Maven Plugin

Maven has the following three standard lifecycles:

• clean: Project cleanup processing

• default( or build): Project deployment processing

• site: Project site document creation processing

Each lifecycle contains a series of phases (phases). These phases are equivalent to the unified interfaces provided by Maven, and the implementation of these phases is completed by Maven plugins.

When we enter the mvn command, for example mvn clean, clean corresponds to the clean phase of the Clean lifecycle. However, the specific operation of clean is by maven-clean-plugin to implement.

Therefore, the specific implementation of each stage of the Maven lifecycle is actually implemented by Maven plugins.

Maven is actually a framework that executes dependency plugins, and each task is actually completed by plugins. Maven plugins are usually used for:

• Create jar file

• Create war file

• Compile code files

• Code unit test

• Create project documentation

• Create project report

Plugins usually provide a set of goals and can be executed using the following syntax:

<code>mvn [plugin-name]:[goal-name]/code>

For example, a Java project can use maven-compiler-compile goal of the plugin-goal Compile, use the following command:

<code>mvn compiler:compile</code>

Plugin types

Maven provides the following two types of plugins:

Below is a list of some commonly used plugins:

Online examples

We have used it extensively in our example maven-antrun-plugin to output data to the console. Please see Maven - Build configuration file Let's understand this section in a better way. Create a pom.xml file in the C:\MVN\project directory.

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

Next, open the command terminal and navigate to the directory where pom.xml is located, 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-}]
[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 above example demonstrates 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 clean phase.

• You can configure the task to be executed by binding it to the target of the plugin. We have bound echo task to maven-antrun-of the plugin run Target.

• That's it, Maven will handle the rest. It will download plugins that are not available in the local repository and start processing.