<dependency>
  <groupId>org.apache.tomcat.embed</groupId>
  <artifactId>tomcat-embed-core</artifactId>
  <version>${tomcat.version}</version>
</dependency>

<dependency>
  <groupId>org.apache.tomcat.embed</groupId>
  <artifactId>tomcat-embed-jasper</artifactId>
  <version>${tomcat.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.tomcat</groupId>
  <artifactId>tomcat-jasper</artifactId>
  <version>${tomcat.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.tomcat</groupId>
  <artifactId>tomcat-jasper-el</artifactId>
  <version>${tomcat.version}</version>
</dependency>

<dependency>
  <groupId>org.glassfish.jersey.media</groupId>
  <artifactId>jersey-media-json-jackson</artifactId>
  <version>${jersey2.version}</version>
</dependency>

<dependency>
  <groupId>org.glassfish.jersey.containers</groupId>
  <artifactId>jersey-container-servlet</artifactId>
  <version>${jersey2.version}</version>
</dependency>

<dependency>
  <groupId>org.glassfish.jersey.inject</groupId>
  <artifactId>jersey-hk2</artifactId>
  <version>${jersey2.version}</version>
</dependency>

<dependency>
  <groupId>org.glassfish.jersey.bundles</groupId>
  <artifactId>jaxrs-ri</artifactId>
  <version>${jersey2.version}</version>
</dependency>

<dependency>
  <groupId>org.glassfish.hk2</groupId>
  <artifactId>hk2-extras</artifactId>
  <version>${hk2.version}</version>
</dependency>

public class EmailApplication
{
  private static final Logger LOGGER = LoggerFactory.getLogger(EmailApplication.class);

  public static void main(String[] args) {
    try {
      start();
    } catch (Exception e) {
      LOGGER.error("ITZap Email application failed to run", e);
    }
  }

  private static void start() throws Exception {

    String contextPath = "";
    String appBase = ".";
    String port = System.getenv("PORT");
    if (port == null || port.isEmpty()) {
      port = "8025";
    }

    Tomcat tomcat = new Tomcat();
    tomcat.setPort(Integer.parseInt(port));
    tomcat.getHost().setAppBase(appBase);

    Context context = tomcat.addWebapp(contextPath, appBase);

    Tomcat.addServlet(context, "jersey-container-servlet",
                      new ServletContainer(resourceConfig()));
    context.addServletMappingDecoded(UDecoder.URLDecode("/v1/itzap/message/*", Charset.defaultCharset()),
                                     "jersey-container-servlet");

    // initialize Tomcat. (Since version 9.xx need to add tomcat.getConnector() here)
    tomcat.getConnector();
    tomcat.start();
    tomcat.getServer().await();
  }

  private static ResourceConfig resourceConfig() {
    return new JerseyConfig();
  }
}

public final class Factories {
  private static final Config CONFIG = ConfigFactory.load();

  private Factories() {}

  public static class MailServiceFactory extends AbstractFactory<EMailService> {
    public MailServiceFactory() {
    }

    @Override
    public EMailService provide() {
      return new EMailService(CONFIG);
    }
  }
}

public class JerseyConfig extends ResourceConfig {
  JerseyConfig() {
    register(JacksonFeature.class);

    // register endpoints
    packages("com.itzap.message.rest");

    register(new ContainerLifecycleListener()
             {
               public void onStartup(Container container)
               {
                 // access the ServiceLocator here
                 // serviceLocator = container.getApplicationHandler().
                 ServiceLocator serviceLocator = ((ImmediateHk2InjectionManager)container
                                                  .getApplicationHandler().getInjectionManager()).getServiceLocator();
                 enableTopicDistribution(serviceLocator);
                 // ... do what you need with ServiceLocator ...
               }

               public void onReload(Container container) {/*...*/}
               public void onShutdown(Container container) {/*...*/}
             });

    register(new AbstractBinder() {
      @Override
      protected void configure() {
        // hk2 bindings
        bindFactory(Factories.MailServiceFactory.class)
          .to(EMailService.class)
          .in(Singleton.class);
      }
    });
  }
}

@Provider
public class IZapExceptionMapper implements ExceptionMapper<IZapException> {
  @Override
  public Response toResponse(IZapException e) {
    ErrorResponse response = MapperUtils.toReturn(e);

    return Response.status(response.getStatus())
      .entity(response)
      .type(MediaType.APPLICATION_JSON_TYPE)
      .build();
  }
}

<dependency>
  <groupId>com.typesafe</groupId>
  <artifactId>config</artifactId>
</dependency>

private static final Config CONFIG = ConfigFactory.load();
// do some stuff
String emailFrom = CONFIG.getString("email.from");
  

<plugin>
  <artifactId>maven-assembly-plugin</artifactId>
  <version>3.0.0</version>
  <executions>
    <execution>
      <id>make-assembly</id> <!-- this is used for inheritance merges -->
      <phase>package</phase> <!-- bind to the packaging phase -->
      <goals>
        <goal>single</goal>
      </goals>
    </execution>
  </executions>
  <configuration>
    <archive>
      <manifest>
        <mainClass>com.itzap.message.app.EmailApplication</mainClass>
      </manifest>
    </archive>
    <descriptors>
      <descriptor>src/main/resources/assembly/itzap-message.xml</descriptor>
    </descriptors>
    <appendAssemblyId>false</appendAssemblyId>
  </configuration>
</plugin>

<assembly xmlns="http://maven.apache.org/ASSEMBLY/2.0.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/ASSEMBLY/2.0.0 http://maven.apache.org/xsd/assembly-2.0.0.xsd">
    <id>itzap-message</id>
    <formats>
        <format>jar</format>
    </formats>

    <includeBaseDirectory>false</includeBaseDirectory>
    <fileSets>
        <fileSet>
            <directory>src</directory>
            <excludes>
                <exclude>**</exclude>
            </excludes>
        </fileSet>
    </fileSets>

    <dependencySets>
        <dependencySet>
            <unpack>true</unpack>
            <unpackOptions>
                <excludes>
                    <exclude>*.log</exclude>
                    <exclude>assembly/**</exclude>
                    <exclude>databases/**</exclude>
                </excludes>
            </unpackOptions>
        </dependencySet>
    </dependencySets>
</assembly>

version: '3.2'

services:

  mail:
    image: boky/postfix
    environment:
      ALLOWED_SENDER_DOMAINS: ${ALLOWED_DOMAINS}

    ports:
      - 1587:587

  message:
    # Builds message service
    build: "."
    image: message-service:latest
    environment:

      MAIL_HOST: mail
      MAIL_FROM: ${MAIL_FROM}
    privileged: true
    ports:
      - 8025:8025
    links:
      - mail

    depends_on:
      - mail

# Alpine Linux with OpenJDK JRE
FROM openjdk:8-jre-alpine
COPY message-impl/target/message-impl-0.0.1-SNAPSHOT.jar /opt/lib/
ENTRYPOINT ["/usr/bin/java"]
CMD ["-jar", "/opt/lib/message-impl-0.0.1-SNAPSHOT.jar"]
EXPOSE 8025