/tree/main/appengine-java11/appengine-simple-jetty-main which shows how to have a separate jar module which run the WAR using the  java command.

As in the GWT archetype it uses Jetty Maven Plugin for the development server & it covers Eclipse debugging,

appengine-maven-plugin is only for appengine:deploy