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November 18, 2022 08:21 am GMT

Create a Simple Maven Plugin

Summary

In this post I'll demonstrate how quickly a simple Maven plugin can be created.

Reason

Normally in Maven project you do not need to create own plugins as there likely exists a plugin which covers common scenarios. However, there are edge cases or project specific needs where having own plugin would make sense.

What do we need

  • Installed Maven (I used 3.6.3)
  • Java 11+ (for lower Java version sample POM needs to be adjusted)
  • Your favorite text editor

Naming

Every project starts from its name. The plugin naming convention is <yourplugin>-maven-plugin. In sample I'll use struggzard-maven-plugin.

Project POM

Create project directory struggzard-maven-plugin and add pom.xml file with content bellow:

<project>    <modelVersion>4.0.0</modelVersion>    <groupId>dev.stuggzard.tutorial</groupId>    <artifactId>struggzard-maven-plugin</artifactId>    <version>1.0-SNAPSHOT</version>    <packaging>maven-plugin</packaging>    <name>A Simple Maven Plugin</name>    <properties>        <java.version>11</java.version>        <maven.compiler.source>${java.version}</maven.compiler.source>        <maven.compiler.target>${java.version}</maven.compiler.target>    </properties>    <dependencies>        <dependency>            <groupId>org.apache.maven</groupId>            <artifactId>maven-plugin-api</artifactId>            <version>3.0</version>        </dependency>        <!-- dependencies to annotations -->        <dependency>            <groupId>org.apache.maven.plugin-tools</groupId>            <artifactId>maven-plugin-annotations</artifactId>            <version>3.4</version>            <scope>provided</scope>        </dependency>    </dependencies></project>

At this point maven build will likely fail as there no Mojo defined.

Add Mojo

The "Mojo" in Maven terminology is a simple class which represents one plugin goal (e.g. print message).

package dev.struggzard.tutorial;import org.apache.maven.plugin.AbstractMojo;import org.apache.maven.plugin.MojoExecutionException;import org.apache.maven.plugin.MojoFailureException;import org.apache.maven.plugins.annotations.Mojo;import org.apache.maven.plugins.annotations.Parameter;/** * A Mojo which accepts parameter and prints it. */@Mojo(name = "print")public class MessagePrinterMojo extends AbstractMojo {    @Parameter( property = "print.text", defaultValue = "Default text" )    private String textParameter;    public void execute() throws MojoExecutionException, MojoFailureException {        getLog().info(textParameter);    }}

Running from CLI

Maven plugin can be invoked directly from CLI using following pattern:
mvn groupId:artifactId:version:goal

Run plugin:
mvn dev.stuggzard.tutorial:struggzard-maven-plugin:1.0-SNAPSHOT:print

Output:

[INFO] Scanning for projects...[INFO] [INFO] ---< dev.stuggzard.tutorial:struggzard-maven-plugin >---[INFO] Building A Simple Maven Plugin 1.0-SNAPSHOT[INFO] ---[ maven-plugin ]---[INFO] [INFO] --- struggzard-maven-plugin:1.0-SNAPSHOT:print (default-cli) @ struggzard-maven-plugin ---[INFO] Default text[INFO] -----------------------------------------------------------------------[INFO] BUILD SUCCESS[INFO] -----------------------------------------------------------------------[INFO] Total time:  0.390 s[INFO] Finished at: 2020-06-21T17:29:28+03:00[INFO] ------------------------------------------------------------------------

As no parameter was passed [INFO] Default text was printed.

Now try passing text parameter:
mvn dev.stuggzard.tutorial:struggzard-maven-plugin:1.0-SNAPSHOT:print -"Dprint.text=Sample Text"

Output:

[INFO] Scanning for projects...[INFO] [INFO] ---< dev.stuggzard.tutorial:struggzard-maven-plugin >---[INFO] Building A Simple Maven Plugin 1.0-SNAPSHOT[INFO] ---[ maven-plugin ]---[INFO] [INFO] --- struggzard-maven-plugin:1.0-SNAPSHOT:print (default-cli) @ struggzard-maven-plugin ---[INFO] Sample Text[INFO] ------------------------------------------------------------------------[INFO] BUILD SUCCESS[INFO] ------------------------------------------------------------------------[INFO] Total time:  0.346 s[INFO] Finished at: 2020-06-21T17:33:08+03:00[INFO] ------------------------------------------------------------------------

With passed parameter text was printed accordingly [INFO] Sample Text.

Adding plugin in other Maven project

In most cases plugins are created for integration into another maven project. Here some sample Maven project POM:

<project>    <modelVersion>4.0.0</modelVersion>    <groupId>dev.struggzard.tutorial</groupId>    <artifactId>sample-module</artifactId>    <version>1</version>    <properties>        <java.version>11</java.version>        <maven.compiler.source>${java.version}</maven.compiler.source>        <maven.compiler.target>${java.version}</maven.compiler.target>    </properties>    <build>        <plugins>            <plugin>                <groupId>dev.stuggzard.tutorial</groupId>                <artifactId>struggzard-maven-plugin</artifactId>                <version>1.0-SNAPSHOT</version>                <executions>                    <execution>                        <phase>validate</phase>                        <goals>                            <goal>print</goal>                        </goals>                    </execution>                </executions>                <configuration>                    <textParameter>Sample text</textParameter>                </configuration>            </plugin>        </plugins>    </build></project>

By invoking mvn clean install on maven project Maven plugin goal print will be triggered with configured text parameter.

Resources


Original Link: https://dev.to/struggzard/create-a-simple-maven-plugin-6gf

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