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How to get PMD maven plugin to skip generated source code?

So I'm creating a maven plugin using the maven-plugin-plugin. The HelpMojo in maven-plugin-plugin generates a java source file.
Unfortunately, PMD is picking this up and complaining about it. Is there a way to have PMD ignore just a single source file? Thanks!
Maven PMD Configuration:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-pmd-plugin</artifactId>
<executions>
<execution>
<id>pmd-verify</id>
<goals>
<goal>check</goal>
<goal>cpd-check</goal>
</goals>
<configuration>
<printFailingErrors>true</printFailingErrors>
</configuration>
</execution>
</executions>
</plugin>

Generated sources usually end up (with maven) in a subdirectory in target/generated-sources, for the maven-plugin-plugin it's target/generated-sources/plugin.
You can exclude these complete directories with excludeRoots, e.g.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-pmd-plugin</artifactId>
<executions>
<execution>
<id>pmd-verify</id>
<goals>
<goal>check</goal>
<goal>cpd-check</goal>
</goals>
<configuration>
<printFailingErrors>true</printFailingErrors>
<excludeRoots>
<excludeRoot>target/generated-sources/plugin</excludeRoot>
</excludeRoots>
</configuration>
</execution>
</executions>
</plugin>
There is also a file based exclude option.

Maven MOJO: is it possible to customize the auto-generated plugin.xml

I'm writing a Maven MOJO and I wish to modify the auto generated plugin.xml.
For example, I would like to have a different version written there and have a different set of dependencies.
Is is possible to customize this file? I've tried using the maven-plugin-plugin:3.5:descriptor goal in my pom like this:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-plugin-plugin</artifactId>
<version>3.5</version>
<configuration>
<mojoDependencies>com.company:something</mojoDependencies>
<skipErrorNoDescriptorsFound>true</skipErrorNoDescriptorsFound>
</configuration>
<executions>
<execution>
<id>default-descriptor</id>
<goals>
<goal>descriptor</goal>
</goals>
<phase>process-classes</phase>
</execution>
</executions>
</plugin>
It seems to have zero effect.
Can anyone provide an example to how it can be done?

HOw to use jsonschema2pojo in maven's POM

I have a JSON File and I want to convert it to POJO, for this I am using the plugin of org.jsonschema2pojo in maven. I am not able to generate the resultant pojo.Here's the snippet from pom.xml
<build>
<plugins>
<plugin>
<groupId>org.jsonschema2pojo</groupId>
<artifactId>jsonschema2pojo-maven-plugin</artifactId>
<version>0.4.23</version>
<configuration>
<sourceDirectory>${basedir}/src/main/resources/schema</sourceDirectory>
<targetPackage>${basedir}/src/main/resources/result</targetPackage>
</configuration>
<executions>
<execution>
<goals>
<goal>generate</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
I am using the generate sources goal in maven. My expectation is that it should give me pojo files at ${basedir}/src/main/resources/result location. However I am getting so. Please help me out.
Thanks,
Rajit

You want to use <outputDirectory> instead of <targetPackage>. More details here:
http://joelittlejohn.github.io/jsonschema2pojo/site/0.4.23/generate-mojo.html#outputDirectory
http://joelittlejohn.github.io/jsonschema2pojo/site/0.4.23/generate-mojo.html#targetPackage
Target package is the Java package you want your types to use, e.g. com.youcompany.model.
Also, typically you want the generated output to go into the target directory, not src. Derived files usually go there since anything inside target is usually omitted from source control. You don't need to specify outputDirectory if you don't want to, by default the generated output will go into /target/java-gen.

Below code works for me.
<plugin>
<groupId>org.jsonschema2pojo</groupId>
<artifactId>jsonschema2pojo-maven-plugin</artifactId>
<executions>
<execution>
<id>1</id>
<configuration>
<annotationStyle>jackson2</annotationStyle>
<includeAdditionalProperties>false</includeAdditionalProperties>
<sourcePaths>
<sourcePath>${project.basedir}/src/main/resource/jsd/your_schema.json</sourcePath>
</sourcePaths>
<targetPackage>your target package</targetPackage>
</configuration>
<goals>
<goal>generate</goal>
</goals>
</execution>
<execution>
<id>2</id>
<configuration>
<annotationStyle>jackson2</annotationStyle>
<includeAdditionalProperties>false</includeAdditionalProperties>
<sourcePaths>
<sourcePath>${project.basedir}/src/main/resource/jsd/your_schema2.json</sourcePath>
</sourcePaths>
<targetPackage>your target package</targetPackage>
</configuration>
<goals>
<goal>generate</goal>
</goals>
</execution>
</executions>
</plugin>

