maven 2.2 war build does not put classes in associated *-classes.jar file

Question

I'm trying to build a (war) project where I copied and modifed the pom.xml file from another piece of code, and for some reason when I mvn clean package the software it doesn't include the classes into the associated *-classes.jar file. Maven version is 2.2.1 on Ubuntu 12.10.

I'm highly novice in maven, and largely manage by copy-and-paste from examples, so I basically have no idea how my pom works (it is included in full below).

The project has a <packaging>war</packaging> element, and the maven-war-plugin configuration section says to archiveClasses and attachClasses, which I presume is what causes the *-classes.jar file to be built. Once I've run the build, my target directory looks as follows:

richard@holly:~/Code/External/JavaServer2.0/target$ ls 
apidocs  generated-sources  surefire           sword2-server-1.0-classes.jar  sword2-server-1.0-sources.jar
classes  maven-archiver     sword2-server-1.0  sword2-server-1.0-javadoc.jar  sword2-server-1.0.war

But the sword2-server-1.0-classes.jar doesn't contain any of the classes:

richard@holly:~/Code/External/JavaServer2.0/target$ jar tf sword2-server-1.0-classes.jar
META-INF/
META-INF/MANIFEST.MF
META-INF/maven/
META-INF/maven/org.swordapp/
META-INF/maven/org.swordapp/sword2-server/
META-INF/maven/org.swordapp/sword2-server/pom.xml
META-INF/maven/org.swordapp/sword2-server/pom.properties

Meanwhile all the other *.jar files in this directory contain all the relevant information for the source files (javadocs, source, etc, are all complete).

I'm no doubt missing some form of plugin configuration, but am so far unable to make any sense of the maven plugin documentation, so any help hugely appreciated.

The (nearly) full pom.xml (omitted the actual dependencies for brevity):

<?xml version="1.0" encoding="UTF-8"?>
<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>org.swordapp</groupId>
<artifactId>sword2-server</artifactId>
<version>1.0</version>
<packaging>war</packaging>

<name>SWORD v2 :: Common Server Library</name>
<description>
    Common Server Library with interfaces to be implemented by servers
    wishing to provide SWORD v2 support
</description>
<url>http://www.swordapp.org/</url>

<build>
    <plugins>
        <plugin>
            <artifactId>maven-release-plugin</artifactId>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>2.3.2</version>
            <configuration>
                <source>6</source>
                <target>6</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
                <archive>
                    <manifest>
                        <addDefaultImplementationEntries>
                            true
                        </addDefaultImplementationEntries>
                        <addDefaultSpecificationEntries>
                            true
                        </addDefaultSpecificationEntries>
                    </manifest>
                </archive>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-source-plugin</artifactId>
            <executions>
                <execution>
                    <id>default</id>
                    <phase>package</phase>
                    <goals>
                        <goal>jar</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-javadoc-plugin</artifactId>
            <executions>
                <execution>
                    <id>default</id>
                    <phase>package</phase>
                    <goals>
                        <goal>jar</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <configuration>
                <archiveClasses>true</archiveClasses>
                <attachClasses>true</attachClasses>
                <packagingExcludes>WEB-INF/lib/*.jar</packagingExcludes>
                <warSourceExcludes>WEB-INF/lib/*.jar</warSourceExcludes>
                <webResources>
                    <resource>
                        <filtering>true</filtering>
                        <directory>${basedir}/src/main/webapp</directory>
                        <includes>
                            <include>WEB-INF/web.xml</include>
                        </includes>
                    </resource>
                </webResources>
            </configuration>
            <executions>
                <execution>
                    <phase>prepare-package</phase>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

<dependencies>
    ....
</dependencies>
</project>

Answer 1

It turns out that archiveClasses and attachClasses don't play well together. The documentation for attachClasses says that it will put the files in the webapps classes directory into a *-classes.jar during the war build. But archiveClasses places the content of the classes directory in the webapp into a jar file in the webapp's lib directory. Since this means that there are no classes in the classes directory to be put into the *-classes.jar if both these configuration flags are set to true.

The answer is to remove archiveClasses from the configuration, and then everything behaves as expected.

This seems like it's probably a maven bug, and it behaves the same in both maven 2 and maven 3.

Answer 2

You should try to boil down the problem by reducing the complexity just try a simple configuration as follows first:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-war-plugin</artifactId>
    <configuration>
        <archiveClasses>true</archiveClasses>
        <attachClasses>true</attachClasses>
    </configuration>
</plugin>

After that just try:

mvn clean package