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Handle different source folder in Eclipse

The Project I am working on has the regular src/main and src/test folders, but they recently introduced src/integration-test, which is supposed to contain, as the name suggests, integration-tests.
Unfortunately I can't seem to make this work with Maven and Eclipse. I tried adding a source folder, but Eclipse is not able to resolve the dependencies needed for the integration-tests and fails to compile the test-classes. I also can't start the tests with JUnit.
The source folder was added to the build path, but it did not help.
All other developers in my team use IntelliJ and report that they don't have these issues at all. But it´s bound to work with Eclipse as well, right?

You should handle this with maven by adding the source folder to the build:
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>3.0.0</version>
<executions>
<execution>
<id>add-test-source</id>
<phase>generate-test-sources</phase>
<goals>
<goal>add-test-source</goal>
</goals>
<configuration>
<sources>
<source>src/integration</source>
</sources>
</configuration>
</execution>
</executions>
</plugin>
In this example the build will add a src/integration folder where you can put other test classes.
For more information check the build helper plugin documentation.

Groovy Maven plugin, marking target stub as source directory

I am using gmavenplus-plugin, below is the configuration details
<plugin>
<groupId>org.codehaus.gmavenplus</groupId>
<artifactId>gmavenplus-plugin</artifactId>
<version>1.6</version>
<executions>
<execution>
<goals>
<goal>addSources</goal>
<goal>addTestSources</goal>
<goal>generateStubs</goal>
<goal>compile</goal>
<goal>generateTestStubs</goal>
<goal>compileTests</goal>
<goal>removeStubs</goal>
<goal>removeTestStubs</goal>
</goals>
</execution>
</executions>
</plugin>
After each time maven clean build, intellij's settings gets updated and it maker generated stub as source and test source folders. Ideally goal removeStubs and removeTestStubs should remove it from source. All examples on internet is based on above configuration only.
Am I missing something.

The way IntelliJ hooks into the GMavenPlus (and GMaven) lifecycle was by expecting specific goal names. 1.6 fixes this by renaming the goals to match IntelliJ's expectations.

Automatically generate Java from .proto with maven/m2e in Eclipse IDE

For my team, I'd like to configure maven/eclipse build to automatically generate Java code from *.proto files (in a project that uses gRPC). Currently one needs to run mvn generate-source or mvn protobuf:compile (as in plugin usage page). Or what is the same add Run configuration to invoke maven goal compile.
Whenever Eclipse Maven project is refreshed (Alt+F5) or IDE is restarted, project is rebuilt but without what should appear in target/generated, thus turning project into red. So one need to generate and refresh project (F5). UPDATE Eclipse has needed source folders configured in .clathpath file.
As I know that should be m2e connector, but I could only find one https://github.com/masterzen/m2e-protoc-connector for the oldest Googles plugin com.google.protobuf.tools:maven-protoc-plugin, that is even not mentioned currently at https://github.com/grpc/grpc-java
We use exactly referenced/recommended
<groupId>org.xolstice.maven.plugins</groupId>
<artifactId>protobuf-maven-plugin</artifactId>
that is:
<build>
<extensions>
<extension>
<groupId>kr.motd.maven</groupId>
<artifactId>os-maven-plugin</artifactId>
<version>1.4.1.Final</version>
</extension>
</extensions>
<plugins>
<plugin>
<groupId>org.xolstice.maven.plugins</groupId>
<artifactId>protobuf-maven-plugin</artifactId>
<version>0.5.0</version>
<configuration>
<protocArtifact>com.google.protobuf:protoc:3.1.0:exe:${os.detected.classifier}</protocArtifact>
<pluginId>grpc-java</pluginId>
<pluginArtifact>io.grpc:protoc-gen-grpc-java:1.0.1:exe:${os.detected.classifier}</pluginArtifact>
</configuration>
<executions>
<execution>
<goals>
<goal>compile</goal>
<goal>compile-custom</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
Related:
Linking to generated Java protobuf code in Eclipse
looked at this but that author was using other older, not supported now plugin : Eclipse build loop caused by protobuf generated code (related to Maven Project Builder)
P.P.S That plugin https://github.com/igor-petruk/protobuf-maven-plugin however has continuation as https://github.com/os72/protoc-jar-maven-plugin

Instead of using org.xolstice.maven.plugins:protobuf-maven-plugin my team has used com.github.os72:protoc-jar-maven-plugin to generate the message classes. I believe they are the same since under the hood they all seem to be using the tools from Google.
I am not using any m2e connectors for this plugin (Edit: protoc-jar-maven-plugin's m2e connector is bundled with it so no extra installation is needed, which is why it seemed like I wasn't using one, but technically I was, but this doesn't really matter). Unfortunately the changes in the .proto file are not "automatically" propagated to the generated .java files, you need to manually run Maven or trigger the project to be built in Eclipse (instructions below), but fortunately the target/generated-sources file is not vanishing or emptying or anything strange like what you describe.
If you want to rebuild the .java files from the .proto classes without using mvn clean compile from the command line you can clean the Eclipse project . Project → Clean... → select your project → Select build option (only shows if you have "Build Automatically" from the Project menu is unchecked).
I was able to do this in the latest Eclipse Neon (it will probably work in later ones too, but I don't know for certain).
Below is the POM I am using. I don't think it requires any special explanation, my solution is to simply use a different plugin than the one you are using. (If some explanation is needed I'll be happy to provide it though.)
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>io.github.jacksonbailey</groupId>
<artifactId>protobuf-m2e-sample</artifactId>
<version>0.1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>com.google.protobuf</groupId>
<artifactId>protobuf-java</artifactId>
<version>3.1.0</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>com.github.os72</groupId>
<artifactId>protoc-jar-maven-plugin</artifactId>
<version>3.1.0.1</version>
<executions>
<execution>
<phase>generate-sources</phase>
<goals>
<goal>run</goal>
</goals>
<configuration>
<protocVersion>3.1.0</protocVersion>
<inputDirectories>
<include>src/main/resources</include>
</inputDirectories>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

