How can I merge resource files in a Maven assembly?

Question

I\'m using Maven and its assembly plugin to build a distribution package of my project like this:

• one project assembles a basic runtime (based on Felix), with

Answer 1

Expanding a bit on Juergen's answer for those who stumble on this - the containerDescriptorHandler in the descriptor can take four values (v2.3), these are metaInf-services, file-aggregator, plexus, metaInf-spring. It's a bit buried in the code (found in the package org.apache.maven.plugin.assembly.filter) but it is possible to aggregate config/properties files.

Here's an example descriptor that aggregates the META-INF/services and named property files located in com.mycompany.actions.

descriptor.xml

...



    
        metaInf-services
    

    
        file-aggregator
        
            com/mycompany/actions/action.properties
            com/mycompany/actions/action.properties
        
    



....

The file-aggregator can contain a regular expression in the filePattern to match multiple files. The following would match all files names 'action.properties'.

.+/action.properties

The metaInf-services and metaInf-spring are used for aggregating SPI and spring config files respectively whilst the plexus handler will aggregate META-INF/plexus/components.xml together.

If you need something more specialised you can add your own configuration handler by implementing ContainerDescriptorHandler and defining the component in META-INF/plexus/components.xml. You can do this by creating an upstream project which has a dependency on maven-assembly-plugin and contains your custom handler. It might be possible to do this in the same project you're assembling but I didn't try that. Implementations of the handlers can be found in org.apache.maven.plugin.assembly.filter.* package of the assembly source code.

CustomHandler.java

package com.mycompany;

import org.apache.maven.plugin.assembly.filter.ContainerDescriptorHandler;

public class CustomHandler implements ContainerDescriptorHandler {
    // body not shown
}

then define the component in /src/main/resources/META-INF/plexus/components.xml

components.xml

    
        
            org.apache.maven.plugin.assembly.filter.ContainerDescriptorHandler
            custom-handler
            com.mycompany.CustomHandler
            per-lookup
        
    

Finally you add this as a dependency on the assembly plugin in the project you wish to assemble

pom.xml

    org.apache.maven.plugins
    maven-assembly-plugin
    2.2.1
    
        
            ...
        
    
    
        
            com.mycompany
            sample-handler
            1.0
        
    

and define the handlerName in the descriptor

descriptor.xml

...

    custom-handler

...

The maven-shade-plugin can also create 'uber-jars' and has some resource transforms for handling XML, licences and manifests.

J