Appendix D. Deploying a Spring Boot application using WAR files

As an alternative to the supported application packaging and deployment workflow using fat JAR files, you can package and deploy a Spring Boot application as a WAR (Web Application Archive) file. You must configure your build and deployment settings to ensure that your application builds and deploys correctly on OpenShift.

Prerequisites

  • A Spring Boot application, such as an example.
  • Fabric8 Maven Plugin used to deploy your application to OpenShift.
  • Spring Boot Maven Plugin used to package your application.

Procedure

  1. Add war packaging to the pom.xml file of your project:

    Example pom.xml

    <project ...>
      ...
      <packaging>war</packaging>
      ...
    </project>

  2. Specify spring-boot-starter-tomcat as a dependency of your application:

    Example pom.xml

    <project ...>
      ...
      <dependencies>
        ...
        <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-tomcat</artifactId>
        </dependency>
        ...
      </dependencies>
      ...
    </project>

  3. Ensure the repackage Maven goal for the Spring Boot Maven plugin is defined in the pom.xml file:

    Example pom.xml

    <project ...>
    ...
      <build>
        ...
        <plugins>
          ...
          <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <executions>
              <execution>
                <goals>
                  <goal>repackage</goal>
                </goals>
              </execution>
            </executions>
          </plugin>
        </plugins>
      </build>
    ...
    </project>

    This ensures that the Spring Boot classes used to launch the application are included in the WAR file, and that the corresponding properties for these classes are defined in the MANIFEST.mf file of the WAR file:

    • Main-Class: org.springframework.boot.loader.WarLauncher
    • Spring-Boot-Classes: WEB-INF/classes/
    • Spring-Boot-Lib: WEB-INF/lib/
    • Spring-Boot-Version: 2.1.6.RELEASE
  4. Add the ARTIFACT_COPY_ARGS environment variable to the pom.xml file.

    The Fabric8 Maven Plugin consumes this variable during the build process and ensures that the Build and Deploy tool uses the WAR file (rather than the default fat JAR file) to create the application container image:

    Example pom.xml

        ...
        <profile>
          <id>openshift</id>
          <build>
            <plugins>
              <plugin>
                <groupId>io.fabric8</groupId>
                <artifactId>fabric8-maven-plugin</artifactId>
                <executions>
                  ...
                </executions>
                <configuration>
                    <images>
                        <image>
                            <name>${project.artifactId}:%t</name>
                            <alias>${project.artifactId}</alias>
                            <build>
                                <from>registry.access.redhat.com/redhat-openjdk-18/openjdk18-openshift:${openjdk18-openshift.version}</from>
                                <assembly>
                                    <basedir>/deployments</basedir>
                                    <descriptorRef>artifact</descriptorRef>
                                </assembly>
                                <env>
                                    <ARTIFACT_COPY_ARGS>*.war</ARTIFACT_COPY_ARGS>
                                    <JAVA_APP_DIR>/deployments</JAVA_APP_DIR>
                                </env>
                                <ports>
                                    <port>8080</port>
                                </ports>
                            </build>
                        </image>
                    </images>
                </configuration>
              </plugin>
            </plugins>
          </build>
        </profile>
        ...

  5. Add the JAVA_APP_JAR environment variable to the src/main/fabric8/deployment.yml file.

    This variable instructs the Fabric8 Maven Plugin to launch your application using the WAR file included with the container. If src/main/fabric8/deployment.yml does not exist, you can create it.

    Example deployment.yml

    spec:
      template:
        spec:
          containers:
            ...
              env:
              - name: JAVA_APP_JAR
                value: ${project.artifactId}-${project.version}.war

  6. Build and deploy your application:

    mvn clean fabric8:deploy -Popenshift