Camel Repackager Maven Plugin

This Maven plugin creates self-executing JARs using Spring Boot's loader tools, providing the same nested JAR structure that Spring Boot uses for its executable JARs.

Overview

Instead of creating traditional "fat JARs" where all dependencies are unpacked and merged into a single JAR (like maven-shade-plugin does), this plugin creates JARs with Spring Boot's nested structure:

example.jar
 |
 +-META-INF
 |  +-MANIFEST.MF
 +-org
 |  +-springframework
 |     +-boot
 |        +-loader
 |           +-<spring boot loader classes>
 +-BOOT-INF
    +-classes
    |  +-<your application classes>
    +-lib
       +-dependency1.jar
       +-dependency2.jar

Benefits

Faster startup: No need to unpack all dependencies
Better memory usage: Dependencies are loaded on-demand
Avoids classpath conflicts: Preserves original JAR signatures and avoids file conflicts
Smaller memory footprint: Only loads classes that are actually used
Better debugging: Easier to identify which JAR a class comes from

Usage

Add the plugin to your pom.xml:

xml

<plugin>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-repackager-maven-plugin</artifactId>
    <version>${camel.version}</version>
    <executions>
        <execution>
            <id>repackage-executable</id>
            <phase>package</phase>
            <goals>
                <goal>repackage</goal>
            </goals>
            <configuration>
                <mainClass>com.example.MyMainClass</mainClass>
            </configuration>
        </execution>
    </executions>
</plugin>

Configuration

Parameter	Description	Default	Required
`mainClass`	The main class to use for the executable JAR		Yes
`sourceJar`	The source JAR file to repackage	`${project.build.directory}/${project.build.finalName}.jar`	No
`outputDirectory`	The output directory for the repackaged JAR	`${project.build.directory}`	No
`finalName`	The final name of the repackaged JAR (without extension)	`${project.build.finalName}`	No
`backupSource`	Whether to backup the source JAR	`true`	No

How it works

The plugin takes your regular JAR file (containing just your application classes)
Uses Spring Boot's Repackager class to create the nested structure
Includes all compile and runtime dependencies as separate JARs in BOOT-INF/lib/
Adds Spring Boot's loader classes to handle the nested JAR loading
Sets up the manifest to use JarLauncher as the main class and your class as Start-Class

Comparison with maven-shade-plugin

Aspect	maven-shade-plugin	camel-repackager
JAR Structure	Single flat JAR with all classes	Nested JARs with Spring Boot loader
Startup Time	Slower (all classes loaded)	Faster (on-demand loading)
Memory Usage	Higher (all classes in memory)	Lower (only used classes loaded)
Classpath Conflicts	Possible (overlapping files)	Avoided (separate JARs)
Debugging	Harder (merged classes)	Easier (original JAR structure)
File Size	Smaller (no duplication)	Slightly larger (loader overhead)

Example

See the Camel JBang launcher (dsl/camel-jbang/camel-launcher) for a real-world example of how this plugin is used.