What are the phases of the maven clean lifecycle?

Maven Clean Lifecycle Phases

    pre-clean
    clean
    post-clean

Calling one phase of the clean lifecycle results in the execution of all phases up to an including that phase. So, if we perform a "mvn clean", we will execute the pre-clean and the clean phases. If we perform a "mvn post-clean", we will execute the pre-clean, clean, and post-clean phases.

The maven "clean:clean" goal is typically bound to the clean phase. This goal 'cleans' the project's build (usually 'target') directory, which typically involves deleting old files. The pre-clean phase can be used for any tasks required prior to cleanup, and the post-clean phase can be used for tasks following the cleanup.

We can bind other goals to the phases of the clean lifecycle. In the following pom.xml file, I bind the maven-antrun-plugin:run goal to the pre-clean, clean, and post-clean phases. This will allow me to echo text messages displaying the phases of the clean lifecycle.
pom.xml file that binds antrun:run to pre-clean, clean, and post-clean phases

<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/maven-v4_0_0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.maventest</groupId>
	<artifactId>aproject</artifactId>
	<packaging>pom</packaging>
	<version>1.0-SNAPSHOT</version>
	<name>aproject</name>
	<url>http://maven.apache.org</url>
	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>3.8.1</version>
			<scope>test</scope>
		</dependency>
	</dependencies>
	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-antrun-plugin</artifactId>
				<version>1.1</version>
				<executions>
					<execution>
						<id>id.pre-clean</id>
						<phase>pre-clean</phase>
						<goals>
							<goal>run</goal>
						</goals>
						<configuration>
							<tasks>
								<echo>in pre-clean phase</echo>
							</tasks>
						</configuration>
					</execution>
					<execution>
						<id>id.clean</id>
						<phase>clean</phase>
						<goals>
							<goal>run</goal>
						</goals>
						<configuration>
							<tasks>
								<echo>in clean phase</echo>
							</tasks>
						</configuration>
					</execution>
					<execution>
						<id>id.post-clean</id>
						<phase>post-clean</phase>
						<goals>
							<goal>run</goal>
						</goals>
						<configuration>
							<tasks>
								<echo>in post-clean phase</echo>
							</tasks>
						</configuration>
					</execution>
				</executions>
			</plugin>
		</plugins>
	</build>
</project>

If we perform a "mvn clean" on the project with the above pom.xml, we can see that the pre-clean and clean phases are executed based on our text messages.
Console output from 'mvn clean'

[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building aproject
[INFO]    task-segment: [clean]
[INFO] ------------------------------------------------------------------------
[INFO] [antrun:run {execution: id.pre-clean}]
[INFO] Executing tasks
     [echo] in pre-clean phase
[INFO] Executed tasks
[INFO] [clean:clean]
[INFO] Deleting directory C:\dev\workspace\aproject\target
[INFO] [antrun:run {execution: id.clean}]
[INFO] Executing tasks
     [echo] in clean phase
[INFO] Executed tasks
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1 second
[INFO] Finished at: Wed Feb 13 14:44:26 PST 2008
[INFO] Final Memory: 3M/7M
[INFO] ------------------------------------------------------------------------

If we perform a "mvn post-clean" on the project, we can see that the pre-clean, clean, and post-clean phases are all executed.
Console output from 'mvn post-clean'

[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building aproject
[INFO]    task-segment: [post-clean]
[INFO] ------------------------------------------------------------------------
[INFO] [antrun:run {execution: id.pre-clean}]
[INFO] Executing tasks
     [echo] in pre-clean phase
[INFO] Executed tasks
[INFO] [clean:clean]
[INFO] Deleting directory C:\dev\workspace\aproject\target
[INFO] [antrun:run {execution: id.clean}]
[INFO] Executing tasks
     [echo] in clean phase
[INFO] Executed tasks
[INFO] [antrun:run {execution: id.post-clean}]
[INFO] Executing tasks
     [echo] in post-clean phase
[INFO] Executed tasks
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1 second
[INFO] Finished at: Wed Feb 13 14:44:55 PST 2008
[INFO] Final Memory: 3M/6M
[INFO] ------------------------------------------------------------------------