How To Reuse Java EE 6 WAR Code With Maven (3)
In Java EE 6 WAR is the new EAR. A WAR, however, is entirely "installed" to the maven 3 repo. It's contents (like JAXB-DTOs), cannot be reused from other applications.
Configuration of maven-jar-plugin and maven-install-plugin solves the issue. The first plugin creates a JAR and the latter installs it into the local repo:
...
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<executions>
<execution>
<id>make-jar</id>
<phase>compile</phase>
<goals>
<goal>jar</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-install-plugin</artifactId>
<executions>
<execution>
<id>install-jar</id>
<phase>install</phase>
<goals>
<goal>install-file</goal>
</goals>
<configuration>
<packaging>jar</packaging>
<artifactId>${project.artifactId}</artifactId>
<groupId>${project.groupId}</groupId>
<version>${project.version}</version>
<file>${project.build.directory}/${project.build.finalName}.jar</file>
</configuration>
</execution>
</executions>
</plugin>
...
</plugins>
After configuration of both plugins, WAR contents are redundantly stored as JAR in the local maven repository and are accessible to other projects by specifying a "usual" dependency to it.
You could also use the attachClasses tag to deploy the jar in addition to the WAR with the "classes" classifier (as suggested by struberg):
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.1.1</version>
<configuration>
<attachClasses>true</attachClasses>
But then you will also have to specify the classifier in the dependency:
<dependency>
<groupId>...</groupId>
<artifactId>...</artifactId>
<version>...</version>
<classifier>classes</classifier>
<scope>test</scope>
</dependency>
While this is possible the better practice is to have a normal (jar) project for your code and have a separate project that builds the war file. Typically you will split any real world project into several projects anyway.
Posted by Christian Schneider on June 10, 2011 at 02:27 PM CEST #
why so complicated?
just tell the maven-war-plugin [1] to
<configuration>
<attachClasses>true</attachClasses>
<archiveClasses>true</archiveClasses>
</configuration>
This will package all classes which would normally land in WEB-INF/classes as separate jar and serve it as 'attached artifact' [2]. You can then reference this 'attached artifact' as normal dependency by just using the proper <classifier> in your targets<dependency> section.
LieGrue,
strub
[1] http://maven.apache.org/plugins/maven-war-plugin/war-mojo.html
[2] http://docs.codehaus.org/display/MAVEN/Packaging+vs+Type+-+Derived+and+Attached+Artifacts
LieGrue,
strub
Posted by struberg on June 10, 2011 at 03:14 PM CEST #
Hi Adam
For me, your proposal looks like a fight against Maven. If some part of the application is needed outside, put it into separate Maven module.
WAR packaging does not mean that you can not modularize application :-)
Posted by Marcin on June 10, 2011 at 03:42 PM CEST #
@Christian,
"...Typically you will split any real world project into several projects anyway."
As described here: http://www.adam-bien.com/roller/abien/entry/is_java_ee_6_war
In this case I do not want any additional JARs or modules and would like to keep everything in one place.
But you are right: in most of my projects we have multiple JARs linked to a single WAR.
thanks!,
adam
Posted by Adam Bien on June 10, 2011 at 07:38 PM CEST #
@Struberg,
attachClasses is a good point -> it made my post longer :-).
thanks!,
adam
Posted by Adam Bien on June 10, 2011 at 07:39 PM CEST #
@Marcin,
"For me, your proposal looks like a fight against Maven"
In this case I only need a few classes for a system test. It is a corner case. If the content were more interesting for other applications I would externalize them as described here: http://www.adam-bien.com/roller/abien/entry/is_java_ee_6_war
Thanks for your comment!,
adam
Posted by Adam Bien on June 10, 2011 at 07:41 PM CEST #