for protobuf-maven-plugin
Thanks to sergei-ivanov answer in https://github.com/xolstice/protobuf-maven-plugin/issues/16, that gave link https://github.com/trustin/os-maven-plugin#issues-with-eclipse-m2e-or-other-ides :
One need to download os-maven-plugin-x.x.x.Final.jar (the version as in your pomx.ml) and put it into the <ECLIPSE_HOME>/plugins directory.
After that Eclipse will generate source on project clean, including after Maven -update project... (Alt+F5), but not after Project -> Build (or with default Build Automatically). Also on IDE start it will not compile.
Yes, that is illogical:
Project - Clean will generate and compile Java source
but
Project - Build will not.
P.S. Raised Bug 507412

Both eclipse and vscode can automatically compile proto when changed.
<plugin>
<groupId>kr.motd.maven</groupId>
<artifactId>os-maven-plugin</artifactId>
<version>1.6.2</version>
<executions>
<execution>
<phase>initialize</phase>
<goals>
<goal>detect</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.xolstice.maven.plugins</groupId>
<artifactId>protobuf-maven-plugin</artifactId>
<version>0.6.1</version>
<configuration>
<protocArtifact>com.google.protobuf:protoc:3.12.0:exe:${os.detected.classifier}</protocArtifact>
<pluginId>grpc-java</pluginId>
<pluginArtifact>io.grpc:protoc-gen-grpc-java:1.32.1:exe:${os.detected.classifier}</pluginArtifact>
</configuration>
<executions>
<execution>
<goals>
<goal>compile</goal>
<goal>compile-custom</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<source>8</source>
<target>8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
See: https://github.com/trustin/os-maven-plugin#issues-with-eclipse-m2e-or-other-ides

Maven Javadoc aggregate-jar plugin fails because of unresolved dependencies

I have multi-module Maven project in which I run the maven-javadoc-plugin to generate javadoc. In my parent pom.xml I have defined the plugin build as follows:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.9.1</version>
<configuration>
<!-- Default configuration for all reports -->
</configuration>
<executions>
<execution>
<id>aggregate</id>
<goals>
<goal>aggregate-jar</goal>
</goals>
<phase>install</phase>
<configuration>
<!-- Specific configuration for the aggregate report -->
</configuration>
</execution>
</executions>
</plugin>
When I run mvn clean install the build fails with unresolved dependencies, but I see the following warning:
[WARNING] The dependency:
[my.application:my-module:jar:1.7.1] can't be resolved but
has been found in the reactor (probably snapshots). This dependency
has been excluded from the Javadoc classpath. You should rerun javadoc
after executing mvn install.
As I am currently building my-module 1.7.1, I would assume Maven to detect this and run the aggregate-jar after building my-module, but for some reason it expects my-module to already be installed in a repo.
My Maven version is 3.0.4. Please keep in mind that I am new to Maven builds so this may be a very simple question, but I was not able to find any answer.
Some observations:
The build succeeds if I first run mvn clean install without the javadoc plugin aggregate-jar goal
The javadoc plugin aggregate goal runs fine.
This bug refers exactly to my issue, but should have been solved in Maven 3 (2010)

I run this command in my parent pom and this is how I do it without issues:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.10.1</version>
<executions>
<execution>
<id>attach-javadocs</id>
<goals>
<goal>aggregate</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
When I want to generate the docs, I do mvn javadoc:aggregate

Maven checkstyle https configuration

I have the following maven check style plugin configuration
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-checkstyle-plugin</artifactId>
<configuration>
<consoleOutput>true</consoleOutput>
<configLocation>https://someUtl.com/file.xml</configLocation>
</configuration>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>check</goal>
</goals>
</execution>
</executions>
</plugin>
Pay attention on
<configLocation>https://someUtl.com/file.xml</configLocation>
file.xml can be downloaded by browser, but it require a login and password. Is there a way to specify these login/password in maven or in plugin configuration?

Underneath, this uses Plexus which in turn pretty much does URL.openStream().
This answer shows how an Authenticator can be used for that in Java code, but I was unable to find a Maven equivalent for that. I'm inclined to say that it's not possible.
Alternatively, you might be able to download the file in a separate mojo execution, then point the configLocation to the downloaded file, which could be anywhere down your target folder.
I think that this answer gives a few nice ideas about how to download files in Maven. Their first is that if your file is a Maven artifact, you could use the Maven Dependency Plugin.
And then we come full circle, because if your Checkstyle configuration were to be contained in a Maven artifact, you would not have to set configLocation to a remote location, but you'd add that artifact as a dependency of your Checkstyle plugin execution. Since Maven defines everything in terms of dependencies, that is my way to go, and that is exactly how I set up my own Checkstyle configurations.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-checkstyle-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>check</goal>
</goals>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>com.totaalsoftware.incidentmanager</groupId>
<artifactId>checkstyle-config</artifactId>
<version>2.0.0-SNAPSHOT</version>
</dependency>
</dependencies>
<configuration>
<configLocation>checkstyle.config.xml</configLocation>
...
</configuration>
</plugin>
Clearly, in the above example, checkstyle.config.xml resides in the root of the checkstyle-config JAR.