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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

Retrieve dependencies source code in maven project

In my maven project I have plenty of dependencies which source code I need to get.
I know there is maven-dependency plugin with unpack-dependencies goal in it
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.10</version>
<executions>
<execution>
<id>resolve-dependecies</id>
<phase>process-sources</phase>
<goals>
<goal>sources</goal>
</goals>
<configuration>
<classifier>sources</classifier>
<includeParents>true</includeParents>
<type>java-source</type>
</configuration>
</execution>
<execution>
<id>src-dependencies</id>
<phase>process-sources</phase>
<goals>
<goal>unpack-dependencies</goal>
</goals>
<configuration>
<classifier>sources</classifier>
<failOnMissingClassifierArtifact>false</failOnMissingClassifierArtifact>
<outputDirectory>${project.basedir}/Utils/src</outputDirectory>
<type>java-source</type>
</configuration>
</execution>
</executions>
</plugin>
But when I use it a lot files "have NOT been resolved".
e.g.
...
org.jboss:jboss-parent:java-source:sources:5
org.apache.cxf:cxf-parent:java-source:sources:3.0.3
org.apache:apache:java-source:sources:13
org.apache:apache:java-source:sources:9
org.liquibase:liquibase-parent:java-source:sources:3.5.0
org.apache.commons:commons-parent:java-source:sources:5
org.eclipse.jetty.orbit:jetty-orbit:java-source:sources:1
...
In pom.xml I didn't specify any repository for dependencies, so by default maven central repository is using.
I also tried to decompile (Fernflower, Procyon, JAD projects) my project jar file which contains all dependencies. But after decompiling hundreds of errors appeared in result java files.
I still hope to solve this issue using maven tools.
Thanks in advance for any help.
EDIT
Unresolved artifacts directly not specified in pom.xml

I see a couple of dependencies with *-parent. Given the name I guess these are merely parent poms which probably don't contain any java sources. For the remaining ones, are you sure that there are artifacts with the java sources?
UPDATE: I checked the list you shown within your question whether there are sources and there weren't. What I noted is that all of them have packaging POM. You might skip these by including <includeClassifiers>sources</includeClassifier> within your configuration

maven assembly plugin: add a file into a dependency jar

There is this maven module, say prj-package-module, to package the project artifacts into a tar file using maven-assembly-plugin. There are also jars added as dependencies in the prj-package-module/pom.xml and packaged into the tar file.
Now the requirement is to add a file, prj-pakacge-module/src/main/resources/file.xml to one of these dependency jars before packaging into the tar file. How can I achieve this?
Edit: The file is a JNLP with list of dependency jars dynamically added to it. For security reasons, Javaws also requires the JNLP file to be added a jar and the jar to be signed. This is where I hit the problem.

Here is a maven solution to dynamically unpack an existing dependency, add (copy) a resource to the unpacked folder, repack (jar) the hole and as such get a modified copy of the initial jar.
A sample pom file doing exactly that for the junit dependency:
<build>
<plugins>
<!-- unpack step -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.10</version>
<executions>
<execution>
<id>unpack</id>
<phase>prepare-package</phase>
<goals>
<goal>unpack</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<type>jar</type>
<outputDirectory>${project.build.directory}/unpack-tmp</outputDirectory>
<includes>**/*.class,**/*.xml</includes>
</artifactItem>
</artifactItems>
</configuration>
</execution>
</executions>
</plugin>
<!-- add the additional resource step -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>2.7</version>
<executions>
<execution>
<id>copy-resources</id>
<phase>prepare-package</phase>
<goals>
<goal>copy-resources</goal>
</goals>
<configuration>
<outputDirectory>${basedir}/target/unpack-tmp</outputDirectory>
<resources>
<resource>
<directory>src/main/resources</directory>
<include>test.properties</include>
</resource>
</resources>
</configuration>
</execution>
</executions>
</plugin>
<!-- repack step -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.6</version>
<executions>
<execution>
<id>repack</id>
<phase>prepare-package</phase>
<goals>
<goal>jar</goal>
</goals>
<configuration>
<classesDirectory>${basedir}/target/unpack-tmp</classesDirectory>
<finalName>junit-modified</finalName>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
What it is actually doing:
As part of the prepare-package phase we are adding three steps to create a modified jar from a dependency
First step: unpack the dependency via the Maven Dependency Plugin and its unpack goal: an unpacked folder will be created to the tmp folder unpack-tmp
Second step: copy the concerned resource via the Maven Resources Plugin and its copy-resources goal.
Third step: re-pack the whole via the Maven Jar Plugin and its classic jar goal
Running the sample above, the junit-modified.jar file will appear in the target folder of the maven project.
The order of the plugin configurations above is important to respect the steps flow as part of the same phase.
Then, you have one additional file to add to your fat-jar, which is indeed the modified jar you were probably looking for.
If you don't need a dynamic approach, a better approach would be to do it once and have a classified version of that dependency as explained in this other SO post.
Alternatively, move it to a Maven profile so that at least it is not part of the default build.

It seems that you're trying to modify a dependency of the maven project before packaging it into the final artifact of the project.
This is dodgy. If that jar/library (the dependency) is yours, then modify the pom of that jar, rebuild it, and then have the current project resolve the latest artifact.
If, otherwise, the dependency jar is not yours, then it should suffice to have the resource (prj-pakacge-module/src/main/resources/file.xml) in the current project (the one you're building now), as the end result will be the same (as long as the assembly plugin is set to flatten all artifact jars in the target uber/fat jar...

Prevent maven module from being built with no activated profile

I have a multi-module maven project with parent POM. One child of project is customized for different environments by profiles and parent pom also build needed modules depending on selected environment (profile).
I want to prevent building (read as "to run mvn package" in child module) customized child project without profile activated, because there is no "generic" or "default" version for environment. Another words, I want to force developer to use environment-dependent profile.
Is it possible to do so?

Maven Enforcer is made just for this requirement. Simply add the required profiles.
<project>
[...]
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.4</version>
<executions>
<execution>
<id>enforce-all-profiles-are-activated</id>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<requireActiveProfile>
<profiles>first,second</profiles>
</requireActiveProfile>
</rules>
<fail>true</fail>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
[...]
</project>

maven checkstyle unable to find where to insert the includes configuration

We have a maven project where I use a checkstyle plugin in the build process and we are very fond of checkstyle. Anyway recently we need to insert web services to our project. The web services classes are not compatible with checkstyle so we want to exclude them when building. So as a way of exclude we want to specify the folders to be included.
I have come across maven.checkstyle.includes and sourceDirectory of checkstyle plugin. But I could not be able to figure out how to use them in pom.xml.
Anyone have an idea?
Here is my checkstyle section of pom.xml
<build>
...
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-checkstyle-plugin</artifactId>
<version>2.8</version>
<executions>
<execution>
<phase>process-sources</phase>
<goals>
<goal>check</goal>
</goals>
</execution>
</executions>
<configuration>
<failsOnError>true</failsOnError>
<consoleOutput>true</consoleOutput>
<configLocation>sample_config.xml</configLocation>
<sourceDirectory>${maven.checkstyle.includes}</sourceDirectory>
</configuration>
</plugin>
...
</build>

<excludes>my/package/**/*</excludes>
Add this to your configuration section. These are ant style patterns and you can give the plugin multiple patterns by separating them with a comma.