A simple web servlet in Jersey

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
                      http://maven.apache.org/xsd/maven-4.0.0.xsd">

  <modelVersion>4.0.0</modelVersion>
  <groupId>com.windofkeltia.melissa-data</groupId>
  <artifactId>melissa-data</artifactId>
  <version>1.0.0</version>
  <packaging>war</packaging>

  <!--
    To build the WAR file, do mvn clean package.
    -->
  <properties>
    <wokprefix>windofkeltia</wokprefix>
    <wokversion>0</wokversion>
    <wokrelease>0</wokrelease>
    <tomcat.version>9.0.7</tomcat.version>
    <jersey2.version>2.27</jersey2.version>
    <jersey-bundle.version>1.19.1</jersey-bundle.version>
    <jaxrs.version>2.0.1</jaxrs.version>
    <servlet-api.version>4.0.0</servlet-api.version>
    <slf4j.version>1.7.7</slf4j.version>
    <log4j.version>1.2.17</log4j.version>
    <junit.version>4.12</junit.version>
    <maven-compiler-plugin.version>3.2</maven-compiler-plugin.version>
    <maven-war-plugin.version>3.2.0</maven-war-plugin.version>
    <maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>com.sun.jersey</groupId>
      <artifactId>jersey-bundle</artifactId>
      <version>${jersey-bundle.version}</version>
    </dependency>
    <dependency>
      <groupId>javax.activation</groupId>
      <artifactId>activation</artifactId>
      <version>1.1.1</version>
    </dependency>
    <dependency>
      <groupId>javax.xml.bind</groupId>
      <artifactId>jaxb-api</artifactId>
      <version>2.3.0</version>
    </dependency>
    <dependency>
      <groupId>org.apache.tomcat</groupId>
      <artifactId>tomcat-servlet-api</artifactId>
      <version>${tomcat.version}</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>${servlet-api.version}</version>
    </dependency>
    <!-- Various other dependencies -->
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>${slf4j.version}</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>${slf4j.version}</version>
    </dependency>
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>${log4j.version}</version>
    </dependency>
  </dependencies>

  <build>
    <finalName>melissa-data</finalName>
    <pluginManagement>
    </pluginManagement>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
        <version>${maven-compiler-plugin.version}</version>
      </plugin>
      <!-- what builds a WAR file -->
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-war-plugin</artifactId>
        <version>${maven-war-plugin.version}</version>
        <configuration>
          <webResources>
            <resource>
              <!-- this is relative to the same directory as pom.xml -->
              <directory>src/main/webapp</directory>
            </resource>
          </webResources>

          <!-- Magic for maintaining a build timestamp in MANIFEST.MF: -->
          <archive>
            <manifest>
              <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
              <addDefaultSpecificationEntries>true</addDefaultSpecificationEntries>
            </manifest>
            <manifestEntries>
              <Build-Time>${maven.build.timestamp}</Build-Time>
            </manifestEntries>
          </archive>
        </configuration>
      </plugin>
      <!-- how to echo out properties and their definitions -->
      <plugin>
        <artifactId>maven-antrun-plugin</artifactId>
        <version>1.8</version>
        <executions>
          <execution>
            <phase>compile</phase>
            <configuration>
              <target>
                <!-- <echoproperties /> -->
              </target>
            </configuration>
            <goals>
              <goal>run</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>${maven-surefire-plugin.version}</version>
        <configuration>
          <systemPropertyVariables>
            <catalina.home>${project.build.directory}</catalina.home>
            <buildDirectory>${project.build.directory}</buildDirectory>
          </systemPropertyVariables>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                             http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
  <display-name>melissa-data</display-name>

  <servlet>
    <servlet-name>melissa-data</servlet-name>
    <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>

    <init-param>
      <param-name>com.sun.jersey.config.property.packages</param-name>
      <param-value>com.windofkeltia.servlet</param-value>
    </init-param>

    <init-param>
      <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
      <param-value>true</param-value>
    </init-param>
  </servlet>

  <listener>
    <listener-class>com.windofkeltia.servlet.ServletInitializer</listener-class>
  </listener>

  <servlet-mapping>
    <servlet-name>melissa-data</servlet-name>
    <url-pattern>/*</url-pattern>
  </servlet-mapping>
</web-app>

package com.windofkeltia.servlet;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

@Path( "" )
public class MelissaDataServlet extends HttpServlet
{
  private String           message;
  private static final int STATUS_500 = Response.Status.INTERNAL_SERVER_ERROR.getStatusCode();

  @GET
  @Produces( MediaType.TEXT_PLAIN )
  public String getStatusInPlainText( @Context HttpServletRequest request )
  {
    return MelissaDataStatus.getStatusInPlainText( MelissaDataStatus.readManifest( request.getServletContext() ) );
  }

