add support for spring-boot:run into flow-maven-plugin

[vlukashov]

As a developer I want to use the Spring Boot maven plugin to run my Flow app in the production mode (because running the spring-boot:run maven goal is easier then deploying a .war file to a servlet container, and because it's easier to debug the app started that way). Currently (with the version 1.0.0.alpha19 of the flow-maven-plugin) that requires extra configuration and manual action when re-building the app.

The flow-maven-plugin runs a Gulp build script and outputs production-ready frontend files into the folder defined in the transpileOutputDirectory configuration property (${project.build.directory}/${project.build.finalName}/ by default).

When the app is packaged in a .war file, this would be the context root. That matches the default context paths for the frontend resources expected by Flow (see FRONTEND_URL_ES5_DEFAULT_VALUE). However, when the app is started with spring-boot:run, the context root is src/main/webapp, and Flow would search for frontend resources there.

When the app started with jetty:run, this can be worked around by instructing the Maven Jetty plugin to add extra resource folders to the context:

<plugin>
    <groupId>org.eclipse.jetty</groupId>
    <artifactId>jetty-maven-plugin</artifactId>
    <configuration>
        <webAppConfig>
            <resourceBases>
                <resourceBase>${project.build.directory}/${project.build.finalName}</resourceBase>
            </resourceBases>
        </webAppConfig>
    </configuration>
</plugin>

But there is no similar parameters for the Spring-Boot Maven plugin.

A semi-OK workaround for this issue is to configure the Flow Maven plugin to output the transpiled frontend code into a subfolder in src/main/webapp (<transpileOutputDirectory>${frontend.directory}/build</transpileOutputDirectory>), and then also override the default Flow settings for the frontend resource folders with -Dvaadin.frontend.url.es5=context://frontend/build/frontend-es5/ and -Dvaadin.frontend.url.es6=context://frontend/build/frontend-es6/.

The problem with this workaround (apart from the fact that it adds generated code into the source folder) is that when running the flow-maven-plugin in the second time, the Gulp build script fails to clean the output folder (because it is outside of the Gulp's working directory):

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 44.049 s
[INFO] Finished at: 2018-02-08T11:32:33+02:00
[INFO] Final Memory: 48M/1469M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal com.vaadin:flow-maven-plugin:1.0.0.alpha19:package-for-production (default) on project bakery-app-starter-flow-spring: Execution default of goal com.vaadin:flow-maven-plugin:1.0.0.alpha19:package-for-production failed: Transpilation with gulp has failed: 'gulp build_es6' failed. org.apache.commons.exec.ExecuteException: Process exited with an error: 1 (Exit value: 1) -> [Help 1]

That is, this workaround requires deleting the build output folder manually. Please improve the developer experience for this use case.

[tsuoanttila]

Would <folders> work for this?

[vlukashov]

@tsuoanttila does not looks like that. The documentation says it adds more folders to the classpath, but apparently not to the servlet context. I've tried adding the ${project.build.directory}/${project.build.finalName} folder and that did not add the resources from that folder to the context.

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <folders>
            <folder>${project.build.directory}/${project.build.finalName}</folder>
        </folders>
    </configuration>
</plugin>

[vlukashov]

I ended up using the default config for the flow maven plugin (outputs the transpiled frontend sources to ${project.build.directory}/${project.build.finalName}/frontend-es5 and ${project.build.directory}/${project.build.finalName}/frontend-es6), and copy the frontend-esX folders into src/main/webapp/ with the maven resources plugin.

With that approach both the .war context and the mvn spring-boot:run context have the frontend files where Flow expects to find them (/frontend-es5 and /frontend-es6). Restarting the app with mvn spring-boot:run also works. But that's a manual configuration that ideally should not be there.

[SomeoneToIgnore]

Now the plugin is able to remove the external directories: #3540

[denis-anisimov]

Issue moved to vaadin/spring #267 via ZenHub