❮ Maven Build Test Project Maven Tutorial ❯

Maven Plugins

Maven has the following three standard lifecycles:

clean: Handles project cleaning
default (or build): Handles project deployment
site: Handles project site documentation creation

Each lifecycle contains a series of phases. These phases serve as unified interfaces provided by Maven, and their implementations are completed by Maven plugins.

When we input a Maven command, such as mvn clean, clean corresponds to the clean phase in the Clean lifecycle. However, the specific operations of clean are implemented by the maven-clean-plugin.

Therefore, the implementation of each phase in the Maven lifecycle is accomplished by Maven plugins.

Maven is essentially a framework that relies on plugins to execute, with each task being completed by a plugin. Maven plugins are commonly used for:

Creating jar files
Creating war files
Compiling code files
Unit testing code
Creating project documentation
Creating project reports

Plugins typically offer a collection of goals and can be executed using the following syntax:

mvn [plugin-name]:[goal-name]

For example, a Java project can be compiled using the compile-goal of the maven-compiler-plugin with the following command:

mvn compiler:compile

Plugin Types

Maven provides the following two types of plugins:

Type	Description
Build plugins	Execute during the build and are configured in the `pom.xml` under the `<build>` element.
Reporting plugins	Execute during the site generation and are configured in the `pom.xml` under the `<reporting>` element.

Below is a list of some commonly used plugins:

Plugin	Description
clean	Cleans up target files after the build. Deletes the target directory.
compiler	Compiles Java source files.
surefire	Runs JUnit unit tests. Creates test reports.
jar	Builds a JAR file from the current project.
war	Builds a WAR file from the current project.
javadoc	Generates Javadoc for the project.
antrun	Runs a set of Ant tasks from any phase in the build process.

Example

We have extensively used the maven-antrun-plugin in our examples to output data to the console. Please refer to the Maven - Build Profiles section. Let's understand this better by creating a pom.xml file in the C:\MVN\project directory.

&lt;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>com.companyname.projectgroup</groupId>
<artifactId>project</artifactId>
<version>1.0</version>
<build>
<plugins>
   <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-antrun-plugin</artifactId>
   <version>1.1</version>
   <executions>
      <execution>
         <id>id.clean</id>
         <phase>clean</phase>
         <goals>
            <goal>run</goal>
         </goals>
         <configuration>
            <tasks>
               <echo>clean phase</echo>
            </tasks>
         </configuration>
      </execution>     
   </executions>

</plugin>
</plugins>
</build>
</project>

Next, open the command terminal, navigate to the directory containing the pom.xml file, and execute the following mvn command.

mvn clean

Maven will start processing and display the clean phase of the clean lifecycle.

[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------
[INFO] Building Unnamed - com.companyname.projectgroup:project:jar:1.0
[INFO]    task-segment: [post-clean]
[INFO] ------------------------------------------------------------------
[INFO] [clean:clean {execution: default-clean}]
[INFO] [antrun:run {execution: id.clean}]
[INFO] Executing tasks
     [echo] clean phase
[INFO] Executed tasks
[INFO] ------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------
[INFO] Total time: < 1 second
[INFO] Finished at: Sat Jul 07 13:38:59 IST 2012
[INFO] Final Memory: 4M/44M
[INFO] ------------------------------------------------------------------

The example above illustrates the following key concepts:

Plugins are defined using the plugins element in pom.xml.
Each plugin can have multiple goals.
You can define phases, and the plugin will start processing using its phase element. We have used the clean phase.
You can configure tasks to be executed by binding them to the plugin's goals. We have bound the echo task to the run goal of the maven-antrun-plugin.
That's it; Maven will handle the rest. It will download the plugins not available in the local repository and begin processing.

❮ Maven Build Test Project Maven Tutorial ❯