Maven models projects as nouns which are described by a POM. The POM captures the identity of a project: What does a project contain? What type of packaging a project needs? Does the project have a parent? What are the dependencies? We’ve explored the idea of describing a project in the previous chapters, but we haven’t introduced the mechanism that allows Maven to act upon these objects. In Maven the "verbs" are goals packaged in Maven plugins which are tied to a phases in a build lifecycle. A Maven lifecycle consists of a sequence of named phases: prepare-resources, compile, package, and install among other. There is phase that captures compilation and a phase that captures packaging. There are pre- and post- phases which can be used to register goals which must run prior to compilation, or tasks which must be run after a particular phase. When you tell Maven to build a project, you are telling Maven to step through a defined sequence of phases and execute any goals which may have been registered with each phase.
A build lifecycle is an organized sequence of phases that exist to give order to a set of goals. Those goals are chosen and bound by the packaging type of the project being acted upon. There are three standard lifecycles in Maven: clean, default (sometimes called build) and site. In this chapter, you are going to learn how Maven ties goals to lifecycle phases and how the lifecycle can be customized. You will also learn about the default lifecycle phases.
The first lifecycle you’ll be interested in is the simplest lifecycle in Maven. Running mvn clean invokes the clean lifecycle which consists of three lifecycle phases:
-
pre-clean
-
clean
-
post-clean
The interesting phase in the clean lifecycle is the clean phase. The Clean plugin’s clean goal (clean:clean) is bound to the clean phase in the clean lifecycle. The clean:clean goal deletes the output of a build by deleting the build directory. If you haven’t customized the location of the build directory it will be the '${basedir}/target' directory as defined by the Super POM. When you execute the clean:clean goal you do not do so by executing the goal directly with mvn clean:clean, you do so by executing the clean phase of the clean lifecycle. Executing the clean phase gives Maven an opportunity to execute any other goals which may be bound to the pre-clean phase.
For example, suppose you wanted to trigger an antrun:run goal task to echo a notification on pre-clean, or to make an archive of a project’s build directory before it is deleted. Simply running the clean:clean goal will not execute the lifecycle at all, but specifying the clean phase will use the clean lifecycle and advance through the three lifecycle phases until it reaches the clean phase. Triggering a Goal on pre-clean shows an example of build configuration which binds the antrun:run goal to the pre-clean phase to echo an alert that the project artifact is about to be deleted. In this example, the antrun:run goal is being used to execute some arbitrary Ant commands to check for an existing project artifact. If the project’s artifact is about to be deleted it will print this to the screen
<project>
...
<build>
<plugins>... <plugin>
<artifactId>maven-antrun-plugin</artifactId>
<executions>
<execution>
<id>file-exists</id>
<phase>pre-clean</phase>
<goals>
<goal>run</goal>
</goals>
<configuration>
<tasks>
<!-- adds the ant-contrib tasks (if/then/else used below) -->
<taskdef resource="net/sf/antcontrib/antcontrib.properties" />
<available
file="${project.build.directory}/${project.build.finalName}.${project.packaging}"
property="file.exists" value="true" />
<if>
<not>
<isset property="file.exists" />
</not>
<then>
<echo>No
${project.build.finalName}.${project.packaging} to
delete</echo>
</then>
<else>
<echo>Deleting
${project.build.finalName}.${project.packaging}</echo>
</else>
</if>
</tasks>
</configuration>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>ant-contrib</groupId>
<artifactId>ant-contrib</artifactId>
<version>1.0b2</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
</project>
Running mvn clean on a project with this build configuration will produce output similar to the following:
[INFO] Scanning for projects...
[INFO] ----------------------------------------------------------------------
[INFO] Building Your Project
[INFO]task-segment: [clean]
[INFO] ----------------------------------------------------------------------
[INFO] [antrun:run {execution: file-exists}]
[INFO] Executing tasks
[echo] Deleting your-project-1.0-SNAPSHOT.jar
[INFO] Executed tasks
[INFO] [clean:clean]
[INFO] Deleting directory ~/corp/your-project/target
[INFO] Deleting directory ~/corp/your-project/target/classes
[INFO] Deleting directory ~/corp/your-project/target/test-classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1 second
[INFO] Finished at: Wed Nov 08 11:46:26 CST 2006
[INFO] Final Memory: 2M/5M
[INFO] ------------------------------------------------------------------------
In addition to configuring Maven to run a goal during the pre-clean phase, you can also customize the Clean plugin to delete files in addition to the build output directory. You can configure the plugin to remove specific files in a fileSet. The example below configures clean to remove all '.class' files in a directory named 'target-other/' using standard Ant file wildcards: \* and \**.