Use both targetPackage and outputDirectory.
<plugin>
<groupId>org.jsonschema2pojo</groupId>
<artifactId>jsonschema2pojo-maven-plugin</artifactId>
<version>1.0.2</version>
<configuration>
<sourceDirectory>${basedir}/src/main/resources/schema</sourceDirectory>
<outputDirectory>src/main/java</outputDirectory>
<targetPackage>com.your.package</targetPackage>
</configuration>
<executions>
<execution>
<goals>
<goal>generate</goal>
</goals>
</execution>
</executions>
</plugin>

Maven and JavaDoc: install additional (generated) files

My project can generate some additional help files automatically from the source code.
How do I have maven install these files into the generated JavaDoc package?
I couldn't fingure out how to have Maven:
run some class to generate the additional documentation, e.g. compile and launch src/main/java/mypackage/ListOptions.java aka mypackage.ListOptions to produce a list of all available options/modules/examples/etc. .
install the output files (I only could get Maven to install files from src/main/javadoc/resources into the site/apidocs/resources subfolder; but I want this documentation to live in the top level site/apidocs folder; more precisely I don't care about the site part at all, but about having a complete documetation in mypackage-0.1.0-SNAPSHOT-javadoc.jar; including non-Javadoc-generated auxillary information linked from javadoc).
Minimal example - Plugin configuration for maven:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.9.1</version>
<executions>
<execution>
<id>attach-javadocs</id>
<goals>
<goal>jar</goal>
</goals>
</execution>
</executions>
<configuration>
<docfilessubdirs>true</docfilessubdirs>
</configuration>
</plugin>
Directory layout:
./pom.xml
./src/main/java/foobar/GenerateNonstatic.java
./src/main/javadoc/staticfile.js
./src/main/javadoc/resources/insubfolder.png
mvn package produces: javadoc in ./target/apidocs and ./target/foobar-0.0.1-SNAPSHOT-javadoc.jar. The file target/apidocs/resources/insubfolder.png ends up in folder target/apidocs/resources (and the .jar), but the staticfile.js is not installed.
How to run GenerateNonstatic.java to have the output included in the javadoc .jar is unclear to me. I don't see a hook to have exec:exec it run after javadoc, and before ./target/foobar-0.0.1-SNAPSHOT-javadoc.jar is built...

Long story, short answer. Both the javadoc:javadoc and javadoc:jar mojos have their drawbacks. The first is meant to build the javadoc for reporting; the latter will build the javadoc (into a different directory) and produce a jar package.
Some of the suggested answers did not work well because of this - they would execute javadoc twice.
But I noticed that javadoc does not care if the folder already exists or contains files.
So my solution is simple: generate the desired additional files in prepare-package, and the regular javadoc:jar task adds the regular javadoc and pacakges it nicely.
This will work as long as you don't intend to modify files generated by javadoc (which I, fortunately, don't - I only add additional documentation.
The resulting pom.xml is like this:
<plugins>
<!-- copy additional javadoc resources -->
<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>${project.build.directory}/apidocs</outputDirectory>
<resources>
<resource>
<directory>${basedir}/src/main/javadoc</directory>
<excludes>
<!-- overview.html is integrated by javadoc -->
<exclude>${basedir}/src/main/javadoc/overview.html</exclude>
</excludes>
</resource>
</resources>
</configuration>
</execution>
</executions>
</plugin>
<!-- Generate additional files for javadoc -->
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.3.2</version>
<executions>
<execution>
<id>generate-extra-javadoc</id>
<phase>prepare-package</phase>
<goals>
<!-- java is okay, but you only can have one -->
<goal>exec</goal>
</goals>
<configuration>...</configuration>
</execution>
</executions>
</plugin>
<!-- Build JavaDoc -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.10.1</version>
<executions>
<execution>
<id>attach-javadocs</id>
<phase>package</phase>
<goals>
<goal>jar</goal>
</goals>
</execution>
</executions>
</plugin>