  @POST
  @Consumes( { MediaType.TEXT_XML, MediaType.APPLICATION_XML } )
  @Produces( { MediaType.TEXT_XML, MediaType.APPLICATION_XML } )
  public Response postRequest( @Context HttpServletRequest request, @Context HttpHeaders header )
  {
    return null; // ServiceImpl.post( request, header ); TODO: implement this after GET works!
  }
}

package com.windofkeltia.servlet;

import javax.servlet.ServletContext;
import java.io.IOException;
import java.util.Calendar;
import java.util.jar.Attributes;
import java.util.jar.Manifest;

import static java.util.Objects.nonNull;

public class MelissaDataStatus
{
  private static final String COPYRIGHT  = "Copyright ";
  private static final String COPY_PLAIN = "(c) ";
  private static final String COMPANY    = "by Wind of Keltia, LLC.";
  private static final String RIGHTS     = "Proprietary and confidential. All rights reserved.";
  private static final String PURPOSE    = "Delivers Melissa Data from its server to HTTP clients.";

  protected static String getStatusInPlainText( final String MANIFEST )
  {
    StringBuilder sb = new StringBuilder();
    sb.append( "The Melissa Data service is up.\n\n" );
    sb.append( MANIFEST ).append( '\n' );
    sb.append( PURPOSE ).append( "\n\n" );
    sb.append( COPYRIGHT ).append( COPY_PLAIN ).append( getYearRange() ).append( ' ' ).append( COMPANY ).append( '\n' );
    sb.append( RIGHTS ).append( '\n' );
    return sb.toString();
  }

  private static String getYearRange()
  {
    final String FIRST_YEAR = "2018";   // just pretending I've been at this for a couple of years
    int          current    = Calendar.getInstance().get( Calendar.YEAR );
    String       YEAR_RANGE = FIRST_YEAR;

    if( current > Integer.parseInt( FIRST_YEAR ) )
      YEAR_RANGE += "-" + current;

    return YEAR_RANGE;
  }

  protected static String readManifest( ServletContext servletContext )
  {
    StringBuilder sb         = new StringBuilder();
    boolean       htmlBreaks = false;

    try
    {
      Manifest   manifest   = new Manifest( servletContext.getResourceAsStream( "/META-INF/MANIFEST.MF" ) );
      Attributes attributes = manifest.getMainAttributes();
      String     line;

      if( isNotEmpty( line = attributes.getValue( "Manifest-Version" ) ) )
        sb.append( "        Manifest-Version: " ).append( line ).append( '\n' );
      if( isNotEmpty( line = attributes.getValue( "Implementation-Title" ) ) )
        sb.append( "    Implementation-Title: " ).append( line ).append( '\n' );
      if( isNotEmpty( line = attributes.getValue( "Implementation-Version" ) ) )
        sb.append( "  Implementation-Version: " ).append( line ).append( '\n' );
      // this is something like "Built-By: russ" or buildbot, etc.
      //      if( !isEmpty( line = attributes.getValue( "Built-By" ) ) )
      //        sb.append( "               Built-By: " ).append( line ).append( '\n' );
      if( isNotEmpty( line = attributes.getValue( "Specification-Title" ) ) )
        sb.append( "     Specification-Title: " ).append( line ).append( '\n' );
      if( isNotEmpty( line = attributes.getValue( "Implementation-Vendor-Id" ) ) )
        sb.append( "Implementation-Vendor-Id: " ).append( line ).append( '\n' );
      if( isNotEmpty( line = attributes.getValue( "Build-Time" ) ) )
        sb.append( "              Build-Time: " ).append( line ).append( '\n' );
      if( isNotEmpty( line = attributes.getValue( "Created-By" ) ) )
        sb.append( "              Created-By: " ).append( line ).append( '\n' );
      if( isNotEmpty( line = attributes.getValue( "Build-Jdk" ) ) )
        sb.append( "               Build-JDK: " ).append( line ).append( '\n' );
      if( isNotEmpty( line = attributes.getValue( "Specification-Version" ) ) )
        sb.append( "   Specification-Version: " ).append( line ).append( '\n' );

      return sb.toString();
    }
    catch( IOException ex )
    {
      return "Application build timestamp unavailable";
    }
  }

  private static boolean isNotEmpty( final String string ) { return( nonNull( string ) && string.length() > 0 ); }
}

package com.windofkeltia.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.apache.log4j.Logger;

/**
 * Initialize when the application starts. The way you get this code called
 * is by adding this to web/WEB-INF/web.xml:
 *
 * <pre>
 * <listener>
 *   <listener-class>
 *     com.windofkeltia.servlet.ServletInitializer
 *   </listener-class>
 * </listener>
 * </pre>
 * @author Russell Bateman
 */
public class ServletInitializer implements ServletContextListener
{
  private static final Logger log = Logger.getLogger( ServletInitializer.class );

  /**
   * This method is called when the servlet context is initialized (when the
   * web application is deployed). You can initialize servlet context-related
   * data here. We use this listener to ensure that we're all up and running
   * before any of the services get registered.
   */
  @Override
  public void contextInitialized( ServletContextEvent event )
  {
    ServletContext     context  = event.getServletContext();
    MelissaDataServlet instance = new MelissaDataServlet();
    final String COPYRIGHT_AND_STATUS = MelissaDataStatus.readManifest( context );
    log.info( "#############################################################" );
    log.info( "Initializing melissa-data application context..." );
    log.info( MelissaDataStatus.getStatusInPlainText( COPYRIGHT_AND_STATUS ) );
  }

  /**
   * This method is invoked when the Servlet Context (the web application) is
   * undeployed or the (Tomcat) server shuts down.
   */
  @Override
  public void contextDestroyed( ServletContextEvent event )
  {
    log.info( "Discarded melissa-data application context!" );
  }
}