<project>
<modelVersion>4.0.0</modelVersion>
...
<build>
<plugins>
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<configuration>
<filesets>
<fileset>
<directory>target-other</directory>
<includes>
<include>*.class</include>
</includes>
</fileset>
</filesets>
</configuration>
</plugin>
</plugins>
</build>
</project>
Most Maven users will be familiar with the default lifecycle. It is a general model of a build process for a software application. The first phase is validate and the last phase is deploy. The phases in the default Maven lifecycle are shown in Maven Lifecycle Phases.
| Lifecycle Phase | Description |
|---|---|
validate |
Validate the project is correct and all necessary information is available to complete a build |
generate-sources |
Generate any source code for inclusion in compilation |
process-sources |
Process the source code, for example to filter any values |
generate-resources |
Generate resources for inclusion in the package |
process-resources |
Copy and process the resources into the destination directory, ready for packaging |
compile |
Compile the source code of the project |
process-classes |
Post-process the generated files from compilation, for example to do bytecode enhancement on Java classes |
generate-test-sources |
Generate any test source code for inclusion in compilation |
process-test-sources |
Process the test source code, for example to filter any values |
generate-test-resources |
Create resources for testing |
process-test-resources |
Copy and process the resources into the test destination directory |
test-compile |
Compile the test source code into the test destination directory |
test |
Run tests using a suitable unit testing framework. These tests should not require the code be packaged or deployed |
prepare-package |
Perform any operations necessary to prepare a package before the actual packaging. This often results in an unpacked, processed version of the package (coming in Maven 2.1+) |
package |
Take the compiled code and package it in its distributable format, such as a JAR, WAR, or EAR |
pre-integration-test |
Perform actions required before integration tests are executed. This may involve things such as setting up the required environment |
integration-test |
Process and deploy the package if necessary into an environment where integration tests can be run |
post-integration-test |
Perform actions required after integration tests have been executed. This may include cleaning up the environment |
verify |
Run any checks to verify the package is valid and meets quality criteria |
install |
Install the package into the local repository, for use as a dependency in other projects locally |
deploy |
Copies the final package to the remote repository for sharing with other developers and projects (usually only relevant during a formal release) |
======================== Maven does more than build software artifacts from project, it can also generate project documentation and reports about the project, or a collection of projects. Project documentation and site generation have a dedicated lifecycle which contains four phases: . pre-site . site . post-site . site-deploy The default goals bound to the site lifecycle is: . site - site:site . site-deploy -site:deploy The packaging type does not usually alter this lifecycle since packaging types are concerned primarily with artifact creation, not with the type of site generated. The Site plugin kicks off the execution of Doxia document generation and other report generation plugins. You can generate a site from a Maven project by running the following command: ---- $ mvn site ---- For more information about Maven Site generation, see [site-generation]. === Package-specific Lifecycles The specific goals bound to each phase default to a set of goals specific to a project’s packaging. A project with packaging jar has a different set of default goals from a project with a packaging of war. The packaging element affects the steps required to build a project. For an example of how the packaging affects the build, consider two projects: one with pom packaging and the other with jar packaging. The project with pom packaging will run the site:attach-descriptor goal during the package phase, and the project with jar packaging will run the jar:jar goal instead. The following sections describe the lifecycle for all built-in packaging types in Maven. Use these sections to find out what default goals are mapped to default lifecycle phases. JAR is the default packaging type, the most common, and thus the most commonly encountered lifecycle configuration. The default goals for the JAR lifecycle are shown in [tbl-jar-lifecycle]. |
=============================== |
Lifecycle Phase |
Goal |
process-resources |
resources:resources |
compile |
compiler:compile |
process-test-resources |
resources:testResources |
test-compile |
compiler:testCompile |
test |
surefire:test |
package |
jar:jar |
install |
install:install |
deploy |
deploy:deploy |
=============================== POM is the simplest packaging type. The artifact that it generates is itself only, rather than a JAR, SAR, or EAR. There is no code to test or compile, and there are no resources the process. The default goals for projects with POM packaging are shown in [tbl-pom-lifecycle]. |
