Vaadin-maven-plugin "java.lang.ClassNotFoundException"

General
1

Hi, I am having an exception in the “vaadin-maven-plugin”. I made a configuration in order to use a custom Jackson object mapper that works fine when I run the project from IDE, but it is causing a “java.lang.ClassNotFoundException” when I try to generate the production package.

This is the plugin configuration with the jackson mapper:

 			<plugin>
                <groupId>com.vaadin</groupId>
                <artifactId>vaadin-maven-plugin</artifactId>
                <version>${vaadin.version}</version>
                <configuration>
				    <parser>
				        <plugins>
							<disableAllDefaults>true</disableAllDefaults>
				        	<use>
				                <plugin>
				                    <name>com.vaadin.hilla.parser.plugins.backbone.BackbonePlugin</name>
				                    <configuration implementation="com.vaadin.hilla.parser.plugins.backbone.BackbonePluginConfiguration">
				                    	<objectMapperFactoryClassName>com.example.MyObjectMapperFactory</objectMapperFactoryClassName>
				                    </configuration>
				                </plugin>
				                <plugin>
				                    <name>com.vaadin.hilla.parser.plugins.transfertypes.TransferTypesPlugin</name>
								</plugin>
				                <plugin>
				                    <name>com.vaadin.hilla.parser.plugins.nonnull.NonnullPlugin</name>
								</plugin>
				                <plugin>
				                    <name>com.vaadin.hilla.parser.plugins.subtypes.SubTypesPlugin</name>
								</plugin>
				                <plugin>
				                    <name>com.vaadin.hilla.parser.plugins.model.ModelPlugin</name>
								</plugin>					
							</use>
				        </plugins>
				    </parser>
			    </configuration>
            </plugin

$ ./mvnw -X -Pproduction clean compile com.vaadin:vaadin-maven-plugin:24.4.6:build-frontend

Caused by: java.lang.ClassNotFoundException: com.example.MyObjectMapperFactory
    at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass (SelfFirstStrategy.java:50)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass (ClassRealm.java:271)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:247)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:239)

I cannot figure out how to solve the ClassNotFoundException, any idea is really appreciated.

Thanks,
Ed

2

Is com.example.MyObjectMapperFactory a class in your project? If so, most likely it is not seen by the plugin classloader

3

Yes, its a class in the project compiled in ./target/classes directory. I think the same, the pluggin is not seeing those clases. What are my options? Is there any parameter I can add in pom.xml or in the command line to pass the path to the comiled class or something similar so the pluggin can load it?

4

Only thing that comes in mind at the moment, is to put the class in a separate module and add the artifact to the plugin definition dependencies

5

Thank you for your comments. Do you mean creating a new maven dependency/artifac with the MyObjectMapperFactory inside? I wonder now if there is a maven pluggin that allows me to run the vaadin-maven-plugin with an altered classpath. :/

6

Yes, I mean create a new independent maven module/project with the customized class.

I’m not aware of any workaround to augment the plugin class loader by configuring the POM file, other than adding entries in the <dependencies> section of the plugin configuration.

1 Like
7

Marco is right that’s the correct way

1 Like
8

Yes, that will work. However, because chances of modiffing the mapper are high I ended up modifing the mojo build pluggin so I added a “includeInRealmPaths” property so I can add extra paths to the ClassRealm. Here is the code in case helps anybody.

    @Parameter(property = "includeInRealmPaths")
    private List<String> includeInRealmPaths;
    
    @Override
    public void execute() throws MojoExecutionException, MojoFailureException {
        getLog().debug("Starting execution of mojo BuildFrontendMojo");
            final PluginDescriptor pluginDescriptor = (PluginDescriptor) getPluginContext().get("pluginDescriptor");
            if (includeInRealmPaths != null && !includeInRealmPaths.isEmpty()) {
                getLog().debug("Inclusions in realm detected");
                for (String path : includeInRealmPaths) {
                    getLog().debug("Including '" + path + "'");
                    final ClassRealm classRealm = pluginDescriptor.getClassRealm();
                    try {
                        classRealm.addURL(new File(path).toURI().toURL());
                    } catch (MalformedURLException e) {
                        getLog().error("I could not include in realm" + e);
                        e.printStackTrace();
                    }
                }
            } else {
                getLog().debug("No inclusions in realm requested");
            }
        super.execute();
    }
}

And I use that new config as follows

<configuration>
   <includeInRealmPaths>
      <includeInRealmPath>./target/classes/</includeInRealmPath>
   </includeInRealmPaths>
...
</configuration>

It’s working fine so far, and also I am satified avoid creating an new artifact just for a single class.

Thanks for your comments and support mates.

9

Good work!
Do you mind creating a feature request issue on the Hilla repository explaining the problem and posting your solution?
Hilla team may be interested in improving the official plugin.