Welcome to Geoff Hayward's Weblog

Maven: Packaging Dockerfile's with variables
03 October 2018

This post is a note on using Maven's 'maven-antrun-plugin' to replace a variable version number in a Dockerfile with the Maven project's version.

The following code replaces this line ADD ./target/application-@{version}.jar application.jar in a Dockerfile with something like ADD ./target/application-1.2.0-SNAPSHOT.jar application.jar. The processed Dockerfile is then saved in the target folder alongside any other artefacts created by Maven.

<plugin>
    <artifactId>maven-antrun-plugin</artifactId>
    <version>1.8</version>
    <executions>
        <execution>
            <phase>package</phase>
            <configuration>
                <target>
                    <copy file="Dockerfile" todir="${project.build.directory}"/>
                    <replace file="${project.build.directory}/Dockerfile" >
                        <replacefilter token="@{version}" value="${project.version}" />
                    </replace>
                </target>
            </configuration>
            <goals>
                <goal>run</goal>
            </goals>
        </execution>
    </executions>
</plugin>

Once the Dockerfile has been processed a tool such as the Maven 'maven-assembly-plugin' can then package the Dockerfile and other artefacts into a shippable form.

For completeness, here is an example configuration that creates a shippable ZIP ready for AWS's Elastic Beanstalk.

<plugin>
    <artifactId>maven-assembly-plugin</artifactId>
    <version>3.0.0</version>
    <executions>
        <execution>
            <id>make-zip</id>
            <phase>package</phase>
            <goals>
                <goal>single</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <appendAssemblyId>false</appendAssemblyId>
        <descriptors>
            <descriptor>assembly.xml</descriptor>
        </descriptors>
    </configuration>
</plugin>

And here is the corresponding example of the 'filesSets' element from an assembly.xml.

<fileSets>
    <fileSet>
        <directory>${project.build.directory}</directory>
        <includes>
            <include>${project.build.finalName}.jar</include>
        </includes>
        <outputDirectory>target</outputDirectory>
    </fileSet>
    <fileSet>
        <directory>${project.build.directory}</directory>
        <includes>
            <include>Dockerfile</include>
        </includes>
        <outputDirectory>.</outputDirectory>
    </fileSet>
    <fileSet>
        <directory>${basedir}</directory>
        <includes>
            <-- other stuff from the base directory -->
        </includes>
        <outputDirectory>.</outputDirectory>
    </fileSet>
</fileSets>

I hope this helps you.

Jetty: getting JSP's to compile on Java 8
25 July 2015

I have been trying to put an older embedded Jetty served application onto Java 8. The application's JSP files where, however, not compiling. This delayed having the benefits Java 8 brings to development.

After a lot of digging I discovered that the Mavan 'org.mortbay.jetty' namespace (a.k.a. groupid) had been superseded by 'org.eclipse.jetty'. The newer development and fixes by the Jetty project are in the later namespace. Therefore, by replacing the old 'org.mortbay.jetty' dependency:

<dependency>
    <groupId>org.mortbay.jetty</groupId>
    <artifactId>jsp-2.1-glassfish</artifactId>
  <version>9.1.02.B04.p0</version>
</dependency>

with the new 'org.eclipse.jetty'. dependency:

<dependency>
  <groupId>org.eclipse.jetty</groupId>
    <artifactId>jetty-jsp</artifactId>
  <version>9.3.0.M1</version>
</dependency>

the JSP's compile and the older project now works with Java 8.