=============================== |
Lifecycle Phase |
Goal |
package |
site:attach-descriptor |
install |
install:install |
deploy |
deploy:deploy |
========================= This packaging type is similar to JAR packaging type with three additions: plugin:descriptor, plugin:addPluginArtifactMetadata, and plugin:updateRegistry. These goals generate a descriptor file and perform some modifications to the repository data. The default goals for projects with plugin packaging are shown in [tbl-plugin-lifecycle]. |
======================== |
Lifecycle Phase |
Goal |
generate-resources |
plugin:descriptor |
process-resources |
resources:resources |
compile |
compiler:compile |
process-test-resources |
resources:testResources |
test-compile |
compiler:testCompile |
test |
surefire:test |
package |
jar:jar, plugin:addPluginArtifactMetadata |
install |
install:install, plugin:updateRegistry |
deploy |
deploy:deploy |
========================= EJBs, or Enterprise Java Beans, are a common data access mechanism for model-driven development in Enterprise Java. Maven provides support for EJB 2 and 3. Though you must configure the EJB plugin to specifically package for EJB3, else the plugin defaults to 2.1 and looks for the presence of certain EJB configuration files. The default goals for projects with EJB packaging are shown in [tbl-ejb-lifecycle]. |
=============================== |
Lifecycle Phase |
Goal |
process-resources |
resources:resources |
compile |
compiler:compile |
process-test-resources |
resources:testResources |
test-compile |
compiler:testCompile |
test |
surefire:test |
package |
ejb:ejb |
install |
install:install |
deploy |
deploy:deploy |
========================= The WAR packaging type is similar to the JAR and EJB types. The exception being the package goal of war:war. Note that the war:war goal requires a 'web.xml' configuration in your 'src/main/webapp/WEB-INF' directory. The default goals for projects with WAR packaging are shown in [tbl-war-lifecycle]. |
=============================== |
Lifecycle Phase |
Goal |
process-resources |
resources:resources |
compile |
compiler:compile |
process-test-resources |
resources:testResources |
test-compile |
compiler:testCompile |
test |
surefire:test |
package |
war:war |
install |
install:install |
deploy |
deploy:deploy |
=============================== EARs are probably the simplest Java EE constructs, consisting primarily of the deployment descriptor 'application.xml' file, some resources and some modules. The EAR plugin has a goal named generate-application-xml which generates the 'application.xml' based upon the configuration in the EAR project’s POM. The default goals for projects with EAR packaging are shown in [tbl-ear-lifecycle]. |
========================= |
Lifecycle Phase |
Goal |
generate-resources |
ear:generate-application-xml |
process-resources |
resources:resources |
package |
ear:ear |
install |
install:install |
deploy |
deploy:deploy |
========================= This is not an exhaustive list of every packaging type available for Maven. There are a number of packaging formats available through external projects and plugins: the NAR (native archive) packaging type, the SWF and SWC packaging types for projects that produce Adobe Flash and Flex content, and many others. You can also define a custom packaging type and customize the default lifecycle goals to suit your own project packaging requirements. To use one of these custom packaging types, you need two things: a plugin which defines the lifecycle for a custom packaging type and a repository which contains this plugin. Some custom packaging types are defined in plugins available from the central Maven repository. Here is an example of a project which references the Israfil Flex plugin and uses a custom packaging type of SWF to produce output from Adobe Flex source. .Custom Packaging Type for Adobe Flex (SWF) ---- <project> … <packaging>swf</packaging> … <build> <plugins> <plugin> <groupId>net.israfil.mojo</groupId> <artifactId>maven-flex2-plugin</artifactId> <version>1.4-SNAPSHOT</version> <extensions>true</extensions> <configuration> <debug>true</debug> <flexHome>${flex.home}</flexHome> <useNetwork>true</useNetwork> <main>org/sonatype/mavenbook/Main.mxml</main> </configuration> </plugin> </plugins> </build> … </project> ---- In [writing-plugins-sect-plugins-lifecycle], we show you how to create your own packaging type with a customized lifecycle. This example should give you an idea of what you’ll need to do to reference a custom packaging type. All you need to do is reference the plugin which supplies the custom packaging type. The Israfil Flex plugin is a third-party Maven plugin hosted at Google Code, for more information about this plugin and how to use Maven to compile Adobe Flex go to http://code.google.com/p/israfil-mojo. This plugin supplies the following lifecycle for the SWF packaging type: .Default Lifecycle for SWF Packaging |
========================= |
Lifecycle Phase |
Goal |
compile |
flex2:compile-swc |
install |
install:install |
deploy |
deploy:deploy |