Eric,
If you are uncomfortable modifying the javadoc executable, another option is to break apart your javadoc call into 2 separate steps (javadoc and jar) and make your call between them by manipulating the Maven build lifecycle via <phase> tag:
phase: generate-sources => maven-javadoc-plugin:javadoc
phase: compile => exec-maven-plugin:java
phase: package => maven-javadoc-plugin:jar
note: use exec:java, not exec:exec to run java classes
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.9.1</version>
<executions>
<execution>
<id>generate-javadocs</id>
<phase>generate-sources</phase>
<goals>
<goal>javadoc</goal>
</goals>
</execution>
<execution>
<id>attach-javadocs</id>
<phase>package</phase>
<goals>
<goal>jar</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.3.2</version>
<executions>
<execution>
<id>generate-nonstatic-javadocs</id>
<phase>compile</phase>
<goals>
<goal>java</goal>
</goals>
<configuration>
<mainClass>foobar.GenerateNonstatic</mainClass>
</configuration>
</execution>
</executions>
</plugin>

To answer your first question: Run a commandline command with the Exec-Maven-Plugin or use the Maven-Ant-Plugin and embed custom tasks.

Eric,
Your example is indeed helpful. Please do try to always include concrete examples as much as possible when asking the question.
The simplest approach would be to write your own Alternate Javadoc tool and pass that into Maven via the <javadocExecutable> tag. This example comes from the link above:
<project>
...
<reporting> (or <build>)
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.10.1</version>
<configuration>
<javadocExecutable>C:\jdk1.6.0\bin\javadoc.exe</javadocExecutable>
...
</configuration>
</plugin>
...
</plugins>
</reporting> (or </build>)
...
</project>
Hope that helps.

How to use of the Maven Enforcer plugin?

I'd like to use the Maven Enforcer plugin to check to see if I have duplicate classes on my path.
I've tried the example from here.
But when I run it like this:
mvn enforcer:enforce
I get this error:
Failed to execute goal
org.apache.maven.plugins:maven-enforcer-plugin:1.0.1:enforce
(default-cli) on project datapopulator: The parameters 'rules' for
goal org.apache.maven.plugins:maven-enforcer-plugin:1.0.1:enforce are
missing or invalid
Is there a way to use this correctly?
EDIT #1
If changing my config to this:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.0.1</version>
<executions>
<execution>
<id>enforce-versions</id>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<AlwaysPass />
</rules>
<fail>true</fail>
</configuration>
</execution>
</executions>
</plugin>
Produces the same error.

The reason why your first version did not work is because there is a difference between a plug-in configuration inside the execution tag and a plug-in configuration outside the execution tag. The execution is only used when your plug-in is triggered by a special phase of the complete Maven build.
The Maven guide to configuration explains it better:
Configurations inside the tag differ from those that are outside in that they cannot be used from a direct command line invocation. Instead they are only applied when the lifecycle phase they are bound to are invoked. Alternatively, if you move a configuration section outside of the executions section, it will apply globally to all invocations of the plugin.

Try this, moving the configuration outside executions, so it isn't bound to the life cycle phase.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.0.1</version>
<executions>
<execution>
<id>enforce-versions</id>
<goals>
<goal>enforce</goal>
</goals>
</execution>
</executions>
<configuration>
<rules>
<AlwaysPass />
</rules>
<fail>true</fail>
</configuration>
</plugin>
Now when you do mvn enforcer:enforce, it picks the rules from your pom.xml.

See these answers
You can use the special default command line execution id, default-cli to invoke it (see Maven Docs), see my example below. This works at least with 3.1.1 and the article cited says it should work with 2.2.0+
mvn enforcer:enforce
However if you are using above Maven 3.1.1 (I can confirm it works in 3.3.3 with enforcer v 1.4.1) you can specify the execution id you wish using the new # syntax (see Maven JIRA and the answers above);
e.g. for the example below use
mvn enforcer:enforce#dependency-convergence
Here's a snippet from my pom;
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.4.1</version>
<executions>
<execution>
<id>dependency-convergence</id>
<phase>install</phase>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<DependencyConvergence />
</rules>
<fail>true</fail>
</configuration>
</execution>
<execution>
<id>default-cli</id>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<DependencyConvergence/>
</rules>
<fail>true</fail>
</configuration>
</execution>
</executions>
</plugin>
...

I don't know why it won't work with the config being in an execution, but this worked for me:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.0</version>
<configuration>
<rules>
<banDuplicateClasses>
<findAllDuplicates>true</findAllDuplicates>
</banDuplicateClasses>
</rules>
<fail>false</fail>
</configuration>
<dependencies>
<dependency>
<groupId>org.codehaus.mojo</groupId>
<artifactId>extra-enforcer-rules</artifactId>
<version>1.0-alpha-1</version>
</dependency>
</dependencies>
</plugin>