Custom maven assembly - maven-2

Question

I'm starting to work with Maven but am not yet successfully thinking in Maven's terms. I have a specific requirement and the docs aren't giving me enough clues, so I could use a bit of help:
I'd like to create an assembly that
builds a jar-with-dependencies like the "standard" target of this name, but excluding a couple of the resources. I want log4j.properties and a couple of other configuration files to not be in the jar.
builds a .ZIP file containing in its root directory the .jar from step 1 as well as the above mentioned config files.
I want to fire this assembly up from the command line (only), hence no need to tie to a phase (or goal? mojo?). Preferrably using either assembly:assembly or assembly:single.
Do I need a custom assembly descriptor for this?
And is it true I can't nest it in the pom.xml? So it goes in src/assembly/something.xml and gets referenced with a descriptorRef?
Can I code this as two relatively simple assemblies, of which one builds on the other (i.e. the .Zip assembly uses the .Jar assembly) or do I have to do everything in one assembly?

Answer 1

I'm starting to work with Maven but am not yet successfully thinking in Maven's terms.
Welcome on board, Carl! :D
I want to fire this assembly up from the command line (only), hence no need to tie to a phase (or goal? mojo?). Preferrably using either assembly:assembly or assembly:single.
Just to clarify: the build lifecycle itself is made of phases (compile, test, package, etc) and plugin goals (technically Mojos) are bound on phases. You then either invoke a phase... or just a specific plugin goal.
Do I need a custom assembly descriptor for this?
Well, since you want behavior that the pre-defined descriptors don't cover, yes. You'll even need two of them (of for the uberjar, one for the zip).
And is it true I can't nest it in the pom.xml? So it goes in src/assembly/something.xml and gets referenced with a descriptorRef?
Yes, that's true (descriptors use a custom format) and they usually go into src/main/assembly. And no, descriptorRef is for the built-in descriptors, you'll have to use descriptor here.
Can I code this as two relatively simple assemblies, of which one builds on the other (i.e. the .Zip assembly uses the .Jar assembly) or do I have to do everything in one assembly?
As hinted, you'll need two assembly descriptors. Let me help a bit...
Let's assume you have the following project structure:
$ tree .
.
├── pom.xml
└── src
├── main
│   ├── assembly
│   │   ├── jar.xml
│   │   └── zip.xml
│   ├── java
│   │   └── com
│   │   └── stackoverflow
│   │   └── App.java
│   └── resources
│   └── log4j.properties
└── test
└── java
└── com
└── stackoverflow
└── AppTest.java
Where the pom.xml contains the following configuration for the assembly plugin:
<project>
...
<dependencies>
...
</dependencies>
...
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.2-beta-5</version>
<configuration>
<descriptors>
<descriptor>src/main/assembly/jar.xml</descriptor>
<descriptor>src/main/assembly/zip.xml</descriptor>
</descriptors>
</configuration>
</plugin>
</plugins>
</build>
</project>
The descriptor for the "filtered" uberjar (jar.xml) looks like this:
<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>uberjar</id>
<formats>
<format>jar</format>
</formats>
<includeBaseDirectory>false</includeBaseDirectory>
<dependencySets>
<dependencySet>
<unpack>true</unpack>
<scope>runtime</scope>
<useProjectArtifact>false</useProjectArtifact>
</dependencySet>
</dependencySets>
<fileSets>
<fileSet>
<directory>${project.build.outputDirectory}</directory>
<outputDirectory>/</outputDirectory>
<excludes>
<exclude>log4j.properties</exclude>
</excludes>
</fileSet>
</fileSets>
</assembly>
What this descriptor does is (in short):
include the dependencies, unpack them, but exclude the project itself (yes, this is counter intuitive but this weird default behavior has been kept for backward compatibility)
include the project files but exclude some of them.
And the descriptor for the zip (zip.xml) looks like this:
<assembly xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0 http://maven.apache.org/xsd/assembly-1.1.0.xsd">
<id>bin</id>
<formats>
<format>zip</format>
</formats>
<includeBaseDirectory>false</includeBaseDirectory>
<fileSets>
<fileSet>
<directory>${project.basedir}/src/main/resources</directory>
<outputDirectory/>
<includes>
<include>log4j.properties</include>
</includes>
</fileSet>
<fileSet>
<directory>${project.build.directory}</directory>
<outputDirectory/>
<includes>
<include>*-uberjar.jar</include>
</includes>
</fileSet>
</fileSets>
</assembly>
Which is (somehow) self explaining :)
it includes the configuration files (relatively to <directory>) at the root of the assembly
it includes the uberjar (relatively to <directory>) at the root of the assembly
Finally, just run mvn assembly:assembly (that's the goal intended to be used on the CLI).
I didn't (knowingly) include META-INF/maven/** in the assembly for the uberjar. Is there a simple way to prevent inclusion of these?
These are coming from the libraries that are unpacked. You can exclude them using unpackOptions. Here is a modified version of the jar.xml:
<assembly xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0 http://maven.apache.org/xsd/assembly-1.1.0.xsd">
<id>uberjar</id>
<formats>
<format>jar</format>
</formats>
<includeBaseDirectory>false</includeBaseDirectory>
<dependencySets>
<dependencySet>
<unpack>true</unpack>
<scope>runtime</scope>
<unpackOptions>
<excludes>
<exclude>META-INF/maven/**</exclude>
</excludes>
</unpackOptions>
<useProjectArtifact>false</useProjectArtifact>
</dependencySet>
</dependencySets>
<fileSets>
<fileSet>
<directory>${project.build.outputDirectory}</directory>
<outputDirectory>/</outputDirectory>
<excludes>
<exclude>log4j.properties</exclude>
</excludes>
</fileSet>
</fileSets>
</assembly>