Maven assembly plugin produces undeployable war file - deployment

Question

I'm working on a multi module project using Spring, Hibernate, GWT and Maven 3 and try to deploy a war-file distribution to a servlet container (preferably Tomcat 7 or Jetty 8). I create the war-file using maven-assembly-plugin 2.2.1 (I'm running maven 3). During the maven build everything works perfectly and the distribution archive is created.
But when I try to deploy the war file, I get ClassNotFound-Exceptions (e.g. Spring ContextLoaderListener and the like) although everything is in place (Web-inf/lib etc. pp.). So, the webapp isn't starting. Then I unpack the war-file into the servlet containers webapp directory and everything is working fine... ??
After further investigation I came across the following thing:
If I take an arbitrary war file A' created by maven-war-plugin (!), replace its content with the unpacked content from the war file I created using maven-assembly-plugin (let me call it
A.) I can see two things happen:
the resulting war file A' is a few bytes smaller than my original file A although their content is identical
the deployment of A' suddenly works like a charm
This is weird and I have absolutely no idea what's happening. Maybe there is an issue and maven-war-plugin and maven-assembly-plugin handle war file packaging differently?! I mean, a war is only a renamed zip file with some predefined structure... Maybe it has absolutely nothing to do with maven but with file encoding or other things? Any ideas on this? I appreciate any hint, that could help me in investigating this...
This is my assembly descriptor
<assembly
xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2 http://maven.apache.org/xsd/assembly-1.1.2.xsd">
<id>dist</id>
<formats>
<format>war</format>
</formats>
<includeBaseDirectory>false</includeBaseDirectory>
<dependencySets>
<dependencySet>
<unpack>true</unpack>
<includes>
<include>mypackage.client:parametermgmt:*</include>
<include>mypackage.static:client:*</include>
</includes>
<useProjectArtifact>false</useProjectArtifact>
<outputDirectory>/</outputDirectory>
</dependencySet>
<dependencySet>
<unpack>false</unpack>
<includes>
<include>mypackage.server.database:domain:*</include>
<include>mypackage.server.businessobjects:BOdomain:*</include>
<include>mypackage.server.security:security:*</include>
<include>mypackage.server.services:paramgmt:*</include>
</includes>
<useProjectArtifact>false</useProjectArtifact>
<outputDirectory>Web-inf/lib</outputDirectory>
</dependencySet>
<dependencySet>
<unpack>true</unpack>
<includes>
<include>mypackage.static:server:*</include>
</includes>
<useProjectArtifact>false</useProjectArtifact>
<outputDirectory>/</outputDirectory>
</dependencySet>
<dependencySet>
<unpack>false</unpack>
<includes>
<include>*</include>
</includes>
<excludes>
<exclude>mypackage.*</exclude>
</excludes>
<scope>runtime</scope>
<useProjectArtifact>false</useProjectArtifact>
<outputDirectory>Web-inf/lib</outputDirectory>
</dependencySet>
</dependencySets>

Answer 1

The maven-assembly-plugin is not intended to create a war. For this purpose use the maven-war-plugin instead.
If you need to create war files for different environments like test,qa, production. This can be used as well a base for different app servers. But if we are talking about a application server this means we should create ear files instead of war files (This means to use maven-ear-plugin instead of maven-war-plugin).
|-- pom.xml
`-- src
|-- main
| |-- java
| |-- resources
| |-- environment
| | |-- test
| | | `-- database.properties
| | |-- qa
| | | `-- database.properties
| | `-- production
| | `-- database.properties
| `-- webapp
You need the following assembly for that (for every environment) which can be created based on this as a template:
<assembly xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0 http://maven.apache.org/xsd/assembly-1.1.0.xsd">
<id>test</id>
<formats>
<format>war</format>
</formats>
<includeBaseDirectory>false</includeBaseDirectory>
<dependencySets>
<dependencySet>
<unpack>true</unpack>
<useProjectArtifact>true</useProjectArtifact>
</dependencySet>
</dependencySets>
<fileSets>
<fileSet>
<outputDirectory>WEB-INF</outputDirectory>
<directory>${basedir}/src/main/environment/test/</directory>
<includes>
<include>**</include>
</includes>
</fileSet>
</fileSets>
</assembly>
To support different artifacts for different environments this is the time for the maven-assembly-plugin like this:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<id>test</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptors>
<descriptor>${project.basedir}/src/main/assembly/test.xml</descriptor>
</descriptors>
</configuration>
</execution>
<execution>
<id>qa</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptors>
<descriptor>${project.basedir}/src/main/assembly/qa.xml</descriptor>
</descriptors>
</configuration>
</execution>
<execution>
<id>production</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptors>
<descriptor>${project.basedir}/src/main/assembly/production.xml</descriptor>
</descriptors>
</configuration>
</execution>
</executions>
</plugin>
The result is creating three different war files which can be distinguished by their appropriate classifier with a single call (detailed description can be read here):
mvn clean package