Add external resource directories to jar using build-helper-maven-plugin

This post demonstrates how to add directories that contain resources needed by an application using build-helper-maven-plugin via Maven.

Simple Cases

In simple cases, resources like .properties and XSDs go with project codes. Consider the following Maven project that builds a codebase into an executable jar file.

When we mvn clean package our application, we’ll have the following contents of the jar file. Those clients-config-* directories become readily available to codes that come along with the jar file.

External Resource Directories

In this section, we try to externalize the clients-config-* resource directories. First, we move them to some external directory or directory that will not be read from during the build process.

If we mvn clean package our application without changing anything else, the content of our jar file is as follows.

mvn clean package

1	mvn clean package

Using build-helper-maven-plugin plugin

To include all clients-config-* directory from somewhere-external, we need to use a Maven plugin – build-helper-maven-plugin. This requires modifying our pom.xml to

...
<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
		</plugin>
		<plugin>
			<groupId>org.codehaus.mojo</groupId>
			<artifactId>build-helper-maven-plugin</artifactId>
			<executions>
				<execution>
					<id>addExternalAllClientsConfigDirectories</id>
					<phase>generate-resources</phase>
					<goals>
						<goal>add-resource</goal>
					</goals>
					<configuration>
						<resources>
							<resource>
								<directory>${project.basedir}/somewhere-external</directory>
							</resource>
						</resources>
					</configuration>
				</execution>
			</executions>
		</plugin>
	</plugins>
</build>
...